Bulletin of the American Physical Society
61st Annual Meeting of the APS Division of Plasma Physics
Volume 64, Number 11
Monday–Friday, October 21–25, 2019; Fort Lauderdale, Florida
Session NP10: Poster Session V: Basic Plasmas: Theory, Computation, Reconnection, Shocks. Dusty Plasmas, Low Temperature Plasmas (9:30am12:30pm) 
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Room: Exhibit Hall A 

NP10.00001: Symplectic gyrokinetic VlasovMaxwell theory Alain Brizard A new representation of electromagnetic gyrokinetic VlasovMaxwell theory is considered in which the gyrocenter symplectic structure contains the electric and magnetic field perturbations needed to yield the standard gyrocenter polarization and magnetization terms appearing in the gyrokinetic Maxwell equations. The gyrocenter Hamilton equations, which are expressed in terms of a timedependent gyrocenter Jacobian and a gyrocenter Poisson bracket that contains electromagnetic field perturbations, satisfy the Liouville property exactly. The selfconsistent gyrokinetic VlasovMaxwell equations are derived from a variational principle, which also yields exact energymomentum conservation laws through the Noether method. [Preview Abstract] 

NP10.00002: A Novel Theory of AC Contact Resistance Foivos Antoulinakis, Y. Y. Lau Electrical contact is an important issue to high power microwave sources, pulsed power systems, field emitters, thin film devices and integrated circuits, and interconnects, etc. Contact resistance, and the enhanced ohmic heating that results, have been treated mostly under steady state (DC) condition. In this paper, we consider the vastly more complex problem of AC contact resistance. We consider a simple geometry, namely, that of two semiinfinite slab conductors of different thicknesses and different electrical properties joint at z $=$ 0. In the DC case, this model was solved exactly by Zhang and Lau [1]. Here, we present an exact solution under AC condition. New features that accompany AC condition, such as the resistive skin effect, inductive, and capacitive effects, as well as radiation losses will be presented. Both metal and semiconductor contacts are considered. Scaling laws for the AC contact resistance as a function of frequency have been constructed for several cases. [Preview Abstract] 

NP10.00003: An Ellipsoidal LenardBernstein Kinetic Model for Plasmas William Sands, Jeffrey Haack We extend the LenardBernstein collision model, which is a linear FokkerPlanck collison model, to allow for anisotropy in the effective target distribution. Additionally, we incorporate MDverified cross sections in the definitions of the collision frequency and transport coefficients to provide the fidelity of a Boltzmann model in the hydrodynamic limit. We perform a consistent numerical comparison of this model with other collision operators used in kinetic modeling of plasmas. [Preview Abstract] 

NP10.00004: Collective and shielding effects on nuclear fusion reaction in nonideal plasmas MyoungJae Lee, YoungDae Jung The nuclear fusion reaction process is investigated in partially ionized nonideal plasmas. The effective pseudopotential model taking into account the collective and plasma shielding effects is applied to describe the interaction potential in nonideal plasmas. The analytic expressions of the Sommerfeld parameter, the fusion penetration factor, and the cross section for the nuclear fusion reaction in nonideal plasmas are obtained as functions of the nonideality parameter, Debye length, and relative kinetic energy. It is found that the Sommerfeld parameter is suppressed due to the influence of collective nonideal shielding. It is also found that the fusion penetration factors in nonideal plasmas represented by the pseudopotential model are always greater than those in ideal plasmas represented by the DebyeHückel model. In addition, it is shown that the collective nonideal shielding effect on the fusion penetration factor decreases with an increase of the kinetic energy. [Preview Abstract] 

NP10.00005: Nbody numerical simulation of particle transport in the presence of background magnetic field Yasutaro Nishimura Coulomb collisional process and Debye shielding is investigated in the presence of external magnetic field employing Nbody numerical simulation.\footnote{C.P.Wang and Y.Nishimura, IEEE Transactions on Plasma Science, 47, 1196 (2019).} Conventional Debye shielding can be prevented when the electron Larmor radius becomes comparable or smaller than the Debye length. Ambipolar diffusion, both in the parallel and the perpendicular direction is examined. [Preview Abstract] 

NP10.00006: Exact irreducible moments of the Landau collision operator in the randomvelocity moment expansion JeongYoung Ji, J. Andrew Spencer, Eric D. Held Exact moments of the Landau collision operator are calculated for the irreducible Hermite polynomials written in terms of the randomvelocity variable. We present closed, algebraic formulas that reproduce the results for the totalvelocity moment expansion\footnote{J.Y. Ji and E. D. Held, Phys. Plasmas {\bf 13}, 102103 (2006).} and for the randomvelocity moment expansion with the small massratio approximation\footnote{J.Y. Ji and E. D. Held, Phys. Plasmas {\bf 15}, 102101 (2008).}. The collisional moments can be applied in the derivations of Braginskii and integral closures for arbitrary relative flow velocity between electrons and ions. Modifications to Braginskii closures are discussed. [Preview Abstract] 

NP10.00007: Lagrangian vs.\ Dirac constraints for ideal incompressible fluids and magnetofluids P. J. Morrison, T. Andreussi, F. Pegoraro In his famous work [1], Lagrange used Lagrange multipliers in the Lagrangian variable description of the ideal barotropic fluid to impose the incompressibility constraint. In modern (although no more rigorous) terminology this is referred to as geodesic flow on the group of volume preserving diffeomorphisms. An alternative approach for enforcing constraints was introduced by Dirac, one that was adapted to the Eulerian variable description of the fluid by a generalization of Dirac's constraint method [2,3] using noncanonical Poisson brackets [4]. It will be shown how Lagrange's method is equivalent to geodesic flow and how it compares to Dirac's method in terms of canonical Poisson brackets. The pros and cons of the various methods will be discussed for both finite and infinitedimensional examples. In addition the definition and use of energy for stability will be described with application to magnetofluid dynamics. \\ [1] J. L. Lagrange, M\'ecanique Analytique (Paris, 1788). \\ [2] P. J. Morrison et al., Ann. Phys. 324, 1747 (2009). \\ [3] C. Chandre et al., Phys.~Lett. A 376, 737 (2012). \\ [4] P. J. Morrison, Rev. Mod. Phys. 70, 467 (1998). [Preview Abstract] 
(Author Not Attending)

NP10.00008: A general metriplectic framework and dissipative extended magnetohydrodynamics Baptiste Coquinot, P. J. Morrison General equations for conservative yet dissipative (entropy producing) extended magnetohydrodynamics (XMHD) are derived from twofluid theory. Keeping all terms generates unusual crosseffects, such as thermophoresis and a current viscosity that mixes with the usual velocity viscosity. While the Poisson bracket of the ideal version of this model have already been discovered, we determine its metriplectic counterpart that describes the dissipation. This is done using a new and general thermodynamic point of view for deriving dissipative brackets, a means of derivation that is natural for understanding and creating dissipative brackets. Finally the formalism is used to study dissipation in the Lagrangian variable picture where, in the context of XMHD, nonlocal dissipative brackets naturally emerge.\footnote{For preprint see arXiv:1906.08313 [physics.fludyn].} [Preview Abstract] 

NP10.00009: Transitions between Thermionic, Field, and Vacuum Space Charge Limited Emission. Caleb Darr, Adam Darr, Sarah Lang, Allen Garner Electron emission is critical in operation of high power microwave and directed energy devices, and as a mechanism for gas breakdown for atmospheric microplasmas. While previous studies have unified field emission (FE) with spacecharge limited emission (SCLE) [1], electrodes operate at nonzero temperature, motivating this study to derive a simple theory unifying SCLE, FE, and thermionic emission (TE). Specifically, we unify FE and TE, modeled by General Thermal Field (GTF) equation [2], with SCLE in vacuum, represented by the ChildLangmuir (CL) law. The asymptotic solutions for FE, CL, and TE intersect at a nexus point that is highly sensitive to initial conditions, analogous to previous results for FE with SCLE and collisions [1]. The nexus point is uniquely defined by the emitter temperature, gap distance, or voltage and acts a guidepost for identifying operating regimes. Temperatures above the nexus limit causes emission to transition from TE to FE to CL, while lower temperatures exhibit FE to CL. Ultimate extension to include collisions will be discussed. [1] A. M. Darr, A. M. Loveless, and A. L. Garner, Appl. Phys. Lett. 114, 014103 (2019). [2] K. L. Jensen, J. Appl. Phys. 102, 024911 (2007). [Preview Abstract] 

NP10.00010: Plasma simulations with a domainhybridized model I. A. M. Datta, A. Ho, U. Shumlak Highfidelity simulations of plasma dynamics are facilitated by an approach incorporating multiple mathematical descriptions that represent varying degrees of physical completeness. These include a single fluid magnetohydrodynamic (MHD) model, a multispecies (electrons, ions, and neutrals) 5moment fluid model, and a continuum kinetic plasma model. The WARPXM highorder finite element framework developed at the University of Washington implements these models using a discontinuous Galerkin spatial discretization on unstructured meshes with RungeKutta time integration. These models are also being synthesized in a domaindecomposed hybrid model, in which different models are applied in different regions of the simulation, based on local plasma properties including the degree of magnetization, charge separation, and collisionality. Various plasma problems are studied using this model, including that of magnetic reconnection and plasma sheaths. The goal of this work is to determine the parameter regimes most appropriate for each model to maintain sufficient physical fidelity over the whole domain while minimizing computational expense. [Preview Abstract] 

NP10.00011: Hybridizable Discontinuous Galerkin Numerical Methods and their Applicability to Plasma Simulation Codes Andrew Ho, Uri Shumlak, Iman Datta Hybridizable Discontinuous Galerkin (HDG) is a relatively new and novel approach for discretizing advectiondiffusionreaction problems. Key advantages of this method is that it is capable of obtaining optimal convergence rates, exhibits good numerical conditioning for implicit/algebraic solvers, and is amenable to a highly efficient generalization of static condensation for reducing the system size of the global implicit solve. The method has been demonstrated to be effective at handling a wide variety of traditional linear and nonlinear PDE problems, including the incompressible resistive MHD system. This research investigates the applicability of HDG methods for handling the 5Nmoment multifluid plasma model, mixed potential formulations for Maxwell's equations, and the effectiveness of coupling HDG with Additive RungeKutta (ARK) ImplicitExplicit (ImEx) temporal solvers for plasma systems. [Preview Abstract] 

NP10.00012: Geometric theory of Klimontovich representation and structurepreserving geometric particleincell algorithms Hong Qin, Alexander S. Glasser Structurepreserving geometric algorithms in plasma physics [1] numerically preserve the structures of physical systems, such as the local energymomentum conservation law, symplectic structure, and gauge symmetry, for arbitrarily large number of simulation timesteps. They possess longterm accuracy and fidelity and are especially suited for exascale hardwares. Their advantages over conventional algorithms have been amply demonstrated. A key component of the structurepreserving geometric particleincell algorithms [24] is the geometric theory of the Klimontovich representation, which geometrically discretizes the Poisson structure on the infinite dimensional dual of the Lie algebra of distribution densities as [3] \[ \int f\{\frac{\delta H}{\delta f},\frac{\delta G}{\delta f}\}_{xp}dxdp=\sum_{i=1}^{N}\left(\frac{\delta h}{\delta X_{i}}\frac{\delta g}{\delta P_{i}}\frac{\delta g}{\delta X_{i}}\frac{\delta h}{\delta P_{i}}\right). \] More fundamentally, the geometric theory of the Klimontovich representation establishes a symplectic structure for the VlasovMaxwell system from the first principles of physics. [1] Qin et al., PRL 100, 035006 (2008). [2] Squire et al., PoP 19, 084501 (2012). [3] Qin et al., Nucl. Fusion 56, 014001 (2016). [4] Xiao et al., PoP 22, 112504 (2015). [Preview Abstract] 

NP10.00013: On Charge Conservation in ParticleInCell Methods Alexander S Glasser, Hong Qin In recent years, much work has been devoted to exactlychargeconserving particleincell (PIC) methods that simulate the collective dynamics of particles and electromagnetic fields. While it is rightly observed that these methods' gauge symmetry gives rise to their charge conservation, this causal relationship has been loosely described in ad hoc derivations of the associated conservation laws. In the following work, we more firmly establish the causal relationship between PIC methods' gauge symmetry and charge conservation. In the formalism of Noether's Second Theorem, we demonstrate that gauge symmetry in Lagrangian variational PIC methods gives rise to local charge conservation as an offshell identity. We further examine Hamiltonian PIC methods, and discover sufficient conditions for the preservation of the momentum map in splitting schemes. We elucidate the status of local charge conservation laws in such splitting methods, and explore the improved preservation of structure in the covariant (i.e. multisymplectic) Hamiltonian formalism. [Preview Abstract] 
(Author Not Attending)

NP10.00014: Quantum Algorithms for Efficient Classical Plasma Simulation Alexander Engel, Graeme Smith, Scott Parker In the field of quantum computing, algorithms are being developed that offer a variety of speedups over their classical counterparts. Could future quantum computers be applied to reduce the costs of kinetic plasma simulations? We investigate this question by developing a quantum algorithm for a very simple plasma problem: linear Landau damping. This algorithm is designed to be run on a universal, errorcorrected quantum computer, and is worked out in detail and verified numerically. While classical simulation of the VlasovPoisson system has costs that scale as $\mathcal{O}(N T)$ for a phase space grid with $N$ grid points and simulation time $T$, our quantum algorithm scales as $\mathcal{O}(\text{polylog}(N) T/\delta)$ where $\delta$ is the measurement error. We find that a quantum computer could efficiently handle a high resolution, sixdimensional phasespace grid, but the $1/\delta$ cost factor to extract a result remains a difficulty. Since we only handle linear, damped cases, this is not a general algorithm for present day kinetic plasma simulation, but by working out the details we showcase the capabilities and limitations of quantum computers, generally and in the specific context of classical plasma physics simulation. [Preview Abstract] 

NP10.00015: GeFiE{\&}B:A New Particle Simulation Scheme using Electromagnetic Fields Liu Chen, Yu Lin, Xueiyi Wang, Jian Bao A gyrokinetic electron and fully kinetic ion (i.e., GeFi) particle simulation scheme, valid for fluctuations with wave frequency up to $\omega $ \textless \textless $\Omega_{\mathrm{e}}$ has been developed [\textit{Lin et al}., 2005, 2011]. Here, $\Omega_{\mathrm{e}}$ is the electron cyclotron frequency. Such scheme is applicable for simulating plasma dynamics in which the wave modes ranging from Alfven waves to lowerhybrid/whistler waves must be handled on an equal footing; e.g., the physics of collisionless magnetic reconnection with a finite guide field and lower hybrid/whistler mode waves in space and laboratory fusion plasmas., while employing the realistic iontoelectron mass ratio. In the gyrokinetic treatment, field equations are usually described by the scalar ($\delta \varphi )$ and vector ($\delta $A) potential variables. Poisson's equations are thus needed to solve for the electromagnetic fields and may present computational challenges for realistic nonuniform and multidimensional magnetic field geometries. Here, we present a new GeFi particle simulation scheme that employs the electric field \textbf{E} and magnetic field \textbf{B }directly as field variables and advances particles accordingly. Contrary to previous hybrid simulation models based on the field variables, the present scheme (GeFiE{\&}B) also treats the displacement current selfconsistently and, thus, includes spacecharge waves. A corresponding nonlinear gyrokinetic equation in terms of electromagnetic fields is also derived. For the case of linear waves in a uniform plasma, simulation results are successfully benchmarked against the analytically derived linear dispersion relations [Preview Abstract] 

NP10.00016: 3D Vortex Solitons in Hyperbolic SelfDefocusing Nonlinear Media using unitary qubit lattice algorithms suitable for quantum computing Linda Vahala, George Vahala, Min Soe, Abhay Ram The nonlinear Schrodinger equation (NLS)  a ubiquitous equation of nonlinear physics  models Langmuir waves in hot plasmas. A stable bright or a stable dark soliton/vortex arises from the swign on the nonlinear term. in 3D NLS there are no stable structures. Efremidis [1] found quasistationary vortices provided the standard elliptic operator is transformed to hyperbolic. Now the transverse dark soliton is stabilized by the longitudinal bright soliton. We present here a qubit unitary lattice algorithm, with 2 qubits for the scalar field at each lattice site. These two qubits are then locally entangled by unitary collision operators and then that entanglement is propagated throughout the lattice by unitary streaming operators. The resulting mesoscopic algorithm is ideally parallelized and can be readily encoded onto a quantum computer. It is seen that while there is a quasistable m $=$ 1 vortex, the m $=$ 2 vortex is unstable: from quantum vortex theory the energy of a m $=$ 2 quantum vortex is greater than twice that of an m $=$ 1 vortex. This leads to a rapid transition to two m $=$ 1 vortices. [1] N. K. Efremidis et. al. Phys. Rev. Lett. \textbf{98}, 113901 (2007) [2] L. Vahala et. al. Commun Nonlinear Sci Numer Simul \textbf{75}, 152159 (2019) [Preview Abstract] 

NP10.00017: Study of NonAbelian Quantum Turbulence using Qubit Unitary Lattice Simulations George Vahala, Linda Vahala, Min Soe In 3D classical incompressible turbulence, one obtains the k$^{\mathrm{5/3\thinspace }}$Kolmogorov energy cascade. In quantum turbulence one has vortex reconnection without viscosity. The topological properties of the order parameter manifold restrict the collision dynamics of vortexvortex interaction. For scalar quantum turbulence [1], with only Abelian vortices, a triple total energy cascade region is seen on a 5760$^{\mathrm{3}}$ grid, while the incompressible part of the energy shows a single cascade of k$^{\mathrm{3}}$. NonAbelian turbulence [2] requires 5 coupled NLS equations (c.f., spin2 BEC). We perform unitary qubit analysis for vortex reconnection of nonAbelian equivalence classes. Following these studies we are in a position to perform high resolution nonAbelian quantum turbulence simulations. Previous CFD studies [2] required the addition of numerically stabilizing dissipation and compensating energy influx. Our qubit unitary lattice algorithm requires no such numerical artifacts and is immediately transferable to a quantum computer. [1] J. Yepez, G. Vahala, L. Vahala and M. Soe, Phys Rev. Lett \textbf{103}, 084501 (2009) [2] M. Kobayashi et. al. Phys. Rev. Lett. \textbf{103}, 115301 (2009), arXiv 1606.07190 (2016) [Preview Abstract] 

NP10.00018: Initial Comparison of EMPIRE Simulations with Diodes Driven by the Photoelectric Effect Keith Cartwright, Christopher Moore, Kate Bell, Timothy Flanagan, Peggy Christenson, Matthew Bettencourt, Timothy Pointon, Elaine Raybourn, Nicholas Roberds EMPIRE is a new EM plasma simulation capability under development that includes kinetic (PIC) plasma representation and DSMC collisions. The EMPIRE code is designed to run on advanced hardware, e.g.\ ARM and GPGPUs, through a Kokkos abstraction layer to enable portability. For this initial comparison we will focus on testing the electromagnetic solve in enclosed cavities fielded at the Z Machine and the NIF. Powerful, pulsed xray sources available at these facilities (radiating terawatts in nanoseconds) drive plasmas in cavities due to xraysurface interactions. Prior to irradiation, cavity volumes have either background partial pressures of inert gas, or are at near vacuum $(<5\times10^{5}$Torr$)$. Upon irradiation, surface photoelectrons are modeled as well as effects due to extreme surface heating caused by xray energy deposition that drives thermionic emission and thermally enhanced neutral desorption. We will compare the results of these model to experiments. [Preview Abstract] 

NP10.00019: Hybrid fluidkinetic models for highenergydensity plasmas Sean Miller, Eric Cyr, Thomas Gardiner, Matthew Bettencourt, Nathaniel Hamlin, Kristian Beckwith, Sidney Shields Plasma physics in the highenergydensity regime can be dominated by collisional interactions between particles. Particleincell (PIC) based kinetic representations have classically been used to represent these systems in rarefied regimes, however as the density of the plasma increases  or a neutral gas is introduced  the computational costs of particle methods increase. The goal of this research is to develop hybrid representations where the addition of continuum fluid components to the particle solve reduces runtimes in dense plasma simulations while retaining physical accuracy in rarefied regimes. Two approaches will be presented: (1) a speciesbased coupling where each species is represented by a different discretization (e.g. PIC ions with fluid electrons/neutrals), and (2) a PIC discretization is used to close the fluid model  commonly known as a deltaf method. The current state of our implementation will be presented and the benefits and challenges of these approaches will be discussed. [Preview Abstract] 

NP10.00020: Variable HighOrder Shock Capturing with GPWENO in the FLASH Code Adam Reyes, Dongwook Lee, Carlo Graziani, Petros Tzeferacos We present an implementation of a shockcapturing scheme for hyperbolic equations. The method attains highorder of accuracy by using kernelbased Gaussian process (GP) data prediction for the reconstruction of Riemann states in a finite volume framework. To handle shocks and discontinuities the method adopts a strategy similar to the weighted essentially nonoscillatory (WENO) schemes. In GPWENO the GP prediction takes place of the polynomial interpolation and the conventional $L_2$ type WENO smoothness indicators are replaced with the Gaussian likelihood derived from the underlying GP model. The new GP smoothness indicators provide significant improvements in delivering a selectable highorder accuracy in smooth flows, while giving nonoscillatory solutions in discontinuous flows. We benchmark GPWENO on a suite of test problems using an implementation in the FLASH code. This addition promises a significant enhancement to the code’s fidelity in modeling laserdriven plasma experiments. [Preview Abstract] 

NP10.00021: Nonuniform Mesh Based hPIC Code for Efficient ScrapeOffLayer Computation Md Fazlul Huq, Vignesh VittalSrinivasaragavan, Onkar Sahni, Davide Curreli Uniform structured meshes are inefficient in capturing the high plasma gradients in a ScrapeOffLayer (SOL) spanning a large region including the magnetic and electrostatic sheaths forming in front of material surfaces. In order to resolve the large gradients across the plasma sheath region at a reduced computational cost, we have implemented an approach using a nonuniform mesh in the hPIC Particle In Cell code using the Parallel Unstructured Mesh Infrastructure (PUMI) library. The mesh nonuniformity requires to update not only the field solver, but also the PIC weighting and interpolation procedures in order to avoid artificial forces. On top of the nonuniformity, the algorithm allows to split the entire plasma region into a number of segments hierarchically, for local mesh grading and refinement. Currently, we employ up to 3 segments arranged in a logical order including a segment with a uniform mesh and two segments using boundarylayer meshes with mesh size following a geometric gradation biased at the left and right ends. We report performance measurements on the code, showing that, thanks to the new mesh, the code can resolve a region of ScrapeOffLayer much larger than with a corresponding uniform mesh. [Preview Abstract] 

NP10.00022: A New Numerical Scheme to enforce Charge Conservation in ParticleinCells with Boltzmann Electrons Moutaz Elias, Davide Curreli, James Myra ParticleInCell simulations of transient magnetized plasma sheaths including fully kinetic electrons and fully kinetic ions remain a big challenge due to the vast discrepancies in electron dynamics and ion transport timescales. Reduced electron models are typically necessary to bridge the time scale separation between the two species, the most employed being the MaxwellBoltzmann electron approximation. However, using Boltzmann electrons typically requires to enforce global charge conservation in order to avoid spurious electrostatic oscillations. This is particularly challenging in timedependent PIC simulations (like RF plasmas) or currentcarrying plasmas, where ad hoc assumptions are typically necessary (Hagelaar, 2007). Here, we present a new numerical scheme to enforce charge conservation in ParticleinCells using Boltzmann electrons. The scheme is local in time, and provides the reference Boltzmann electron density at each time step in a selfconsistent way. The scheme is applicable to both implicit and explicit ParticleInCell simulations using Boltzmann electrons. We report tests on magnetized RadioFrequency plasma sheath as an example. Comparisons with fluid codes (J.Myra, 2015) for the same problem are also reported. [Preview Abstract] 

NP10.00023: Efficient Electromagnetic Fourier Basis Particle Simulation Matthew Mitchell, Matthew Miecnikowski, Greg Beylkin, Scott Parker The standard particleincell algorithm suffers from grid heating and numerical instabilities. There exists a gridless alternative which bypasses the deposition step and calculates each Fourier mode of the charge and current densities directly from the particle positions. We show that a gridless method can be computed efficiently through the use of an Unequally Spaced Fast Fourier Transform (USFFT) algorithm. After a spectral field solve, the forces on the particles are calculated via the inverse USFFT (a rapid solution of an approximate linear system). We provide an implementation of this algorithm in one spatial and two velocity dimensions with an asymptotic runtime of $O(N_p + N_m^D \log N_m^D)$ for each iteration, identical to the standard PIC algorithm (where $N_p$ is the number of particles, $N_m$ is the number of Fourier modes, and $D$ is the spatial dimensionality of the problem). We demonstrate superior energy conservation and reduced noise, as well as convergence of the energy conservation at small time steps. [Preview Abstract] 

NP10.00024: Fourthorder VlasovPoisson simulations of kinetic instabilities and transport in lowbeta ExB environments G. V. Vogman, J. H. Hammer, W. A. Farmer Pulsed power experiments run megaamps of current through a load to produce and study high energy density plasmas. Current is delivered using magnetically insulated transmission lines, which feature an environment where the electric and magnetic fields are orthogonal. The formation of low density plasmas in these power feeds is known to degrade performance of experiments and to prevent scaling to higher currents. To understand the inimical transport properties of these lowbeta, collisionless, nonMaxwellian plasmas and how they affect experimental outcomes, the power feed environment is studied using conservative fourthorder finitevolume VlasovPoisson simulations in $(x,y,v_x,v_y)$ phase space. The computational study is facilitated by the development of robust methods for constructing customizable selfconsistent twospecies kinetic equilibria, in which spatial profiles are nonuniform and can feature Larmor radii that are comparable to gradient scale lengths. The ability to construct and accurately capture equilibria in noisefree timedependent simulations provides a powerful means of investigating isolated kinetic transport physics. The machinery is applied to study shearedflow instabilities in nonuniform plasmas with significant finite Larmor radius effects. [Preview Abstract] 

NP10.00025: Equation Free Projective Integration Enabled by Dynamic Mode Decomposition Sebastian De Pascuale, David Green We demonstrate the application of dynamic mode decomposition (DMD) on a classic multiscale problem in plasma physics: the ponderomotive modification of electron density by an oscillating electric field. DMD functions as a datadriven method that separates spatiotemporal scales simultaneously, an advantageous feature over limited Fourier and wavelet techniques. We leverage DMD in an automated procedure to identify and extract the slow secular drift of the ponderomotive force from 1x1v Vlasov simulations of the fast system response to an applied electric field. We reconstruct the time averaged effect on the fluid density moment from analysis of the fast kinetic distribution function. This reconstruction enables an equation free projective integration (PI) of the quantity, where the form of the ponderomotive force is treated as unknown but its resultant effect is approximated by decomposition of simulation data into dynamic modes. Each spatial mode has a corresponding temporal variation that can projected outside of the sampling set. We devise a parameterization of the DMD method into a mapping between slow and fast scales in the equation free paradigm. We show improved accuracy over naive explicit Euler PI and discuss progress on a Picard iteration based PI. [Preview Abstract] 

NP10.00026: Determining where collisions and nonlinearity are significant using the Gtransform J. M. Heninger, P. J. Morrison The effects of collisions and nonlinearity are often localized in phase space. We present a technique to determine where collisions and nonlinearity have been most significant. The Gtransform, an integral transform based on the Hilbert transform, converts the linearized equations of motion for the distribution function into a simple advection equation. We apply the Gtransform to the distribution function at any time, undo the linear behavior (including Landau damping) using the solution to the advection equation, and then transform back. Comparing this quantity to the initial conditions for the distribution function shows where in phase space the collisions and nonlinearity have modified the distribution function. [Preview Abstract] 

NP10.00027: The PlasmaPy Project: Toward an Open Source Software Ecosystem for Plasma Physics Nicholas A. Murphy, Dominik Sta\'nczak, Pawel M. Kozlowski, Andrew J. Leonard, Ritiek Malhotra, Samuel Langendorf, Jasper Beckers, Erik Everson, Tulasi N. Parashar, David Stansby, Stuart Mumford, David Schaffner PlasmaPy is a communitydeveloped open source core Python package for plasma physics in the early stages of development. This package is being developed to provide the core functionality that is needed to support a fully open source Python ecosystem for plasma physics. PlasmaPy prioritizes code readability, consistency, and maintainability while using best practices for scientific computing such as version control, continuous integration testing, and code review. PlasmaPy has a code of conduct and is available under a BSD 3clause license with explicit protections against software patents. We will describe the capabilities in PlasmaPy’s version 0.2.0 release and PlasmaPy’s development roadmap. We will discuss how members of the plasma physics community can become contributors to this project. [Preview Abstract] 

NP10.00028: Adaptive Sparse Grids for Fusion Relevant High Dimensional PDEs. David Green, Lin Mu, Ed D'Azevedo, Tyler McDaniel, Wael Elwasif, Graham Lopez, Timothy Younkin, Adam McDaniel Predicting the behavior of magnetic confinement fusion devices requires the solution of high dimensional PDEs. Traditional grid or meshbased methods for solving such systems in a noisefree manner quickly become intractable due to the scaling of the degrees of freedom going as O(N\textasciicircum d), sometimes called "the curse of dimensionality." We are developing an arbitrarily highorder discontinuousGalerkin finiteelement solver that leverages the sparsegrid discretization whose degrees of freedom scale as O(N*log2N\textasciicircum D1). In this paper, we employ the adaptive aspect of our solver in a study of how adaptivity in the selection rule for truncating the tensor products affects the advantages of sparsegrids for fusion relevant problems. [Preview Abstract] 

NP10.00029: 2D axialazimuthal ParticleInCell benchmark for lowtemperature partially magnetized plasmas T. Charoy, J.P. Boeuf, A. Bourdon, J.A. Carlsson, P. Chabert, B. Cuenot, D. Eremin, L. Garrigues, K. Hara, I.D. Kaganovich, A.T. Powis, A. Smolyakov, D. Sydorenko, A. Tavant, O. O. Vermorel, W. Villafana Representative simulation case to study lowtemperature partiallymagnetized plasmas is defined. Seven independently developed ParticleInCell codes have simulated this benchmark case, with the same specified conditions. The characteristics of the codes used, implementation details or computing times and resources, are given. We compare the steadystate the timeaveraged axial profiles of 3 main discharge parameters (axial electric field, ion density and electron temperature). We show that the results obtained exhibit a very good agreement within 5{\%} between all the codes. An analysis of the instabilities propagating in the direction of electron drift is performed and a similar behaviour is retrieved between all the codes. A particular attention has been paid to the numerical convergence by varying the number of particles per cell; it is shown that this benchmark case displays a good convergence. [Preview Abstract] 

NP10.00030: Modeling plasma fluidtokinetic transitions with speedlimited PIC methods in VSim Thomas Jenkins, G. R. Werner, J. R. Cary, A. M. Chap, P. H. Stoltz, D. N. Smithe Speedlimited particleincell (SLPIC) modeling [G. R. Werner et al., Phys. Plasmas 25, 123512 (2018)], has been shown to model plasmas characterized by lowvelocity kinetic processes significantly faster than conventional PIC methods. SLPIC, like PIC, retains a fully kinetic description of the plasma, but also imposes an artificial speed limit on fast particles whose kinetics do not play a meaningful role in the system dynamics. Larger simulation timesteps, which enable faster simulations of such discharges, are thus permitted. SLPIC has been implemented in the VSim code [C. Nieter and J. R. Cary, J. Comp. Phys. 196, 448 (2004)]. In this poster we'll show how SLPIC can be used to rapidly model the evolution of a plasma discharge through transient or fluidlike phases, and can then continuously transition to a conventional PIC model with smaller timesteps as kinetic processes in the discharge become important. Applications include plasma opening switches (fluidlike in the conduction phase, but kinetic in the opening phase) and magnetron sputtering configurations (wherein convergence to steadystate is slow due to collisional effects between species with large mass ratios). VSim simulations of these and other SLPICrelevant discharges will be presented. [Preview Abstract] 

NP10.00031: WICKED: A Computational Framework for the Evolution of Wave Turbulence in Inhomogeneous Plasmas Chris Crabtree, Gurudas Ganguli, Alex Fletcher, Steve Richardson Kinetic effects can impact the evolution of global scale systems and yet often firstprinciples kinetic simulations are not feasible. Some canonical examples, include (1) the evolution of VLF waves in the radiation belts along with energetic electrons, and (2) the evolution of lowerhybrid turbulence by injection of heavy ions. Wave turbulence theory offers a reduced description of the evolution that may be more efficient. It consists of a diffusion equation describing the evolution of the action variables for resonant particles, i.e. a quasilinear equation, and a wavekinetic equation that describes the transport of waveenergy along rays defined by a dispersion relation. The waves grow or damp due to linear interactions with the particles which through conservation of energy and momentum causes diffusion of particle action. The waves may also scatter due to nonlinear interactions. By treating both particles and waves as computational particles we develop a numerical solution to the coupled equations that we call WaveinCell. We present ongoing efforts to develop a computational framework (WICKED: WaveInCell for Kinetic Energetic Dynamics) to solve these equations in inhomogeneous plasmas and compare the results to PIC simulations. [Preview Abstract] 

NP10.00032: Achieving Optimal VPIC Performance on Several Modern CPU Architectures William Nystrom, Douglas Jacobsen Two significant modifications to the VPIC \footnote{K. J. Bowers, B. J. Albright, L. Yin, B. Bergen, and T. J. T. Kwan, Phys. Plasmas 15, 055703 (2008)} particle advance implementation are being explored. The first is the use of an Array of Structs of Arrays (AoSoA) data structure for the particles which eliminates the need to transpose vector loads of particle data after loading into vector registers and before storing back to memory. The second is the use of a particle sort performed for every timestep which allows particles to be processed as a double loop over cells and the particles in each cell. This second modification allows several optimizations including hoisting the load of interpolation data and the store of current density accumulation data out of the percell particle loop. These modifications eliminate a performance bottleneck associated with shuffle and permute operations in data transpose operations and increase the efficiency of VPIC's use of available memory bandwidth. Initial performance results for some of the VPIC particle kernels is greater than 2x. Results for the complete implementation will be presented on several modern architectures including Intel Knights Landing and IBM Power 9. [Preview Abstract] 

NP10.00033: An implicit, higherorder, electromagnetic Vlasov solver Alexander Stamm, Frank Lee, Bradley Shadwick The development of an electromagnetic Vlasov solver in the 1.5 dimensional coordinate system (1 spatial, 2 velocity coordinates) will be discussed. A comparison of 2nd and 4th order temporal methods will be shown, and extension to higher order phase space discretizations will be discussed. The Weibel instability will be used for comparison to an analytical van Kampen solution to the linear theory as well as to macroparticle methods. This comparison will provide the means of understanding the role of conservation behavior (charge, momentum, and energy) for a given computational efficiency. [Preview Abstract] 

NP10.00034: Progress on the Vorpal exascale transition Benjamin Cowan, Sergey Averkin, John Cary, Jarrod Leddy, Scott Sides, Ilya Zilberter Vorpal was designed nearly 20 years ago, with its first applications roughly four years later, as a highly performant, flexible plasma simulation code. Using object oriented methods, Vorpal was designed to allow runtime selection from multiple field solvers, particle dynamics, and reactions. It has been successful in modeling for many areas of plasma physics as well as RF and dielectric structures. Now it is critical to move to exascale systems, with their compute accelerator architectures, massive threading, and advanced instruction sets. Previous revolutionary changes, such as the move to distributed memory computing (MPI), led to entirely new applications, as the extensive required restructuring made new application development from scratch the more efficient process. Here we discuss how we have moved this complex, multiphysics computational application to the new computing paradigm, and how it was done in a way that kept the application producing physics during the move. We present performance results showing significant speedups in all parts of the PIC loop, including field updates, particle pushes, and reactions. [Preview Abstract] 

NP10.00035: EEDF effect on the plasma hysteresis: Theory, Experiment, and Modeling in RF inductive plasmas HyoChang Lee Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bistability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and nonRamsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EEDeffect can be regarded as a universal phenomenon in plasma physics. [1] H Lee and C Chung, Sci. Rep. 5, 15254 (2015), [2] H Lee, Appl. Phys. Rev. 5, 011108 (2018). [Preview Abstract] 

NP10.00036: Magnetic nulls in interacting dipolar fields Todd Elder, Allen Boozer Magnetic nulls make the behavior of field lines subtle even for simple curlfree magnetic fields. This behavior must be understood before magnetic reconnection can be. We examine nulls through the interaction of two magnetic dipoles embedded in perfectly conducting hollow spheres, one with a much stronger dipole moment than the other. The dipole moments are oriented at an arbitrary angle. Two magnetic nulls arise generically about the weaker dipole. Field lines near the nulls are of four topological types: lines that leave and enter the sphere of the weaker dipole, lines that either leave or enter the weaker dipole, and lines that never strike the weaker dipole. The relation of the properties near each point null, which involves spines and fans, and the global topological properties are determined. [Preview Abstract] 

NP10.00037: A new MHD/kinetic model for exploring particle acceleration in macroscale systems James Drake, Harry Arnold, Marc Swisdak, Joel Dahlin A novel MHD/kinetic model, kglobal, is being developed to explore magnetic reconnection and particle energization in macroscale astrophysical systems. The model blends the MHD with a macroparticle description. The rationale for this model is based on the discovery that energetic particle production during magnetic reconnection is controlled by Fermi reflection rather than parallel electric fields. Since the Fermi mechanism is not dependent on kinetic scales, the model is sufficient for describing particle acceleration in macrosystems. The kglobal model includes macroparticles laid out on an MHD grid that are evolved with the MHD fields. The feedback of the energetic component on the MHD fluid is included in the dynamics so total energy is conserved. The system has no kinetic scales and therefore can be implemented to model energetic particle production in macrosystems. It has been upgraded to include the macroscale parallel electric field required to describe return currents that develop in open systems. The new model has been benchmarked by studying the propagation of Alfv\'en waves and the growth of firehose modes in a system with anisotropic electron pressure. The first results on the exploration electron acceleration during reconnection will be presented. [Preview Abstract] 

NP10.00038: Scalings Pertaining to Current Sheet Disruption Mediated by the Plasmoid Instability YiMin Huang, Luca Comisso, Amitava Bhattacharjee Analytic scaling relations are derived for a phenomenological model [1] of the plasmoid instability in an evolving current sheet, including the effects of reconnection outflow. Two scenarios are considered: the plasmoid instability can be triggered either by an injected initial perturbation or by the natural noise of the system, where the latter represents the lowest level of fluctuations in the system. The leading order approximation for the current sheet width at disruption takes the form of a powerlaw multiplied by a logarithmic factor, and from that, the scaling relations for the wavenumber and the linear growth rate of the dominant mode are obtained. When the effects of the outflow are neglected, the scaling relations agree, up to the leading order approximation, with previously derived scaling relations based on a principle of least time.[2] The analytic scaling relations are verified with numerical solutions of the model. [1] Huang, Y.M., Comisso, L., and Bhattacharjee, A., Astrophys. J. 849, 75 (2017) [2] Comisso, L., Lingam, M., Huang, Y.M., and Bhattacharjee, A., Phys. Plasmas 23, 100702 (2016). [Preview Abstract] 

NP10.00039: Turbulent Reconnection in Collisionless Mesoscale Layers William Daughton, Adam Stanier, Ari Le A great deal of progress has been made towards understanding the physics of collisionless reconnection in kineticscale current sheets. Hightime resolution spacecraft observations in the Earth’s magnetosphere are in good agreement with fully kinetic simulations. Metaphorically, these kinetic layers are the {\em hydrogen atom} of reconnection physics, and at this scale our understanding is approaching maturity. However, the applicability to much larger systems remains highly uncertain. For example, the scale of a solar flare is 10 orders of magnitude larger than the electron inertial length, at which the frozenflux condition is normally broken. Kinetic simulations suggest that large 3D reconnection layers may fragment into a turbulent spectrum of interacting flux ropes, leading to a vast number of kineticscale reconnection sites. Such simulations are typically initialized with a highly extended kineticscale current sheet, which is not physically realistic, and precludes the possibility of reconnection occurring in much thicker layers. In this work, we present a new approach for driving turbulent reconnection in layers much thicker than the inertial scale, and we characterize the dynamics in these regimes. [Preview Abstract] 

NP10.00040: Nonlinear 3D kinetic modeling of the internal kink instability Adam Stanier, William Daughton, Andrei Simakov, Ari Le, Luis Chacon Fluxropes are ubiquitous in magnetized plasmas and often undergo kink instabilities. The macroscopic kink motion can generate a helical current sheet where magnetic fieldlines reconnect. Kink instabilities are typically studied with magnetohydrodynamic (MHD) models, but the validity of these models can break down in weakly collisional space and laboratory plasmas. Questions remain concerning the coupling between the macroscale MHD drive and the detailed kinetic physics of the reconnection layer in these regimes. Here we present a 3D nonlinear kinetic simulation of the m=1 internal kink instability in a straight tokamak. The helical current layer forms with macroscopic length and electronscale thickness before breaking up via the collisionless plasmoid instability. Secondary fluxropes generate stochastic magnetic field regions around the Xpoint and the m=1 island, and we track significant electron mixing in these regions. Due to strong macroscopic drive and weak magnetic shear, a 'quasiinterchange'like bubble propagates to the plasma core where it deforms the m=1 island and leads to turbulence in a significant volume of the plasma column. We compare these results with 2D (helical) and 3D MHD simulations. [Preview Abstract] 

NP10.00041: Detailed analyses of plasma heating during turbulent kinetic magnetic reconnection Ryusuke Numata, Nuno Loureiro In weakly collisional plasmas, heating of ions and electrons occurs due to phase mixing whereby creating small scale structures in velocity space, even if collisions are rare. It has been demonstrated that the heating via phase mixing is effective during magnetic reconnection [1]. We have shown that ions can be heated with the rate being similar to that of electrons in highbeta plasmas. In the presence of turbulence, magnetic reconnection and associated heating of plasmas may be altered. To study the effects of turbulence on magnetic reconnection, we perform turbulent kinetic magnetic reconnection simulations using the gyrokinetic model. In the previous preliminary study, we observe that, by injecting turbulence from large scale, initially the ion dissipation develops, then the electron dissipation follows to make the heating ratio remain similar to that without turbulence. In this presentation, we discuss how the heating of each species is enhanced by turbulence, and how it depends on plasma parameters, such as the plasma beta. [1] R. Numata and N. F. Loureiro, J. Plasma Phys. 81, 305810201 (2015). [Preview Abstract] 

NP10.00042: Small Scale Magnetic Reconnection in Kinetic Plasma Turbulence Vadim Roytershteyn, Stanislav Boldyrev, Gian Luca Delzanno Magnetic reconnection in turbulent plasmas has been steadily getting recognition as an important process that contributes to energy dissipation and may play a significant role in terminating nonlinear cascade of turbulent fluctuations. Furthermore, significant interest has arisen, in light of recent MMS observations, in magnetic reconnection at the smallest electron kinetic scales in turbulence. At such scales, ions are decoupled from magnetic field and do not appear to participate in the reconnection process. We present results of 3D fully kinetic simulations of decaying turbulence aimed at uncovering properties of such reconnection events, in particular under conditions corresponding to the Earth’s magnetosheath. The simulations are conducted using highly accurate spectral simulation tool SPS to allow careful characterization of small scale reconnection events, with particular attention paid to characterizing 3D structure of the reconnection regions. The simulations results are put in to context of theoretical developments targeting socalled inertial kinetic Alfven regime, characterized by small values of electron beta and ion beta of order one. [Preview Abstract] 

NP10.00043: Simulations of instabilities in the symmetric reconnection layer with a moderate guide field Jonathan Ng, LiJen Chen, Ari Le, Adam Stanier, Shan Wang, Naoki Bessho Recent Magnetospheric Multiscale (MMS) observations have revealed the importance of the nonlinear evolution of waves in the lowerhybrid frequency range during magnetotail reconnection, in a manner different from what is typically expected of the lowerhybrid drift instability in thin current sheets. We perform 2 and 3D kinetic simulations of reconnection in the moderate guide field regime in order to study the excitation of these waves and how they affect the reconnection dynamics close to the xline and in the exhaust. In particular, the role of the waves in demagnetizing electrons and causing agyrotropic electron distribution functions will be explored. [Preview Abstract] 

NP10.00044: Reconnection and high energy radiation in the outer magnetospheres of gammaray emitting pulsars Hayk Hakobyan, Alexander Philippov, Anatoly Spitkovsky Gammaray pulsars are thought to produce high energy photons in the outer magnetosphere close to the light cylinder via synchrotron radiation from nonthermal particles sustained in the current sheet. Magnetic reconnection near the Ypoint is an efficient mechanism for tapping the magnetic field energy and accelerating particles that can later radiate synchrotron photons. The presence of a substantial density of high energy photons close to the current sheet can make twophoton pair production an efficient source of additional plasma loading in the outer magnetosphere. We present the results of particleincell simulations of relativistic magnetic reconnection with selfconsistent pair production. Radiation from accelerated particles in the current sheet produces secondary pairs in which are advected into the current sheet where they are reaccelerated and produce more photons. We study how the inflow of the secondary plasma, with multiplicities up to a several hundred, reduces the effective magnetization of the current sheet, suppressing the acceleration in the sheet and driving the system to a selfregulated regime. Our results offer an explanation for the weak dependence observed by Fermi Observatory of the gammaray cutoff in pulsars on the magnetic field at the light cylinder. [Preview Abstract] 

NP10.00045: Properties of Turbulence and the Associated Particle Transport and Energization in LowBeta Reconnection Hui Li, Liping Yang, Xiaocan Li, Fan Guo We present analysis of 3D MHD and kinetic simulations of 3D reconnection in low$\beta$ plasmas, emphasizing the development and evolution of turbulence. We examine the properties of turbulence as well as its impact on particle transport and energization. We discuss the differences between 2D and 3D. Implications for astrophysical observations will be discussed as well. [Preview Abstract] 

NP10.00046: ~Acceleration due to motional electric field in magnetic reconnection Patrick Kilian, Fan Guo, Xiaocan Li, Hui Li In astrophysics magnetic fields can contain a large fraction of the overall energy budget of a system. When kinetic, nonideal fields change the topology through reconnection this energy can be converted to plasma heating, kinetic energy in bulk flows and the production of nonthermal, highly energetic particles. We performed selfconsistent kinetic simulations using VPIC to study particle acceleration in pair plasmas and find that the dominant mechanism of particle acceleration is not the localized nonideal electric field at the reconnection site, but rather the ideal electric field induced by the plasma motion. This has implications for the particle spectrum and maximum attainable energy in astrophysical systems such as pulsar wind nebulae that are much larger than anything that can be simulated by kinetic simulations. ~ [Preview Abstract] 

NP10.00047: Energy Transfer through plasmoid reconnection in slabgeometry resistive MHD computations Jacob Maddox, Carl Sovinec Magnetic reconnection can convert magnetic energy into thermal energy on timescales that are short relative to global resistive diffusion. While fast reconnection occurs on microscopic scales, it has significant implications for evolution on macroscopic scales. We present 2D resistive MHD computations that, for some conditions, evolve from global resistive evolution through linear tearing and island formation, to currentsheet formation, rapid plasmoid reconnection and back to resistive evolution, depending on the tearing stability and dissipation parameters. Conditions that develop fast, plasmoidmediated reconnection transfer heat the plasma much faster than global resistive decay. The phase with fast plasmoid reconnection is characterized by high frequency creation and destruction of a variable number of plasmoid structures. We gather statistical information about the distribution of plasmoids formed and destroyed during the fast reconnection and link this distribution with the transfer of energy. The computations include viscous and resistive heating, without external sources or sinks, and the boundary conditions prevent a flux of energy into or out of the system; therefore, total system energy should be conserved. Hyperresistive effects can arise due to microscale plasma fluctuations. Here,~hyperresistivity in our computations prevents current sheets from collapsing to the numerical resolution scale during plasmoid growth. [Preview Abstract] 

NP10.00048: Anomalous Velocity Distributions Formed by PickUpLike Protons in Magnetic Reconnection Shunsuke Usami, Ritoku Horiuchi, Hiroaki Ohtani By means of particle simulations, we investigate ion dynamics responsible for heating during magnetic reconnection in the presence of a guide field. Experiments have reported that ions are heated mainly in the downstream of reconnection, but the mechanism remained unsolved. In Ref. [1], our particle simulations have demonstrated that ringshaped proton velocity distributions are formed, and protons are effectively heated during magnetic reconnection with a guide field. The proton behaviors are the PickUpLike. Upon entering the downstream across the separatrix, protons behave as nonadiabatic and are energized in the downstream. Recently, our simulations show anomalous shapes of velocity distributions, such as not only a simple ringshape, but also a hornshape [2], a circulararcshape, and further a multistructureshape combing them. We construct a theory accounting for the anomalous structures seen in velocity space. In our presentation, simulation results and the theory will be presented. [1] S. Usami, R. Horiuchi, and H. Ohtani, Phys. Plasmas 24, 092101 (2017). [2] S. Usami, R. Horiuchi, and H. Ohtani, Plasma Fusion Res. in press. [Preview Abstract] 

NP10.00049: Crossdiscipline study of the dynamics and energetics of the magnetic reconnection both in laboratory and space plasmas Masaaki Yamada, Hantao Ji, Mike Paluszek, Yevgeny Raitses, Jacob Simmonds, Jongsoo Yoo Despite enormous differences in the size of the reconnection layer (by $10^6$), remarkably selfsimilar characteristics have been observed in both laboratory and magnetosphere plasmas. The key dynamics were comparatively studied with data from laboratory (MRX) and space (MMS) in the context of twofluid physics, aided by numerical simulations [1]. A large potential well is observed within the reconnection plane with ions accelerated by the E field toward the exhaust. It was also found in MRX and numerical simulations that a half of inflow magnetic energy is converted to ions and electrons in the reconnection layer. While this measurement is yet to be verified in the magnetosphere, a concept of a supercluster cubesat system has been proposed, which is based on a 2D ($11\times11$) or 3D (${5\times5\times5}$) satellite grid in Earth’s magnetosphere [2]. With the key twofluid physics occurring in the scale length of 1200 km, optimal distance between adjacent satellites for measuring the structure of reconnection layer is 250 km, such that the total grid size can be 20500 km. This system should directly contribute to the understanding the global dynamics. Overall program scope will be presented. [1] M. Yamada, et al, Nature Comms, (2018) [2] M. Yamada, et al, “Proc. COSPAR (2017) [Preview Abstract] 

NP10.00050: Experimental study of the electron diffusion region during guide field magnetic reconnection Sayak Bose, H. Ji, W. Fox, M. Yamada, J. Yoo, J. JaraAlmonte, F. Pucci, A. Goodman The thickness of neutral current sheet in guide field reconnection has been measured under various geometries. However, the variation of the thickness of the electron diffusion region in the current sheet versus guide field strength is an open experimental question. In recent experiments, Fox et. al. [Phys. Rev. Lett. 118, 125002 (2017)] observed the electron diffusion layer to be wider than typical theoretical predictions [M. Hesse, Phys. Plasmas 13, 122107, (2006)], measured at a normalized guide field $B_{g}/ B_{rec}=$ 0.7,where $B_{rec\thinspace }$represents the upstream reconnecting component. We have studied the variation of the width of the electron diffusion region versus the guide field strength by varying guide field from 0 to 2 $B_{rec}$, in collisionless, two fluid regime in MRX. We have attempted to relate our results to data from other experiments like TS3/4,~and space observations under various geometries. [Preview Abstract] 

NP10.00051: Ion Doppler Tomography to Probe Ion Heating in the Presence of a Guide Field on the Magnetic Reconnection Experiment (MRX) Aaron Goodman, Hantao Ji, Jongsoo Yoo, Jonathan JaraAlmonte Magnetic reconnection is a fundamental plasma process in which magnetic energy is converted to particle energy during a global change in magnetic topology. Most reconnection events in space and fusion plasmas occur in the presence of a finite magnetic field, perpendicular to the reconnection layer, known as a guide field. Important questions in magnetic reconnection studies include how dissipated magnetic energy is distributed in the plasma and the mechanisms by which this energy is converted from field energy to particle energy. Computational studies and space data have begun to address the question of ion heating and energization in guide field configurations, however to date, only limited studies have been possible in laboratory plasmas. This is, in large part, due to diagnostic limitations. A new, lowtemperature, tomographic ion doppler diagnostic, designed for the Facility for Laboratory Reconnection Experiments (FLARE), and in use on the Magnetic Reconnection Experiment (MRX), is presented here. This diagnostic is optimized for FLARE but designed to function on both experiments and is used to obtain toroidal velocity and temperature from measurements of plasma emission. Initial data from multiple regimes of guide field reconnection, for both ions and neutrals are included. Details of the tomographic inversion are also presented. [Preview Abstract] 

NP10.00052: Stability Properties and Relaxation of Arched, LineTied Flux Ropes Andrew Alt, Clayton Myers, Hantao Ji, Jonathan JaraAlmonte, Jongsoo Yoo, Masaaki Yamada Coronal mass ejections occur when longlived magnetic flux ropes (MFR) anchored to the solar surface destabilize and erupt away from the Sun. These eruptions are driven in part by ideal MHD instabilities such as the kink and torus instabilities. These instabilities have long been considered in axisymmetric fusion devices where their instability criteria are given in terms of the edge safety factor and confining magnetic field decay index respectively. Previous laboratory experiments performed on the Magnetic Reconnection Experiment (MRX) revealed a class of MFRs that were torusunstable but kinkstable, which failed to erupt. These ``failedtori" went through a process similar to Taylor relaxation before their eruption ultimately failed. In more recent experiments we have investigated this behavior through additional diagnostics that allow us to measure the magnetic field in a 2D crosssection of the MFR along with limited outofplane measurements. These outofplane measurements allow for better measurement of the magnetic forces within an MFR. Understanding of the dynamic forces gives insight into the mechanisms behind eruptions and failed eruptions. The magnetic selforganization has also been investigated by measuring the redistribution of toroidal current within the MFRs. [Preview Abstract] 

NP10.00053: Particle Acceleration in Magnetic Reconnection Using LaserPowered Capacitor Coils Abraham Chien, Lan Gao, Hantao Ji, Brian Kraus, Kenneth Hill, Philip Efthimion, Gennady Fiksel, Eric Blackman, Philip Nilson, Kai Huang, Quanming Lu Magnetic reconnection is a ubiquitous astrophysical phenomenon at low plasma beta that rapidly converts magnetic energy into some combination of flow energy, thermal energy, and nonthermal energetic particles. The latter is often an observational signature of magnetic reconnection environments, which can be more efficient accelerators than competing processes such as isolated collisionless shocks. Experimental diagnostics have long limited most reconnection experiments to focus on the generation of plasma flow or thermal energy, leaving the acceleration of nonthermal particles unknown. To overcome this limitation, we have developed a robust platform for generating and measuring nonthermal energetic electrons from magnetically driven, quasiaxisymmetric reconnection using laserpowered capacitor coils and demonstrated this setup on the OMEGA EP laser facility at the Laboratory for Laser Energetics. Analysis of experimental proton radiographs shows consistency with expected reconnection fields. Further analysis with 2D particleincell reconnection simulations using realistic experimental conditions demonstrates good agreement with experiment in both reconnection electromagnetic fields and the resulting particle acceleration. [Preview Abstract] 

NP10.00054: Statistical properties of magnetic structures during turbulent reconnection in the Earth’s magnetotail Kendra Bergstedt, Hantao Ji, Matthew Chen A current area of interest in plasma physics is the formation of plasmoids in reconnecting current sheets and the effect that these structures have on the reconnection process. We present a statistical survey of a set of magnetic structures observed by the Magnetospheric Multiscale (MMS) mission during a period of turbulent magnetotail reconnection. The dissipation and electron energization from this dataset were previously studied (Ergun et al. 2018). The magnetic structures have a bipolar magnetic signature in the Z direction in geocentric solar magnetospheric (GSM) coordinates and most have sizes on the order of the electron or ion inertial length. The structures are categorized as topologically Xlike or Olike based on the type of bipolar signature and the directions of the electric currents and plasma flows within the structure. Distributions of their sizes and other properties are presented and fitted to empirical models. Evidence of merging plasmoids is presented, highlighting a possible mechanism of plasmoid growth. Implications of the reported results on our current understanding of turbulent reconnection mediated by plasmoids are discussed. [Preview Abstract] 

NP10.00055: FLARE: a collaborative user facility to study magnetic reconnection and related phenomena H. Ji, R. Bell, S. Bentivegna, A. Bhattacharjee, A. Carpe, D. Corl, A. Diallo, P. Efthimion, W. Fox, C. Gentile, A. Goodman, L. Hill, F. Hoffmann, J. JaraAlmonte, M. Kalish, T. Kozub, B. LeBlanc, M. Podesta, S. Prager, Y. Ren, P. Sloboda, M. Yamada, J. Yoo, W. Daughton, A. Stanier The FLARE device (Facility for LAboratory Reconnection Experiments; flare.pppl.gov) is a new experiment constructed at Princeton University for the study of magnetic reconnection in the multiple Xline regimes, directly relevant to space, solar, astrophysical, and fusion plasmas. The first plasma operation was successfully conducted to validate the engineering design and to demonstrate access to parameter space beyond its predecessor, MRX. Currently, the device is being relocated to PPPL while the power supplies are being upgraded to access new multiple Xline regimes in the reconnection phase diagram. A progress update including available diagnostics and the operation plan as a DoE collaborative user facility will be presented. [Preview Abstract] 

NP10.00056: New Milestones in Comparing Experimental and Simulated Reconnection: Results from TREX and Cylindrical VPIC Samuel Greess, Jan Egedal, Adam Stanier, Joe Olson, Bill Daughton, Ari Le, Alex MilletAyala, Rachel Myers, John Wallace, Mike Clark, Cary Forest Magnetic reconnection is studied in the Terrestrial Reconnection Experiment (TREX) under collisionless conditions relevant to the Earth's magnetosphere [1]. The thickness of the reconnection current layer normalized to electron kinetic length scales is one of the features most commonly used to identify different sets of reconnection dynamics. Previous studies suggest that experimental layer widths are larger by a factor of four compared to those in kinetic simulations [2]. However, results from TREX closely match the current width scaling and geometry seen in both prior 2D laminar kinetic reconnection simulations and new 3D VPIC models that have been developed specifically to reflect the TREX geometry. These findings will be presented along with results of the newest TREX run, with an adjustable guide field and a pressure anisotropy probe, and the associated VPIC simulation outputs. 1. Olson, J. et al. Experimental Demonstration of the Collisionless Plasmoid Instability below the Ion Kinetic Scale during Magnetic Reconnection. Phys. Rev. Lett. (2016). 2. Ji, H. et al. New insights into dissipation in the electron layer during magnetic reconnection. Geophys. Res. Lett. 35, L13106 (2008). [Preview Abstract] 

NP10.00057: How Alfv\'{e}n waves set the large scale structure of magnetic reconnection. Harsha Gurram, Jan Egedal, Willilam Daughton Kinetic Alfv\'{e}n waves (KAWs) have been postulated as a possible source of energy for the aurora[1]. Past studies have shown that they propagate superAlfv\'{e}nically for distances $\sim10R_e$ without significant damping [2]. However, from our study of Hall field profiles i.e $B_y(x,t)$ and $B_y(\psi,t)$ obtained from PIC simulation with domain $200d_i \times 30d_i$ and open boundary conditions, we observe that the large scale structure is carried by waves which are superAlfv\'{e}nic ($\sim 2V_{a}$) near the Xline where they are generated, as they travel into the exhaust for $\sim5R_e$ their propagation velocity decreases and become Alfv\'{e}nic ($~\sim 1V_{a}$). In the profiles of $B_y(x,t)$ we observe multiple $B_y$ structures in addition to the peak Hall field as the reconnection progresses which cause increase in parallel wavelengths, hence decrease in corresponding speeds. The waves have transverse propagation speeds greater than inflow as a result of which Hall field was observed to spread into the inflow. These waves are observed to carry enough energy which may be important for generation auroras as the precipitate in the ionosphere. Shay, M.A. \textit{et al.} PRL, 107(6), 065001 (2011). Sharma, P. \textit{et al.} JGR$:$ Space Physics ,123, 341–349 (2018). [Preview Abstract] 

NP10.00058: Electron Pressure Anisotropy Measurements on the Terrestrial Reconnection Experiment Rachel Myers, Jan Egedal, Joseph Olson, Samuel Greess, Alexander MilletAyala, Michael Clark, Douglass Endrizzi, John Wallace, Cary Forest The Terrestrial Reconnection Experiment (TREX) at the Wisconsin Plasma Physics Laboratory (WiPPL) studies collisionless magnetic reconnection with a guide field. In this regime, electron pressure anisotropy should develop, deviating from Hall reconnection dynamics and driving largescale current layer formation [1]. A multidirectional Langmuir probe measures this anisotropy. This probe contains three external tips and three shielded tips designed to rotate and detect directional electron flow from a full set of angles. Modifications to the IV characteristic depending on shielding and probe orientation relative to the magnetic field (measured by a 3D $\dot{B}$ pickup loop) display the extent of observed anisotropy in the collisionless reconnection region. Since the Langmuir tips are smaller than the Larmor radius, gyromagnetic effects can be ignored. Results and analysis from the probe are presented. [1] J. Egedal \emph{et al.}, Phys. Plasmas (2013). [Preview Abstract] 

NP10.00059: Order unity reconnection rate scaling during antiparallel magnetic reconnection on TREX Joseph Olson, Jan Egedal, Sam Greess, Alex MilletAyala, Rachel Myers, Cary Forest The Terrestrial Reconnection Experiment (TREX) is a device optimized to study the role of kinetic dynamics during collisionless magnetic reconnection\footnote{Olson, J., et al., Phys. Rev. Letters, \textbf{116}, 255001 (2016).}. In a recent experimental run consisting of $\sim900$ shots while varying certain experimental parameters we measured the reconnection rate using the CassakShay scaling for asymmetric antiparallel reconnection\footnote{Cassak, P.A., and Shay, M.A., Phys. of Plasmas, \textbf{14}, 102114 (2007).}. In this study, we observe that the absolute reconnection rate $E_{rec}$ is set by the applied drive voltage while being insensitive to the applied background field, ion species, or plasma density. However, for all epxerimental configurations the observed relative reconnection rate is $E_{rec}/(V_{A}B_{rec})\sim1$ instead of the expected rate of $E_{rec}/(V_{A}B_{rec})\sim0.1$. These experiments suggest that the reconnecting magnetic field selfregulates to match the externally applied drive in order to provide a selfconsistent reconnection rate. This has important implications for determining the parameters of any given reconnection experiment while also challenging the ubiquity of the 0.1 rate scaling for fast magnetic reconnection. [Preview Abstract] 

NP10.00060: Validation of Anisotropic Electron Fluid Closure Through In Situ Spacecraft Observations of Magnetic Reconnection Blake Wetherton, Jan Egedal, Ari Le, William Daughton A valid fluid model for electrons in collisionless space plasmas is desirable for understanding the structure and evolution of magnetic reconnection geometries. Additionally, such a fluid model would be useful for the simulation of systems too large to be tractable in a fully kinetic model. Using Magnetospheric Multiscale spacecraft observations, we provide direct confirmation of the Lê2009 equations of state for the electron pressure tensor during guide field reconnection and demonstrate how the closure can be applied in efficient numerical simulation, yielding new physical insight to the electron heating problem. Furthermore, we use the Lê2009 equations of state to predict a scaling of electron heating in the exhaust comparable to the available observational data. [Preview Abstract] 

NP10.00061: Time domain structures in magnetic flux rope experiments Shawn Wenjie Tang, Walter Gekelman, Patrick Pribyl, Stephen Vincena Time Domain Structures (TDS) are varieties of narrow, intense spikes that appear in the electric potential/field measurements of numerous space observations (e.g. in auroras, planetary magnetospheres) and in laboratory experiments. They appear to be produced by nonlinear processes related to plasma instabilities and are believed to be associated with the end state of turbulence. In an ongoing investigation at UCLA, TDS have been observed near the surface of two magnetized flux ropes produced within the LArge Plasma Device (LAPD). Two 11~m long kinkunstable flux ropes were created by a lanthanum hexaboride (LaB$_6$) source and are encapsulated within a 18~m long background plasma produced by a barium oxide (BaO) cathode. The TDS are observed only when the ropes are kink unstable. Preliminary analysis suggest that the TDS emanate from the reconnection region and migrate to the periphery of the moving ropes. In addition, these structures appear to have Lorentzian character (an indicator of chaotic behavior) and can couple to the kinking of the ropes when more power is delivered to the ropes. The structure of the TDS are currently under investigation through a crosscorrelation of the signal between two probes. [Preview Abstract] 

NP10.00062: Overview of the Keda Reconnection eXperiment (KRX) Weixing Ding, Jinlin Xie, Qiaofeng Zhang, Feibin Fan, Longlong Sang, Quanming Lu The Keda Reconnection eXperiment(KRX), a large linear magnetized plasma device with two parallel current plates has been designed and is being constructed at University of science and Technology of China for magnetic reconnections. The KRX is 10 meters long and 3 meters in diameter. Plasma with densities up to 10$^{\mathrm{13}}$cm$^{\mathrm{3}}$ is produced by discharge between a 2x2 m2 oxidecoated cathode and a grid anode. A pulsed axial magnetic field varying from 10 to 1000 Gauss is generated via 9 sets of magnetic coils to confine the plasma. The two parallel current plates supplied by an edge controllable current source are able to drive plasma reconnections. Furthermore the KRX not only develops multidimensional Langmuir probe and magnetic probe but also advanced optical diagnostic systems including Thomson scattering (TS), laser induced fluorescence (LIF) and THz polarimetryinterferometer system for reconnection study. The detail design and construction progress will be presented. The work is supported by Chinese Natural Science Foundation. [Preview Abstract] 
(Author Not Attending)

NP10.00063: Measurements of particle heating and acceleration during magnetic reconnection in EMHD regime Qiaofeng Zhang, Jinlin Xie, Feibin Fan, Longlong Sang, Quanming Lu, Ge Zhuang, Weixing Ding Magnetic reconnection provides a physical mechanism for fast conversion from magnetic energy to plasma kinetic energy. Particle heating and acceleration measurements are important to understand this process. The magnetic reconnection is investigated on linear magnetic plasma device, where timevarying currents through two parallel aluminum rods produce a magnetic reconnection configuration. Electron energy distribution function (EEDF) is measured by energy grid analyzer, and ion velocity distribution function (IVDF) is measured by laser induced fluorescence (LIF) in argon plasmas. The evolutions of EEDF and IVDF during the reconnection process will be presented. Also the relevance to the different background plasma parameters and inflow drives will be given. [Preview Abstract] 

NP10.00064: Reconnection experiments in EMHD regime with controllable driving Feibin Fan, Longlong Sang, Qiaofeng Zhang, Quanming Lu, Weixing Ding, Jinlin Xie In this work, we conduct an electron magnetohydrodynamics (MHD) magnetic reconnection experiment with guidefield in the Keda linear magnetized plasma (KLMP) device. Two parallel aluminum sticks in axial direction with a separation distance 10 cm are installed in the vacuum chamber. The reconnection field is produced via two identical pulsed currents in same direction applied on the sticks. The ramp up rate of the pulse current is controllable in order to provide inflow drives with different speed. The resistivity is found anomalous which is much larger than the transverse spitzer resistivity. It is also found that the lager drive result in enhanced anomalous resistivity. The generalized Ohm law is studied near the Xpoint. It is found that the collisional resistive term and electron inertial term are not enough to balance the measured reconnection electric field, which means the electron pressure term is dominant near the Xpoint. [Preview Abstract] 

NP10.00065: A Semianalytical Framework for 1D Shock Hydrodynamics with Application to HED Systems Michael Wadas, Eric Johnsen Interfaces separating media of different densities undergoing strong accelerations play important roles in high energy density (HED) systems, including dynamic compression and hydrodynamic instability studies. Our objective is to develop a framework for semianalytically solving the onedimensional Euler equations in planar geometries in the context of designing and analyzing HED experiments. By combining the method of characteristics with boundary conditions prescribed by the exact solution to the Riemann problem, it is found that semianalytical solutions can be obtained for onedimensional planar flows involving any combination of interactions of shock and rarefaction waves with fluid interfaces. The solutions obtained using this method are computationally less expensive and more physically insightful than their numerical counterparts, evidenced by their comparison to solutions obtained using an inhouse, highorder accurate discontinuous Galerkin code. [Preview Abstract] 

NP10.00066: Kinetic Modeling of Collisional Shocks Using OSIRIS Josh May, Rui Hua, Mathieu BaillyGrandvaux, Farhat Beg, Warren B Mori Using the particleincell code OSIRIS along with a binary Coulomb collision scheme, we study shock experiments which were performed on OMEGAEP. In the experiments, shocks are formed by an ablatordriven Si0$_2$ piston entering mixtures of noble gasses at standard temperature and pressure. The shocks can be observed after $3 ns$ traveling at velocities of roughly $0.002 c$. OSIRIS results indicate, first, that these shocks are collision mediated, as ionelectron temperature equalization (also collision driven) happens too rapidly for an ionacoustic shock to be sustained. Second, they indicate that the plasma remains kinetic throughout the shockformation process, and in particular that a fluid shock front cannot form in this rapidly with a uniform piston velocity; however using an accelerating piston or plasma can give consistent results. [Preview Abstract] 

NP10.00067: Characterization of jetdriven shocks in multiionspecies plasmas Maximilian Schneider, Ameer Mohammed, Matthew Carrier, Andrew Watson, Colin Adams Collisions are induced in high velocity $(\sim15~\mathrm{km/s})$, low density $(\sim10^{16}~\mathrm{cm^{3}})$ plasma jets accelerated by a small linear plasmaarmature railgun. The railgun is gasfed with pure argon which mixes with both low and highZ impurities ablated from the gun’s plasmafacing components to produce a multipleion species plasma jet. Characteristics of freeexpanding jets inferred from a full suite of diagnostics including a twochord MachZehnder heterodyne interferometer, $750~\mathrm{mm}$ highresolution imaging spectrograph, and intensified CCD camera suggest that jets are low temperature $(\sim2~\mathrm{eV})$ and initially exist in a collisional regime, resulting in a centimeterscale shock structure when jets collide with stagnant plasma. Preliminary results provide insight regarding the spatial distribution of ion species before and after the collision. Repeatability of structures observed during collisions and prospects for control of jet composition will also be addressed. [Preview Abstract] 

NP10.00068: Bremsstrahlung in marginally collisional plasma flows T.E. Weber, I.A. Bean, C.S. Adams, D.R. Welch Radiative processes in marginally collisional plasmas are complex and are not amenable to many simplifying assumptions commonly made in plasma physics, especially in highly dynamic systems such as shocks. The details of the energy partition between thermal or nonthermal populations, highenergy particles, enhanced magnetic fields, and/or radiation can vary greatly depending on the Magnetosonic Mach number, Knudsen number, Hall parameter, and plasma beta. Kinetic simulations, experiments, analytical scaling, and limiting approximations are used to gain an understanding of radiation emission in this challenging regime. One area of interest is ``hard'' xray emission from 10  100 keV; a range that may prove promising for diagnosing the kinetics of highenergy populations and one that is important for the development of laboratory sources such as those fielded on NIF and Z. [Preview Abstract] 

NP10.00069: Acceleration of electrons and maser radiation from collisionless shocks R. Bingham, R. Bamford, R. Trines, B. Kellett, R.A. Cairns, D. Speirs, K. Ronald, A. Phelps, M. Koepke, F. Cruz, R. Fonseca, L. Silva, A. Rigby, G. Gregori Collisionless shock waves arise in many areas of laboratory and space plasmas, such as the Zpinch and theta pinch, plasma accelerators, laser fusion, planetary bow shocks, artificial releases, solar flares and CMEs, pulsars, jets, accretion discs, and galaxy clusters. Collisionless shocks are responsible for energizing particles and nonthermal electromagnetic emission from the accelerated electrons. One of the mechanisms in producing energetic electrons at low Mach number magnetized collisionless shock waves is through the generation of lowerhybrid turbulence via shockreflected ions and acceleration of electrons by the lowerhybrid waves. These accelerated electrons can either radiate cyclotron maser radiation if magnetically compressed by moving into stronger field regions or generate EM waves via the creation of Langmuir waves which subsequently undergo inverse twoplasmon decay. [Preview Abstract] 

NP10.00070: OutofPlane Motion in a Shocked 2D Dusty Plasma Anton Kananovich, John Goree A 2D dusty plasma is prepared, in an experiment, as a layer of micrometersize monodisperse particles, levitated in the sheath above the lower electrode in a lowtemperature plasma. The microparticles acquire large electrical charges and become stronglycoupled. Particles are confined vertically by a deep potential well, due to the combination of an upward electric force from the sheath, and the downward force of gravity. In the horizontal direction, they are confined by a much more gentle potential well, due to the sheath’s curvature. Normally the microparticles remain always in a single layer, but in this experiment, extreme compression is applied by the propagation of a shock. We find that this extreme compression causes some microparticles to be pushed briefly out of the layer. This splitting or ``buckling'' of the layer was studied in experiment. A simple analytical model was developed to explain the buckling. [Preview Abstract] 

NP10.00071: Microscopic Characterization of Shocks in 2D Dusty Plasma Anton Kananovich, John Goree A dusty plasma is formed by immersing polymer microspheres in a glowdischarge plasma. Due to their size, the microspheres gain a large electric charge, so that they are strongly coupled. We report studies of shocks in a dusty plasma, under these strongcoupling conditions. We form a single 2D layer, which we observe using videomicroscopy with particle tracking analysis, yielding the positions and velocities of individual particles. We exploit this diagnostic to study the microscopic arrangement of the microspheres, as a shock passes through them. Starting with a crystalline microstructure, we excite a shock with a moving wire, and the shock melts the crystal. We investigated the spatiotemporal character of this melting using the particlelevel data, by identifying defects using Voronoi and polygon analysis. Using the trajectories of individual particles in the vicinity of the shock, we plan to characterize the shock thickness and shock speed. [Preview Abstract] 

NP10.00072: Dust levitation in a modulated afterglow plasma Neeraj Chaubey, John Goree, Anton Kananovich The radiofrequency power for a glowdischarge plasma is switched on and off, repeatedly, so that the source of ionization is present only a fraction of the time. In this plasma, we introduce 8.7 micron diameter polymer spheres, to make a single layer dusty plasma. The RF power is modulated on and off at 1 kHz, with a duty cycle $ \ll 50 \%$. The majority of the time, when the RF power is off, the plasma has an afterglow condition. The dust particles are levitated by the timeaverage upward electric force, balanced by the downward force of gravity. In our experiment, the upward electric force is provided by the negative sheath, just above the powered electrode. It is found that the single dust layer can be lowered, near the electrode, with this modulation scheme. When the dust layer has a crystalline microstructure, the crystal is preserved but expanded laterally, when we modulate the RF power. [Preview Abstract] 

NP10.00073: Dusty Plasma Experiment for Measuring the Dynamic Structure Factor Vitaliy Zhuravlyov, John Goree, ChunShang Wong, Jorge Berumen The physics of strongly coupled plasmas can be studied experimentally using a dusty plasma. An advantage of dusty plasmas is that the particles can be tracked using video microscopy. An experiment is planned, with a 2D monolayer of polymer microspheres levitated in an RF plasma, to measure the dynamic structure factor, $S(k, \omega)$, which is a measure of the viscoelasticity of a strongly coupled plasma. The dynamic structure factor reveals the time scales and length scales for (elastic) energy storage as compared to (viscous) energy dissipation, for the collective motion of the microspheres. We use laser heating to maintain the monolayer at a constant temperature, under liquidlike conditions without shear flow. The motion of microspheres is recorded by a highspeed video camera. Image analysis yields particle positions in each video frame, which are used as inputs for calculating $S(k, \omega)$. We plan to compare our experimentally measured $S(k, \omega)$ with theoretical models including those of Mithen \textit{et al.} \footnote{J. P. Mithen, J. Daligault, B. J. B. Crowley, and G. Gregori, Phys. Rev. E, 84, 046401 (2011).} [Preview Abstract] 

NP10.00074: Experiment for Characterizing Viscoelasticity in a 2D Dusty Plasma with Shear Flows Jorge Berumen Cantu, John Goree, Vitaliy Zhuravlyov Viscoelasticity is a property of strongly coupled plasmas characterizing their combination of dissipative (viscous) and energy storing (elastic) properties. Dusty plasmas are well suited for experimental studies of this effect. With their large size, the particles have a large charge and therefore leads to strong coupling. Their size also allows for individual tracking of the particles. We describe an experiment that is underway in a modified Gaseous Electronics Conference (GEC) chamber with a capacitively coupled RF power to sustain the plasma. Polymer microspheres are suspended by the timeaverage electric field in the sheath above the lower electrode. Laser heating is used to maintain a steady temperature in the dust cloud. A lasergenerated shear flow in the particle layer is modulated at a frequency $\omega$. We characterize viscoelasticity as a frequencydependent viscosity $\eta (\omega)$, where $\eta (\omega)$ is defined as the ratio of shear stress $P_{xy}(\omega)$ over the shear rate $\gamma(\omega)$. A highspeed, highresolution camera is used to record a video of the particles, and image analysis yields their individual positions and velocities which are the required inputs for calculating $P_{xy}(\omega)$ and $\gamma(\omega)$. [Preview Abstract] 

NP10.00075: Nonlinear dust acoustic waves in a plasma under microgravity conditions. Bin Liu, John Goree, Mikhail Pustylnik, Hubertus Thomas, Vladimir Fortov, Andrey Lipaev, Alexander Usachev, Vladimir Molotkov, Oleg Petrov, Markus Thoma Nonlinear dust acoustic waves were investigated in a plasma under microgravity conditions, using the European Space Agency facility PK4 on the International Space Station (ISS). A large threedimensional cloud of dust particles was confined near a radiofrequency coil that powered a glow discharge in lowpressure neon gas. Lowfrequency dust acoustic waves were spontaneously excited, due to the flowing ions in the plasma. The waves were nonlinear, with a large amplitude. Experimental spectra for dust particle motion were obtained, using the particle position data from an analysis of the images of the particle motion. Nonlinear phenomena are discussed, including nonsinusoidal waveform shape and indicator of wave synchronization. All authors acknowledge the joint ESA/Roscosmos ``Experiment Plasmakristall4'' onboard the International Space Station. Work was partially supported by DLR Grant Nos. 50WM1441 and 50WM1742. Work at Iowa was supported by NASAJPL subcontracts 1573629 and 1579454, and the NSF Award No. 1740379. [Preview Abstract] 

NP10.00076: Propagation characteristics of nonlinear dust acoustic waves in inhomogeneous complex plasmas Garima Arora, Pintu Bandyopadhyay, M.G Hariprasad, Abhijit Sen An experimental investigation of the propagation characteristics of nonlinear Dust Acoustic Waves (DAWs) in inhomogeneouscomplex plasmasis presented. The experiments have been carried out in a $\Pi $shaped dusty plasma experimental (DPEx) device with micron sized Kaolin particles embedded in a DC glow dischargeArgon plasma. The dust density inhomogeneity along the axial direction of the device is created by a slight imbalance of the pumping rate and the gas flow rate. NonlinearDAWsare excited by compressing the dust fluid during the generation of dust flow and are observed to propagate away from the anode. The effect of the dust density inhomogeneity is investigated on the propagation characteristics of nonlinear Dust Acoustic Waves by analyzing the successiveimages, which are recorded using a high speed camera.It is found that the wave amplitudes and phase velocities increases with the decreaseof dust density along the length of the dust cloud. Our experimental observations for these high amplitude DAWs are found to be consistent with existing fluid theories for the propagation of nonlinear DAWs in inhomogeneous complex plasmas . The details of the experimental procedure and the results will be presented at the conference. [Preview Abstract] 

NP10.00077: How the Dust Acoustic Wave Initiates the Taylor Instability in the Vertical Plane Katherine Pacha How the dust acoustic wave creates the Taylor instability in a laboratory dusty plasma are presented. The Taylor Instability was triggered by the dust acoustic wave creating an instability along the vertical interface of the cloud which allowed the lowdensity dust fluid into the highdensity dust fluid. Reflection of the dust acoustic wave aides in its strength. [Preview Abstract] 

NP10.00078: Kinetics effects in a plasma crystal induced by an electron beam Jeremiah Williams, Catalin Ticos, Dorina Ticos, Adrian Scurtu, Lori Scott, Edward Thomas The kinetic effects on the dust particles in a plasma crystal locally irradiated by a narrow, pulsed electron beam (EB) with energies from 10 – 15 keV are presented. In the irradiation zone, the EB pushes the dust particles, leading to both laminar and turbulent flow. Particle image velocimetry is applied to measure the flow characteristics of the dust and strong transversal heating of the dust particles is observed where the EB impacts the plasma crystal. This poster presents experimental measurements and molecular dynamic simulations of the interaction of an EB with a plasma crystal. [Preview Abstract] 

NP10.00079: Impedance Probe Measurements in Dusty Plasma Brandon Doyle, Uwe Konopka, Taylor Hall, Edward Thomas, Jr. Impedance probe measurements are a type of active plasma resonance spectroscopy which utilize plasma resonances at or near the electron plasma frequency, $\omega_{\mathrm{pe}}$. In this work, we use a twopronged impedance probe to measure the frequencydependent transmission of RF signals through plasma. We analyze shifts in these transmission spectra while changing a) the quantity of dust in the plasma, or b) the orientation of the probe with respect to an external magnetic field. Adding dust to a plasma affects $\omega_{\mathrm{pe}}$ as dust becomes charged. The dust charge is typically highly negative because of the higher mobility of electrons compared to ions. The negative dust charging leads to a reduction in the electron density in the surrounding plasma and a reduction in $\omega_{\mathrm{pe}}$ related to this electron density depletion. The results from the first experiment presented here reflect this electron density depletion. In the case of magnetized electrons, the electron mobility is greatly reduced in directions perpendicular to the magnetic field, which affects impedance probe transmission. The second experiment presented explores this anisotropy. [Preview Abstract] 

NP10.00080: Ion Flows and Ion Temperature in Magnetized Dusty Plasmas Evan Aguirre, Edward Thomas We report measurements of the ion velocity distribution function (IVDF) in magnetized and unmagnetized dusty plasmas. Measurements were obtained using laser induced fluorescence (LIF) by injecting the laser perpendicular and parallel to the background magnetic field for a variety of plasma conditions. We present measurements of the ion flow in three locations of interest: the bulk plasma, the dust cloud, and the plasma sheath just above the electrode. The spatial region surrounding the dust cloud is studied in detail with resolution of 3 mm. Current theories of the equilibrium flow have not been firmly established by experimental results, which are currently lacking. We also discuss implementation of LIF to the Magnetized Dusty Plasma Experiment (MDPX) and other dusty plasmas with high magnetic fields (B \textgreater 1 T) and pressure (P \textgreater 20 mTorr) where LIF generally ceases to function. [Preview Abstract] 

NP10.00081: Current research on the Magnetized Dusty Plasma Experiment (MDPX) device Edward Thomas, Uwe Konopka, Robert Merlino, Marlene Rosenberg The Magnetized Dusty Plasma Experiment (MDPX) device at Auburn University is a highly flexible, high magnetic field (B \textgreater 3 T) research instrument with a mission to serve as an open access, multiuser facility for the dusty plasma, basic plasma, and fusion plasma research communities. In the last year, the MDPX device has extended its operational capabilities by incorporating different experimental chambers, performing new studies of particle growth at high magnetic field, and performing new experiments and modeling to gain insights into pattern formation in both the background plasma and the dusty plasma due to the high magnetic field. This presentation will summarize results from these studies and will present initial design concepts for the next generation of plasma and dusty plasma diagnostics and experimental capabilities for the MDPX device. [Preview Abstract] 

NP10.00082: Dust void formation within magnetized dusty plasmas Spencer LeBlanc, Edward Thomas Dustfree regions (dust voids) within complex plasmas have been observed and studied in a wide variety of complex plasma environments and parameter regimes, including dust monolayers, microgravity systems, and threedimensional earthbased dust clouds. Often formed by a local concentration and transport of charge within the plasma bulk, the charged dust particles can be used as a diagnostic tool to visualize the void region in the plasma. Consequently, measurements and analysis of the dust particle confinement in the region of the void can reveal detailed information about the background plasma system. At Auburn University's Magnetized Plasma Research Laboratory (MPRL), dust voids have been investigated in plasmas under varying degrees of ion magnetization, yielding new insight into the dustcharging processes, and the ion drag (or ion wind) force on dust grains, as well as the influence of external magnetic fields applied to these phenomena. Experimental measurements of the voids under a variety of magnetic field configurations and their connection to underlying ion dynamics are presented. [Preview Abstract] 

NP10.00083: Finite dust clusters under strong magnetic fields Andre Melzer, Harald Krueger, Stefan Schuett, Matthias Mulsow Dusty plasmas consist of (micronsized) dust particles trapped in a gaseous discharge plasma. The effects of magnetic fields on such dusty plasmas have attracted high interest, recently, due to the availability of superconductive magnets. Here, experiments on dust clusters of micronsized particles have been performed. The clusters are trapped in the sheath of an rf discharge and their dynamics is measured for different magnetic field strengths ranging from a few milliteslas to 5.8 T. From the normal modes of the clusters various dust properties such as the kinetic temperature, the dust charge and the screening length are derived. [Preview Abstract] 

NP10.00084: Investigations into the control of dust charge in complex plasmas Michael McKinlay, Edward Thomas, Jr. Because the properties of complex (dusty) plasmas are directly coupled to the properties of the background plasma that the particles are suspended in, they have great potential as highly localized plasma diagnostic tools. However, this potential can be limited by the lack of direct control over the most fundamental of dust properties  the particle charge. Recent experiments at the Auburn University Magnetized Plasma Research Laboratory (MPRL) have found evidence that low power (a few mW) electric fields oscillating at frequencies above the dustplasma frequency, but below the ionneutral collision and ionplasma frequencies, may provide a method of controlling the dust charge without radically altering the properties of the background plasma. Probe measurements and data from video analysis are presented alongside estimates of the change and a theory of the effect of the signals on the charging currents. A second experiment that investigates the possibility of using a controlled application of UV light to modify the dust particle charge in the plasma is also presented. [Preview Abstract] 

NP10.00085: Status of Development of Laser Induced Fluorescence Diagnostic for a Dusty Plasma Ryan S Marshall, Armin Ewert, Paul M Bellan Laser Induced Fluorescence (LIF) provides the temperature and flow velocity of plasma neutrals or ions by measuring their velocity distribution directly via Doppler Shift. An ultranarrow, tunable diode laser is used to pump the 696 nm neutral Argon line in the Caltech WaterIce Dusty Plasma Experiment with LIF emission detected at 772 nm. The LIF diagnostic gives reasonable, reproducible measurements of the neutral atom temperature both with and without ice grains. The laser frequency is controlled with $\sim1.5$ MHz resolution (i.e., 1 part in $10^8$) corresponding to a $\sim1$ meter per second smallest detectable flow velocity. Despite this precision, no flow has been detected so far. A major difficulty is that the laser wavelength drifts over time. To combat this, PID stabilization is being applied to further improve the velocity resolution. Also, vacuum pump vibrations that slightly modulate the transmission of the vacuum window have been attenuated. Concurrently, a wall of magnets has been used to improve confinement and allow lower pressure operation in an unsuccessful attempt to obtain ion LIF (different wavelengths used) measurements. [Preview Abstract] 

NP10.00086: Laser Induced Fluorescence to measure flow velocity of Argon neutrals in a plasma environment Armin Ewert, Ryan Marshall, Paul Bellan Laser Induced Fluorescence (LIF) is being implemented on the Caltech WaterIce Dusty Plasma Experiment to measure the neutral particle velocity. Argon neutrals are excited by a chopped 696 nm tunable diode laser having \textless 1 MHz line width. An unchopped sample of the laser beam passes through the plasma to a photodiode to provide a signal for a PID controller that stabilizes the laser frequency.~The 772 nm fluorescence emitted by the excited argon neutrals is detected by a photomultiplier connected to a lockin amplifier synchronized to the chopper. The system now resolves~1 m/s but the flow velocity appears to be much slower as the measurements are irreproducible other than showing that the velocity is less than 1 m/s. This irreproducibility (large error bar)~results from a small drift of the lockin signal. A search for the cause of this drift is underway by looking for correlations of drifts of various parameters with the lockin drift. At the time of writing a prime suspect is the slightly changing laser wavelength that might be caused by plasma variations as it is used to lock the wavelength to a defined absorption level. Finding the cause of the lockin drift and then eliminating it should enable resolving much slower velocities. [Preview Abstract] 

NP10.00087: DustTracking Analytical Tools for Low Speed Camera Recording in Plasma Discharges Jorge Carmona Reyes, Ke Qiao, Michael Cook, Kenneth Ulibarri, Jei Kong, Lorin Matthews, Truell Hyde Video data gathered from the PlasmaKristal4 (PK4) laboratory on the International Space Station (ISS) is usually recorded at 35 to 70 frames per second. This poses a challenge for tracking individual particle positions, velocities and/or accelerations when the particle motion is such that they cannot be individually resolved at such slow frame rates. However, analysis of this video data is still possible using tools which allow measurement of group phase velocities, particle motion frequencies, particle accelerations, linear and angular direction and overall behavior of the particles. Using CASPER's BUPK4 ground analog, a map between particle streaking and particle tracking has been assembled which allows correlations between particle streaks and individual particle positions to be determined. Additional analytical tools, useful for development of spacetime charts, anisotropic scaling indices and the collection of highspeed data (\textgreater 50,000 FPS) to determine the presence of ionization waves will also be reviewed. The manner in which these techniques can be used for analysis of PK4 (ISS) data will also be discussed. [Preview Abstract] 

NP10.00088: Charge Analysis techniques for Magnetized Dusty Plasma Flows Dylan Funk, Uwe Konopka, Edward Thomas Dusty plasmas consist of the standard plasma components (electrons, ions and neutrals) as well as micrometer sized particles. The dust particles are in general highly charged as a result of their interaction with the other plasma components. The charge of these dust particles is, in general, a difficult quantity to estimate precisely, especially when under the influence of a magnetic field. Because of this difficulty, a method for the experimental determination of the dust particle charge under the influence of a magnetic field is required. We will demonstrate the experimental setup we developed for investigation of this dust charge. Our method utilizes the Lorentz force acting on the moving particles due to the static magnetic field. A dust particle density gradient will build up due to the Lorentz force. We plan to use these methods on the Magnetized Dusty Plasma Experiment (MDPX) at Auburn University. We plan to compare this experimental data to the results from our molecular dynamic simulation (MD). [Preview Abstract] 

NP10.00089: First order Phase Transition in DC discharge Complex Plasmas Hariprasad MG., Saravanan A., Garima Arora, Pintu Bandyopadhyay, Abhijit Sen We report the first order phase transition in a strongly coupled twodimensional DC discharge complex (dusty) plasma. Experiments are carried out in Dusty Plasma Experimental (DPEx) Device in which complex plasma is produced by using monodispersive MF particles in the background of a DC glow discharge Argon plasma . An explosive full melting of the dusty plasma crystal is observed with a negligible decrease in neutral gas pressure (0.1 Pa). The dust temperature dramatically increased to approximately 50 eV from 2 eV and the Coulomb coupling parameter changed to approximately 7 from 220. Structural analysis of twodimensional crystal and liquid is carried out through a number of analysis like pair correlation function, Voronoi diagram and Delaunay triangulation. The balancing of dust neutral collision and the vertical oscillation of the dust crystal is understood as the mechanism, which drives the phase transition. [Preview Abstract] 

NP10.00090: Ice Dusty Plasma Experiment Upgrade to use Cryocoolers Paul Bellan Tiny ice grains immersed in plasma occur in noctilucent clouds, Saturn's rings, comet tails, and accretion disks. Experiments at the Max Planck Institut [1] and at Caltech [2,3] showed that ice grains spontaneously form from water vapor in a weakly ionized plasma if the background gas is made extremely cold via contact with refrigerated electrodes. Photos show [2,3] that the ice grains are long and spindly in contrast to the spherical shape commonly assumed in theoretical models; the grain length can exceed half a millimeter and the intergrain spacing is a fraction of millimeter. The Caltech experiment is being upgraded to have the electrode cooling provided by liquid helium refrigerated cryocoolers; these will replace the liquid nitrogen Dewars now in use. The cryocoolers will provide both a temperature scanning capability and a much lower attainable temperature. These new features open up a new operational dimension and will allow determining the temperature dependence of plasmainstigated ice dust formation, growth, and composition. The design and construction status will be presented. [1] S. Shimizu et al. (2010), JGR 115, D18205. [2] K. B. Chai and~P. M. Bellan~(2015)~ApJ 802, 112. [3] R. S. Marshall, K. B. Chai, and~P. M. Bellan~(2017)~ApJ 837, 56. [Preview Abstract] 

NP10.00091: Investigating the Thermal Properties of a Complex Plasma Lori Scott, Edward E Thomas Jr., Uwe Konopka, Jeremiah Williams, Mikhail Pustylnik, Hubertus Thomas Complex plasmas are a fourcomponent plasma system composed of electrons, ions, neutrals, and micronsized, charged particles (dust). The large mass of the dust particles leads to their compression to thin layers when influenced by gravity, but under microgravity conditions, the particles can fill the entire plasma volume which allows the study of smaller interparticle forces that are masked by gravity. To overcome the gravitational influence, we use the dc glow discharge Plasma Kristall4 (PK4) microgravity laboratory on the International Space Station (ISS). When dust particles are injected into PK4, they flow along an axial electric field until stopped by the application of a periodic oscillation of the electric field. This oscillation creates a change in the spatial ordering and thermal state of the dust system. We seek to understand the redistribution of kinetic energy of the dust particles at the onset of this periodic oscillation. This presentation will focus on data obtained using the ground science reference module, initial results from an ISS experiment, and supporting molecular dynamics simulations. [Preview Abstract] 

NP10.00092: Testing Thermal Conductivity Models with Equilibrium Molecular Dynamics Simulations of the One Component Plasma Brett Scheiner, Scott Baalrud Equilibrium molecular dynamics (EMD) simulations are used to calculate the thermal conductivity of the one component plasma (OCP) via the GreenKubo formalism. These simulations address previous discrepancies between the OCP thermal conductivity calculated from EMD and nonequilibrium MD. Analysis of heat flux autocorrelation functions show that very long (6 x 10$^{\mathrm{5}} \quad \omega_{\mathrm{p}}^{\mathrm{1}})$ time series are needed to reduce the noise level to allow accurate time integration. The new simulations provide the first accurate data in the range 0.1 \textless $\Gamma $ \textless 2, allowing the evaluation of thermal conductivity models in a regime where they are predictive. We test calculations of thermal conductivity using generalized Coulomb logarithms from the theories of LeeMore, LandauSpitzer, TanakaIchimaru, and BaalrudDaligualt and find that only the latter two can reproduce the trend of the MD data for 0.1 \textless $\Gamma $ \textless 10. The results provide the first test of the LandauSpitzer thermal conductivity using MD and indicate that transport theories must include the effect of particle correlations to properly model $\Gamma $ \textgreater 0.3. None of the evaluated theories are found to accurately model the OCP for $\Gamma $ \textgreater 10. [Preview Abstract] 

NP10.00093: A dualspecies MOTion trap Robert Sprenkle, Scott Bergeson We report on progress to create a hybrid dualspecies calcium and ytterbium magnetooptical trap (MOT) superimposed onto a linear quadrupole trap. This “MOTion” trap will allow us to trap neutral atoms in the MOT, ionize them using nsduration pulsed lasers, and trap the resulting plasma in the quadrupole trap. Driving the trap at two frequencies we will eliminate centrifugal separation inherent in simultaneous trapping of diﬀerent mass ions. The primary goal of this experiment is to measure collisional momentum transfer between the Yb$^+$ and Ca$^+$ ions as a means of determining plasma transport properties in a strongly coupled plasma environment. Using carefully aligned probe laser beams and spatial imaging of the ion ﬂuorescence, we anticipate being able to distinguish between the coherent ion micromotion and the thermal ion motion in the plasma. [Preview Abstract] 

NP10.00094: Computational Modeling of Offresonant RF Heating of Ultracold Plasmas to Obtain Electronion Collision Rates Puchang Jiang, John Guthrie, Jacob Roberts Offresonant RF excitation of electron oscillations can be used in ultracold plasmas to measure electronion collision rates. This measurement is accomplished by determining the amount of heating imparted by such RF excitations. In this poster, we present computational modeling of the electronion collision rate and the associated RF heating as a function of parameters such as electron temperature/strong coupling, electron magnetization, and RF field parameters. [Preview Abstract] 

NP10.00095: Plasma chemistry modeling of an argon fluoride laser Tzvetelina Petrova, Matthew Wolford, George Petrov, Matthew Myers, John Giuliani, Malcolm McGeoch, Andrew Schmitt, Steve Obenschain An argon fluoride, 193 nm laser utilizing the Electra electron beam facility is under development at the U.S. Naval Research Laboratory (NRL). We are using both numerical modeling and experiments to study and predict the laser characteristics as well as understand the nonequilibrium plasma media. The model includes coupled nonequilibrium electron kinetics based on numerical solution of the electron energy Boltzmann equation [1], a timedependent 1D hydro model for the species transport and 3D model for the emitted and amplified radiation in argonfluoride ebeam generated plasma (ArF Orestes model). The plasma chemistry module includes reactions with thermal and beam electrons, neutral two and threebody reactions, ionion, and ionneutral reactions. In this work we study a double pass amplifier and oscillator configurations. Small signal gain, nonsaturable absorption, saturation intensity, laser yield and efficiency of ArF* were measured for code validation and building predictive capabilities for advancing design of largescale ArF lasers with short wavelength, broad bandwidth, and high efficiency, optimized for inertial confinement fusion applications [2]. [1] G. M. Petrov, \textit{et. al.,} JAP 122 (2017) 133301. [2] M. Wolford, \textit{et. al.,} IFSA2019. * Work supported by the NRL Base Program. [Preview Abstract] 

NP10.00096: Datadriven predictive science for lowtemperature plasmas Zhehui Wang, Walter Gekelman, Ayan Biswas, Christopher Biwer, Weng W. Chow, James Colgan, Gian Luca Delzanno, John Foster, Yogesh Gianchandani, Han Htoon, Earl Lawrence, Alex Peterson, Ghanshyam Pilania, Patrick Pribyl, Earl Scime, Stephen Vincena LANL, Sandia, UCLA, University of Michigan, West Virginia University, Lam Research Corporation, and collaborators propose to form a new center for predictive science of lowtemperature plasmas. The center’s mission is to demonstrate capabilities to predict and control plasma kinetics in eV lowtemperature regime such as in semiconducting processing plasmas. The center is founded on the emerging ‘fourth paradigm’ for scientific discovery and technology development, which uses rapidly advancing big data technologies and methods. The generation, processing, and applications of large experimental and simulation data sets coherently link interdisciplinary center expertise in experiments, plasma theory \& simulations, and statistical methods \& machine learning, culminating in predictions and controls. The new and potentially revolutionary diagnostics and sensors include Micro Electro and Mechanical Sensor probes, microparticle cloud imaging, nanoprobes enabled by nanocrystal and quantum dots. Existing experiments will be leveraged. [Preview Abstract] 

NP10.00097: Scaling of power consumption in onehole surface dielectric barrier discharge (DBD) Theophile Bonnet, Daoman Han, Yevgeny Raitses, Shurik Yatom Larger area surface DBDs with multiple holes have been extensively studied in the past \footnote{Jochen Kriegseis, Benjamin Möller, Sven Grundmann, Cameron Tropea, \textbf{"Capacitance and power consumption quantification of dielectric barrier discharge (DBD) plasma actuators"}, \textit{Journal of Electrostatics} \textbf{69} (2011) 302312.}. In this work, we study onehole surface DBDs with the aim to understand the power scaling with the hole diameter. The DBD device is made of two machined copper electrodes separated with a dielectric film made from a polyamide material. One of the electrodes has a hole. In the described experiments, electrical characterization with Lissajous figures correlated with imaging have been made with respect to the hole size. That allows to determine the power consumption, mode of the DBD operation including, diffusive or filamented, and the transition between these two modes as the function of the power for different hole sizes. [Preview Abstract] 

NP10.00098: Modification of particle growth in a highly magnetized argonacetylene plasma. Surabhi Jaiswal, Vincent Holloman, Lenaic Couëdel, Edward Thomas Nanoparticle growth in plasmas is of strong research interest due to its implications in astrophysical, industrial, and fusion plasma applications. In the presence of a high magnetic field, nanoparticle growth can be even more complicated where these particles generated due to plasma surface interaction and their presence can significantly affect the electrical properties of the plasma. In this presentation, an experiment on nanoparticle growth in highly magnetized argonacetylene plasma is presented. In these studies, the magnetic field alters the plasma dynamics and at very high magnetic field (B $\ge $ 1 T) a `filamentary structure' (which is a distinct, localized regions within a plasma that appears brighter than the surrounding plasma and that extends parallel to the magnetic field lines) forms in between the electrode. It is found that the nanoparticles grown in the plasma can act as a ``sink'' for the filamentary structure leading to them being suppressed. Simultaneously, particles grown in these filamentary structures significantly affect the particles morphology. This presentation reports on the effect of magnetic field on particle growth and discusses the exsitu analysis of the properties of grown nanoparticles. This work is supported with funding from the NSF EPSCoR program (OIA1655280) and the NSF/DOE Partnership in Basic Plasma Science and Engineering programs. [Preview Abstract] 

NP10.00099: Synthesis of highly crystalline boron nitride nanotubes using plasma jet Minseok Kim, JeongHwan Oh, SeungHyun Hong, Yong Hee Lee, TaeHee Kim, Sooseok Choi Boron Nitride Nanotubes (BNNT) have triggered considerable attention from industrial fields due to their tantalizing characteristics such as mechanical, electron field emission, piezoelectric, thermal, optical, and biocompatible properties since it synthesized in 1995. In spite of this considerable attention, the low production rate is a conclusive obstacle to apply them in the various industrial fields. Therefore, it requires to improve the BNNT synthesis system to a broad possibility of them into industrial applications such as optoelectronic device and reinforcements for structural composites. In this work, we suggest that it is suitable to introduce triple direct current (DC) thermal plasma jet system with hydrogen injection for a scalable synthesis of BNNT since it has more advantages to produce smalldiameter BNNT due to higher quenching rate of DC thermal plasma jet than induction thermal plasma jet in general. Additionally, the effect of hydrogen in the BNNT synthesis system is chemically discussed with Gibbs free energy for chemical reactions using HSC Chemistry. [Preview Abstract] 

NP10.00100: Heat and particle fluxes of KAERI divertor plasma simulator based on high power AFMPD thruster KilByoung Chai, DuckHee Kwon A divertor plasma simulator which can provide high heat and particle fluxes to a target has been constructed at Korea Atomic Energy Research Institute (KAERI) using AppliedField MagnetoPlasmaDynamic (AFMPD) thruster concept. An AFMPD thruster, a kind of electric propulsion, is typically powered by several hundred of kilowatts DC power supply and can generate very high density plasmas at the low pressure similar to fusion divertor region. Our facility will be used to study and develop divertor materials and heat sink designs that can handle heat flux of 10 MW/m$^{\mathrm{2}}$ and particle flux of 10$^{\mathrm{24}}$ /m$^{\mathrm{2}}$/s. At present, we have successfully developed our plasma source and the heat flux provided by our divertor simulator is measured to be 2.5 MW/m$^{\mathrm{2}}$ by a single channel calorimeter consisting of copper block and several thermocouples. The measured particle flux is in the order of 10$^{\mathrm{23}}$ /m$^{\mathrm{2}}$/s by optical emission spectroscopy with collisionalradiative model and a Langmuir probe. [Preview Abstract] 

NP10.00101: Helicon Plasma Thruster Employing Rotating Magnetic Field Plasma Acceleration Method Takeru Furukawa, Shunjiro Shinohara, Daisuke Kuwahara Helicon Plasma Thruster (HPT) can be a next generation electric thruster since highdense plasma can be generated with various operational parameters, and wear of plasma generation/acceleration grids (electrodes), which is typically seen in conventional electric thrusters, does not occur. We are conducting proposed, additional electrodeless plasma acceleration methods [1] to enhance the HPT performance e.g., Rotating Magnetic Field (RMF) plasma acceleration method [1,2]. Here, an azimuthal current can be driven in a plasma by the RMF application, and the plasma can be accelerated by an axial Lorentz force in the presence of a divergent magnetic field. The azimuthal current drive was demonstrated by the spatiotemporal measurements of the RMF. The acceleration effect becomes better by increasing an amplitude of ac current applied to the RMF antennas, leading to higher total thrust value. In this conference, current experimental results will be reported including above topics. [1] S. Shinohara \textit{et al}, \textit{IEEE Trans. on Plasma Sci}. \textbf{42} (2014) 1245. [2] T. Furukawa, \textit{et al}., \textit{Phys. Plasmas} \textbf{24} (2017) 043505, \textbf{26} (2019) 033505, AIP Adv. \textbf{7} (2017) 115204, and \textit{Rev. Sci. Instrum.} \textbf{89} (2018) 043505. [Preview Abstract] 

NP10.00102: Role of Neutral Gas Dynamics in Plasma Gun Devices William Riedel, Thomas Underwood, Mark Cappelli Neutral gas dynamics is described in plasma accelerators by considering the impact of the initial neutral gas distribution within the gun volume. A model based on the RankineHugoniot formulation in combustion is presented and used to predict both characteristic operating regimes observed experimentally. Precise neutral gas triggering is used to change the gas distribution within the accelerator and modify the initial conditions governing the breakdown process. Both bulk energy transfer and timeofflight measurements show that with increasing gas diffusion time, the directed energy in the flow decreases and the mode transitions from a deflagration to a snowplow mode. Neutral gas simulations indicate that neutral gas governs the transition between these operating modes. This informs strategies to maintain high acceleration efficiency in pulsed plasma accelerators and eliminate shocking conditions caused by higher gas loadings. [Preview Abstract] 

NP10.00103: Farfield CFD simulations of a magnetic nozzle on a fieldaligned mesh Thomas Marks, Benjamin Jorns, Iain Boyd Magnetic nozzles are space propulsion devices in which a plasma expands along diverging magnetic field lines, accelerating to produce thrust. Unless it at some point detaches, the plasma would follow the closed field lines of the nozzle, returning to the thruster and nullifying thrust. While it experimentally appears that detachment occurs in real devices, parts of this process remain poorly understood. For example, while it has been established that the heavier ions detach convergently (inward from the field lines), models predict the lighter electrons should detach divergently. This creates a current ambipolarity (CA) violation as electron and ions move in opposite directions. To explore if and how downstream current closure occurs and how it impacts thrust, there is a need to develop models with a larger experimental domain. The opensource CFD code SU2 was altered to model a magnetic nozzle, with all species treated as collisionless. A JamesonSchmidtTurkel scheme was employed for the fluxes, with a RungeKutta explicit scheme to advance time to steady state. The model confirms the presence of the downstream CA violation and shows that the resulting electric field pulls the ions outward and the electrons inward, increasing beam spread and decreasing thrust. [Preview Abstract] 
(Author Not Attending)

NP10.00104: A high efficiency resonant UHF plasma generator for electric propulsion Thiery Pierre A plasma generator is currently developed based on UHF ionization in xenon gas at reduced atmospheric pressure. The main characteristics is the use of a quarterwave wire resonator, consisting in a copper wire, 7 centimeters long, placed at a fixed distance (6 millimeters) over a copper ground plate. One end of the wire is grounded and the other end forms a small plate (5 x 5 millimeters) facing the grounded plate. The UHF excitation is made at a properly chosen distance from the grounded end of the wire. The resonance of the system is checked using a microwave network analyzer. A quality factor Q of about 200 is easily obtained. The excitation of the resonant system using a low power generator (about 5 watts CW) leads to the creation of an intense electric field in the interelectrode gap. The ionization is obtained routinely at a pressure of 0.5 atm. The system is applied to electric propulsion inserting a very high transparency stainless grid (80{\%} transparency) in order to extract ions from the miniplasma. The system is under development in order to optimize the ion flux extracted from the UHF generator. [Preview Abstract] 

NP10.00105: ABSTRACT WITHDRAWN 

NP10.00106: Twodimensional simulations of Electron Cyclotron Drift instability M. Jimenez, A. Smolyakov, O. Chapurin, T. Zintel, S. Janhunen, D. Sydorenko, Y. Raitses, I.D. Kaganovich The transverse (to the magnetic field) electric current due to ExB electron drift is a source of robust ElectronCyclotronDrift Instability (ECDI). It has been studied in the past in relation to the problem of anomalous resistivity in collisionless shock waves. Recently, it has attracted the interest as a possible source of anomalous transport in Hall thrusters. We have performed ParticleinCell simulation of this instability in twodimensions: the periodic ExB direction perpendicular to the magnetic field and the finite length direction along the magnetic field terminated by the metallic or dielectric walls. The electric field was externally applied and was fixed. The role of the boundaries, sheath losses and finite length (along the magnetic field) on the mode development and anomalous electron current were investigated. [Preview Abstract] 

NP10.00107: Analytical and numerical characterization of a one and twodimensional plasma photonic crystal with a sine series density perturbation W R Thomas, U Shumlak Plasma photonic crystals (PPCs) have the potential to significantly expand the capabilities of current microwave filtering and switching technologies by providing high speed ($\mu$s) control of energy bandgap/pass characteristics in the GHz through low THz range. While photonic crystals consisting of dielectric, semiconductor, and metallic matrices have seen thousands of articles published over the last several decades, plasmabased photonic crystals remain a relatively unexplored field. The majority of numerical and theoretical investigations into PPCs make the simplifying assumption of uniform density plasmas. In practice, most methods of generating repeatable, controllable plasmas have density gradients arising either from diffusion or wall effects. In this investigation we use analytical and numerical techniques on a plasmas perturbed with 1) a single sine wave, and 2) a finite Fourier series approximation of a square wave. These one and two dimensional PPCs will be studied to characterize their transmission properties and associated plasma dynamics, and establish relationships between dimensionless parameters (a lattice normalized plasma frequency, density perturbation ratio, density gradient) and bandgap frequency and width. [Preview Abstract] 

NP10.00108: Verification of LeastSquare Weighted Residual Methods for Solution of Global Model Equations Sergey Averkin, Thomas Jenkins In this work, we present a verification of a leastsquares weighted residual method that allows us to efficiently approximate solutions of plasma fluid equations. In this model we choose a rational functional representation with undetermined coefficients to represent various plasma properties. We then determine these coefficients such that the $L^2$ norm of the residual of 1D multifluid equations is minimized. Approximate plasma profiles can be obtained quickly and efficiently. In this work we focus on verification of the method by comparing our simulation results with analytical solutions of simplified fluid equations. We focus on cylindrical plasma discharges in a wide range of pressure regimes, without the heuristic approximations used by conventional global models. We also discuss the optimal order of polynomials used in our rational function representation relative to desired accuracy constraints, and quantify the error in our functional approximations. [Preview Abstract] 

NP10.00109: Synthesis of High or Low Melting Point Metallic Thin Films Utilizing Magnetized Coaxial Plasma Guns Saiga Yaegashi, Kaoru Suzuki, Kenichi Matsuda, Satoshi Kurumi, Tomohiko Asai, Junichi Sekiguchi, Daichi Kobayashi Recently, thermoelectric materials are of interest for applications as heat pumps and power generators. The Heuslertype intermetallic compound has received intense attention because of a large enhancement in the Seebeck coefficient by alloying high melting point transition metal (Ti, V, Fe) and low melting point paramagnetic metal (Al). In this study, we have attempted to develop a deposition system equipped with multisource magnetized coaxialplasma guns (MCPGs) for depositing materials having different melting points independently. The MCPGs is mainly consisted of a center rodshaped target as a cathode electrode, an outer ringshaped target as an anode electrode, and the pulsedcurrent generator. Argon gas was introduced into the chamber (1 Pa) as a working gas. DC voltages (1.5\textasciitilde 3.5 kV) were charged to a capacitor (400 µF) and then discharged (peak current: 10\textasciitilde 70 kA) between Al and Fe targets utilizing a rectifier (Ignitron, National, NL7703). They were accelerated by the Lorentz force due to high discharge current and ejected to a glass substrate. Al or Fe thin films were obtained on the substrate on which the plumes were deposited. [Preview Abstract] 

NP10.00110: Deconvolution of a Plasma Pulse Signal by use of the HilbertHuang Transform James Henderson, Dereth Drake The HilbertHuang Transform uses the method of empirical mode decomposition in which a signal is decomposed into multiple signals called intrinsic mode functions (IMFs). A Hilbert Transform is then applied to these functions in order to obtain instantaneous frequency data. This results in a time dependent distribution of signal amplitudes, known as the Hilbert Spectrum. By applying this transform to a complex or noisy signal, the noise can be isolated and removed from the signal source. This allows for a much cleaner, easier to study signal. In this poster, we will describe the theory behind this technique and demonstrate how it can be used to study the plasma pulse from a commercial plasma system. [Preview Abstract] 

NP10.00111: Selfconsistent model for ultrashort laserpulse propagation and quantum kinetics of electronhole plasmas in quantum wires Jeremy Gulley, Danhong Huang We present a quantumkinetic model for strong coupling between ultrashort laser pulses and the carrierscattering dynamics and nonlinear transport of photoexcited electronhole plasmas in semiconductor nanowires. These lowtemperature plasmas are further driven by an applied DC electric field along the wires, including resistive forces for momentum relaxation due to Coulomb scattering and collisions with the lattice. Simulations solving this strongcoupling model allow us to study the correlation between the localized plasma response of quantum wires and the spatialtemporal features and phases of the scattered light pulses. The model also makes it possible to reveal a unique correlation between the DC current from the driven electronhole plasma and the localized longitudinal electromagnetic field due to induced longlasting plasma oscillations in the quantum wires. [Preview Abstract] 

NP10.00112: Validated modeling of twodimensional effects in carbon arcs. Jian Chen, Alex Khrabry, Andrei Khodak, Igor Kaganovich, Yevgeny Raitses Short atmosphericpressure arcs with ablating carbon anode are used for production of carbon nanoparticles. Comprehensive experimental study was recently performed using set of insitu diagnostics [1]. Many arc parameters, such as the arc current and interelectrode gap width, can significantly affect the carbon ablation rate and, consequently, the production of nanoparticles. In this work, we employed a previously developed selfconsistent model [2] to study plasma properties of the short carbon arc in helium atmosphere. Temperature profiles were determined from the heat balance equations which accounts for radiation, electron emission, recombination of ions, spacecharge sheaths and joule heating. A sheath model was used as an effective boundary condition for transport equations to determine the sheath voltage drop and particle fluxes on the electrodes. This model was implemented into ANSYS CFX code [2]. Results show that part of carbon ablated from anode center can return back to anode periphery; and current flows nonuniformly from a spot at anode; and the spot size increases with the arc current. \textbf{References} [1] V. Vekselman, \textit{et al.,} PSST \textbf{26}, 065019 (2017). Additional references are available at \underline {nano.pppl.gov} [2] A. Khrabry, \textit{et al.} \underline {https://arxiv.org/abs/1902.09991}. [Preview Abstract] 

NP10.00113: Measurements of electric potential in the carbon arc Nirbhav Chopra, Yevgeny Raitses In an anodic carbon arc discharge for synthesis of nanomaterials, carbon material is introduced into the arc by the ablation of the graphite anode. Characterizing the anode ablation is important for understanding of the formation of carbon nanomaterials (e.g. carbon nanotubes) in the arc [1]. Anode ablation depends on the power balance at the anode, which is influenced by whether the anode sheath is electronrepelling (negative anode sheath) or electronattracting (positive anode sheath) [2]. In this work, we study the spatial distribution of the electric potential in the arc. To measure the electric potential, a fast swinging Langmuir probe was developed and used. The floating potential of the probe is measured, from which the plasma potential is estimated. The dependence of the electric potential distribution on the arc current will be discussed. [1] J. Fetterman, Y. Raitses, and M. Keidar, ``Enhanced ablation of small anodes in a carbon nanotube arc plasma'', \textit{Carbon }46$,$ 1322 \textit{(2008).} [2] V. Nemchinsky and Y. Raitses, ``Anode sheath transition in an anodic arc for synthesis of nanomaterials'', \textit{Plasma Sources Sci. T.} 25, 035003 \textit{(2016)}. [Preview Abstract] 

NP10.00114: Electrical and optical characterization of a cold atmospheric pressure plasma jet in the ambient air Veda Prakash Gajula, Narayan Behera, Kiran Patel, Ajai Kumar A lowcost atmospheric pressure plasma source with helium (He) as active gas has been developed keeping in view of a wide range of biomedical applications. For these applications, optimization of plasma parameters such as electron density, electron excitation temperature, gas temperature, active species, the active area of the plume, etc. are required for which critical characterization plasma plume is essential. In order to understand above, a lowtemperature atmospheric pressure plasma source with helium (He) as an active gas is developed. 4 kVpp, 33 kHz sinusoidal voltage is used to produce plasma jet. Helium gas with flow rates of up to 11 liters per minute is used to produce plasma plume of around 4 cm length into the ambient air. Thorough characterization of the plume has been carried out by using electrical and optical diagnostics. Voltage and current probes are used for understanding the electrical discharge behavior with applied voltage and gas flow whereas emission spectra measurements, ICCD imaging are used for estimating the parameters of plasma such as electron excitation temperature, electron density. The plasma density along the length of the plasma plume has been assessed and the values are in the range of 0.053.2 x 10$^{\mathrm{12}}$ cm$^{\mathrm{3}}$. [Preview Abstract] 

NP10.00115: Optical emission diagnostics and modeling of H$_{\mathrm{2}}$rich microwave plasmas containing B$_{\mathrm{2}}$H$_{\mathrm{6}}$. Nicholas Arnold, Kollal Chakrabarty, Stuart Loch, Aaron Catledge Inprocess control of the local plasma environment during microwave plasma chemical vapor deposition is important in predicting coating structure and properties. In this regard, an understanding of the plasma characteristics such as gas temperature, column density, and populations of collisionally excited species as well as their dependence on deposition conditions such as microwave power, chamber pressure, and feedgas concentrations is needed. In this study, we use optical emission spectroscopy in conjunction with collisionalradiative and LTE models to investigate these aspects for H$_{\mathrm{2}}$rich plasmas with/without small admixtures of diborane (B$_{\mathrm{2}}$H$_{\mathrm{6}})$ and ammonia (NH$_{\mathrm{3}})$ associated with growth of boron nitride films. [Preview Abstract] 

NP10.00116: Development of inverter power supply for microplasma emission source on Micro Total Analysis System for multi\textunderscore elemental analysis Mayuko Yoshida, Yuma Suenaga, Motohide Aoki, Tomonari Umemura, Akitoshi Okino Recently, Micro Total Analysis System ($\mu $TAS) has attracted attention as a compact device for not only chemical reactions but also chemical analysis. For analysis of microvolume sample, high sensitive and small detectors on $\mu $TAS is required. For elemental analysis we have developed a microplasma emission source that has diameter of 500 $\mu $m using a dielectric barrier discharge plasma on a microchip. By the atomic emission source, halogen gases of subppm order was successfully analyzed. For more sensitive analysis, it is necessary to set the optimal discharge conditions which depend on the target elements. In this study, we developed an inverter power supply for a microplasma emission source that can generate plasmas with multiple discharge conditions continuously. The power supply can instantaneously and arbitrarily change the voltage, the frequency, and the wave form. Therefore, the power supply may continuously generate plasma with the optimal conditions corresponding to the respective elements. Basic characteristics of the plasma generated by the power supply was measured by timeresolved spectroscopy. In the presentation, details of the power supply and the measured results will be presented. [Preview Abstract] 

NP10.00117: Development of Plasma Fine Bubbles Generator to Improve Water Quality Utilized by Barrier Discharge. Wataru Takahashi, Satoshi Kurumi, Kenichi Matsuda, Kaoru Suzuki Techniques for generating nano, microscale bubbles (or fine bubbles) have been attracted for improving water quality as an environmentallyconscious method. Natural bubbles in water are affected by their own buoyant forces, so they behave to be floated toward the water surfaces. For the case of fine bubbles (FBs, for short), they have been affected by surface charges on the bubbles in addition to the buoyant force. Therefore, the FBs repulse each other like electrostatic forces, and they also stable in water when the forces are much greater than the buoyant one. In our previous study, homemade generators of FBs have been developed to the application for decomposing hazardous contaminations in polluted waters by FB's negative charges. However, we are incapable of obtaining good effects for water quality improvement utilizing this system so far. In order to progress our research, we have tried to install barrier discharge systems into the FB generators so as to let the bubble have plasma particles and ozone. The plasma FBs (pFBs) containing ozone would be expected to enhance the ability for waterquality improvement. In this study, we have investigated a new equipment of the pFBs generator and behaviors of the FBs in water. [Preview Abstract] 
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