Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Plasma Physics
Volume 66, Number 13
Monday–Friday, November 8–12, 2021; Pittsburgh, PA
Session ZP11: Poster Session IX: Supplemental
Poster
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Room: Hall A |
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ZP11.00001: Using Dante, radiography, and spectral temperature diagnostics to constrain simulations of the COAX radiative shock experiment Shane X Coffing, Chris Fryer, Suzannah R Wood, Chris J Fontes, Harry F Robey, Pawel M Kozlowski, Heather M Johns, Todd Urbatsch In a growing number of radiative shock tube experiments, a laser irradiates a hohlraum to drive a radiation wave into a foam tube and subsequently develop a radiative shock. Simulating these experiments requires careful modeling choices and approximations, and comparing simulations to diagnostic data leads to an often parameterized model that can be exploited to constrain key physics in the experiment. The experimental platform COAX is designed to constrain numerical models of a such a radiative shock by employing radiography for spatial and shock information, Dante diagnostics for characterizing the hohlraum drive, and a novel spectral diagnostic designed to probe the temperature gradient of the wave. Using parameterized 2D simulations with a hohlraum-laser modeling package, we analyze the drive, shock position and curvature, and temperature via synthetic spectra of the radiative shock and discuss how we propagate uncertainties to our physical understanding of the experiment. |
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ZP11.00002: Predictive Modeling For An Inductively Coupled Plasma Generator Graeson Griffin, Jens Schmidt, Georg Herdrich, Lorin S Matthews, Calvin Carmichael, Parker J Adamson, Truell W Hyde The study of high enthalpy plasma flows in a vacuum has applications in space, atmospheric, and fusion physics. Through a partnership between the Center for Space Physics, Astrophysics, and Engineering Research (CASPER) and the Institute of Space Systems at the University of Stuttgart (IRS), Baylor University has developed an inductively heated plasma generator (IPG-6B). As part of an ongoing research project, an extended range of operating parameters for the current configuration of the IPG6-B is now being utilized. Under these extreme conditions, problems that were once minimal, for example, thermal expansion and arcing, have become exaggerated. As a result, experiments have entered an unsustainable "burn then crash" cycle. In order to move forward, a technique to predict these failures is necessary. This poster will present preliminary findings from a SolidWorks simulation of the IPG-6B and data allowing comparison of these findings to Pitot Probe, Langmuir Probe, and Calorimeter data collected from the machine. |
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ZP11.00003: Adaptive Workflow for Simulation of Cold Plasma in RF Heaters Morteza Hakimi Siboni, Mark S Shephard This poster will describe a workflow for the execution of adaptive high-performance simulations of RF fusion systems. In this workflow, the simulation input consists of a CAD model attributed with the needed analysis attributes. The analysis mesh is automatically generated and the analysis steps are executed using the time-harmonic Maxwell's equations using MFEM libraries. A patch recovery-based error estimator is used to drive a conforming mesh adaptation procedure using PUMI mesh adapt libraries. |
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ZP11.00004: Laser ion acceleration from tailored solid targets with micron-scale channels Kirill Lezhnin, Sergei V Bulanov Laser ion acceleration is a promising concept for generation of fast ions using a compact laser-solid interaction setup. In our study, we theoretically investigate the feasibility of ion acceleration from the interaction of petawatt-scale laser pulses with a structured target that embodies a micron-scale channel filled with relativistically transparent plasma. Using 2D and 3D Particle-In-Cell (PIC) simulations and theoretical estimates, we show that it is possible to generate GeV-level protons with a monoenergetic-like feature in the proton energy spectrum. We attribute the acceleration mechanism to a combination of Target Normal Sheath Acceleration and Radiation Pressure Acceleration. Optimal parameters of the target are formulated theoretically and verified using 2D PIC simulations. 3D PIC simulations with the realistic laser pulse and target parameters show the feasibility of presented laser ion acceleration scheme for currently available petawatt laser facilities. |
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ZP11.00005: Modeling Gamma-Ray and Pair Creation by Ultra-intense Lasers irradiating Large High-Z Targets Edison P Liang, Scott Wilks, Joohwan Kim In a series of laser experiments by the Rice-UT collaboartion using the Texas Petawatt Laser to irradiate cm-sized Au and Pt targets at intensities exceeding 10^21 Wcm^-2, we observed a number of intriguing and surprising results. These include the observation that within a broad solid angle lying between laser forward and target normal directions, the ratio of emergent positrons to electrons can greatly exceed unity. Electron emission appears to be strongly suppressed by intense electromagnetic fields which are angle dependent. At the same time the hot electron spectrum and gamma-rays spectrum both exhibit unusual properties. Here we present some preliminary resutls of modeling hot electron transport in these large high-Z solid targets by incorporating self-consistent electronmagnetic fields. |
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ZP11.00006: Civilization needs abundant sustainable energy – Fusion breeding may be best Wallace M Manheimer In a mid-century world with 10 billion people, each person will demand a middle class life style, namely a lifestyle which uses about the same power per capita, 5kW, as the citizens of the OECD countries. Hence the total world power should be 40-50 TW, depending on how much the efficiency of energy use increases between now and mid-century. In other words, at least triple the energy of what is used now, will be needed. While non-sustainable sources (i.e. hydrocarbons and mined 235U) can support this lifestyle, for a while, these sources will be depleted in 1/3 the time estimated on the basis of today’s use. While solar and wind are certainly sustainable, this paper makes the case that they cannot produce nearly the required power at anything like an economic price. Pure fusion almost certainly cannot either, at least in this century. The inescapable conclusion is that breeding nuclear fuel is the only option. Either fission or fusion can be used to breed fissile material. This paper makes the case that despite the head start fission breeding has, fusion breeding is ultimately the best choice. One fusion breeder can fuel at least 5 thermal reactors of equal power. It takes two fission breeders at maximum breeding rate to fuel one. Fusion breeding can be a key part of what this author has called ‘The Energy Park”, a power infrastructure that is economically and environmentally viable and has virtually no proliferation risk. |
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ZP11.00007: Optically Switchable MeV Ion/Electron Accelerator Itamar Cohen, Yonatan Gershuni, Michal Elkind, Guy Azouz, Assaf Levanon, Ishay Pomerantz The versatility of laser accelerators in generating particle beams of various types is often promoted as a key applicative advantage. These multiple types of particles, however, are generated on vastly different irradiation setups, so that switching from one type to another involves substantial mechanical changes. |
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ZP11.00008: Modeling ICRF mode conversion in VSim with a kinetics-only delta-f (KODF) method Thomas G Jenkins, David N Smithe We present a new delta-f PIC method, kinetics-only delta-f (KODF), for modeling the nonlinear phase space evolution of plasma species distribution functions. Conventional delta-f methods evolve computational markers along characteristic trajectories to model perturbations around a known equilibrium distribution, with a marker weight variable tracking deviations of the distribution function from equilibrium. In KODF, we generalize this concept to incorporate cold linear plasma waves into the known (quasi)analytic plasma behavior. Perturbations modeled by KODF methods are thus nonlinear, finite-temperature perturbations (modeled with PIC) atop an equilibrium and its associated cold linear waves (which can each be modeled analytically or numerically without PIC noise). We demonstrate an implementation of KODF in the VSim code. VSim's semi-implicit FDTD methods [Smithe, PoP 14, 056104 (2007)] are used to model the fluid behavior of cold plasma waves; source terms arising from these waves (e.g. from gradients of cold current/charge densities) concurrently drive and evolve responsive warm plasma effects in a PIC formulation. We explore the noise-reduction capabilities of the KODF algorithm and its ability to model waves of interest in RF heating scenarios (e.g. mode-converted IBWs). |
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ZP11.00009: Time dependent Equilibrium Reconstruction in LTX_B Leonid Zakharov The conventional equilibrium reconstruction represents a time slice of measurements |
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ZP11.00010: The Auger electron therapy of cancer driven by mono-energetic X-rays with the vector nanoparticles loaded with Iodine Yuya Higashi, Kotaro Matsumoto, Ayumi Shiro, Yue Ma, Mathilde Laird, Shanmugavel Chinnathambi, Albane Birault, Tan Le Hoang Doan, Ryo Yasuda, Tetsuya Kawachi, Fuyuhiko Tamanoi, Toshiki Tajima, Ernesto Barraza-Valdez Irradiation of high Z elements with monoenergetic X-rays causes photoelectric effects that include the release of Auger electrons. These electrons have strong DNA damaging effects including double strand DNA cleavage. This approach has been explored as a potential cancer therapy (the Auger therapy). We first developed gadolinium loaded mesoporous silica nanoparticles (Gd-MSN) and demonstrated their ability to destroy tumor spheroids upon irradiation with synchrotron generated (SG) monochromatic X-rays of 50.25 keV. We now tried Iodine with a K-edge energy of 33.2 keV. We show that the destruction was dependent on the presence of iodine and that the destruction effect is highly dependent on monochromatic X-ray energy. Results of experiments using three different energy levels (33.0, 33.2 and 33.4 keV) demonstrated that spheroid destruction, apoptosis induction and double strand DNA breaks occurred with the 33.2 keV X-ray irradiation, but not with 33.0 keV irradiation and less with 33.4 keV irradiation. |
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ZP11.00011: Neural Dynamical Systems: Balancing Structure and Flexibility in Physical Prediction Viraj Mehta, Ian Char, Willie Neiswanger, Youngseog Chung, Andrew O Nelson, Mark D Boyer, Egemen Kolemen, Jeff Schneider Modelling the dynamics of plasma is difficult and important for many applications including controlled fusion. We introduce Neural Dynamical Systems (NDS), a method of learning dynamical models in various gray-box settings which incorporates prior knowledge in the form of systems of ordinary differential equations. NDS uses neural networks to estimate free parameters of the system, predicts residual terms, and numerically integrates over time to predict future states. A key insight is that many real dynamical systems of interest, including plasmas, are hard to model as the dynamics may vary across rollouts. We mitigate this problem by taking a trajectory of prior states as the input to NDS and train it to dynamically estimate system parameters using the preceding trajectory. |
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ZP11.00012: Description of longitudinal space charge effects in beams and plasma through dielectric permittivity Nikolai Yampolsky, Kip Bishofberger We develop a universal framework which allows quickly solve a wide class of problems for longitudinal space charge effects in beams and plasmas in cylindrical geometry. We introduce the longitudinal dielectric permittivity for the beam of charged particles, which describes its collective space charge response. The analysis yields an effective plasma frequency, which depends on the transverse geometry of the system. This dielectric permittivity mirrors the dielectric permittivity of plasma and matches the one dimensional (1D) expression once the transverse size of the beam is large. Several particle species can be included as additive terms describing susceptibility of each specie. The developed approach allows to study stability criteria for collective beam-beam and beam-plasma instabilities for arbitrary transverse distributions in particle densities. |
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ZP11.00013: Longitudinal diagnostics of ultra-short relativistic electron bunches based on coherent undulator radiation Nikolai Yampolsky, Bricker Ostler, Claudio Emma, Heather L Andrews, Muhammed Zuboraj, Quinn Marksteiner, Samuel Barber, Fumika Isono, Robert D Ryne, Jeroen van Tilborg Time resolved diagnostics of current profile in relativistic electron bunch is a challenging task. It is particular challenging to diagnose ultra-short electron bunches produced in plasma wakefield accelerators. The bunch length is on the order of a femtosecond, which cannot be measured with existing techniques. We report development of the longitudinal time resolved diagnostics based on coherent undulator radiation. Coherent undulator radiation results in the signal, which power spectral density is proportional to the one of the bunch current profile. Measurement of the power spectral density of coherent radiation is simplified in case of undulator radiation since different frequencies are emitted at different angles and they are directly measured on a single detector downstream. The temporal profile of the electron bunch current is reconstructed from the spectral data. Here we report start-to-end analysis of the proposed diagnostics and demonstrate its feasibility for diagnosing ultrashort LWFA bunches. |
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ZP11.00014: Investigating ELM Pacing by Vertical Oscillations on DIII-D Dario Panici, Andrew O Nelson, Egemen Kolemen, Florian M. Laggner Edge Localized Modes (ELMs) have been observed to be triggered by fast vertical oscillations of the plasma on multiple tokamak devices. These vertical plasma oscillations have been considered as a possible alternative ELM pacing mechanism for future fusion reactors. This work presents analysis of a DIII-D shot with vertical plasma oscillations. Shot analysis will be shown, in an attempt to determine if ELM pacing was achieved. Stability analysis performed during the course of the oscillations will also be presented. |
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ZP11.00015: A first-principles study of surface stability and H behavior near surfaces of W borides Li Yang, Brian D Wirth Understanding the behavior of tungsten boride (WxBy) surfaces in a fusion reactor environment is necessary since WxBy may form on W divertor surfaces due to boronization treatments. The surface stability of WxBy (I41/amd-WB, P63/mmc-WB2 and I4/m-W2B) with low-index orientations, as well as hydrogen (H) energetics near WxBy surfaces has been investigated by density functional theory calculations. For single element terminated WxBy surfaces, B terminated surfaces are more stable than W terminated due to the significant reconstruction of B. The H surface adsorption energy and activation energy of H diffusion penetration below WxBy surfaces are mainly related to the outermost termination of surfaces. Specifically, the WB(001) surface terminated with two B layers, referred to as WB(001)-TBB, has higher H adsorption ability and lower H diffusion probability on the surface than other terminations, which results from the significant charge transfer from B to H. However, B atoms on the WB2(0001)-TBB surface decrease both H adsorption and diffusion abilities on the surface, but enhance H diffusion below the surface in comparison to the W terminated WB2(0001) surface. H would be trapped and diffuse within atomic surface gaps on the WB2(2-1-10) surface, while H below the surface layer would jump along the [0001] direction rather than diffuse into bulk. The surface diffusion activation energy of H on the W2B(001) surface varies only slightly with the termination. Once H crosses the surface layer of W2B(001) with either termination, H prefers to diffuse into the bulk. Correspondingly, we predict that both WB2(0001) and WB2(2-1-10) surfaces likely have higher H retention than other evaluated WxBy surfaces. |
Not Participating |
ZP11.00016: Post-mortem surface chemistry analysis of boronized graphite PFC samples and their links to PMI behavior in NSTX-U Camila Lopez Perez, Hanna Schamis, Jean Paul Allain In the 2015-2016 experimental campaign the National Spherical Torus Experiment Upgrade (NSTX-U) used ATJ -graphite as a first wall and divertor material. Wall conditioning was completed with deuterated trimethylboron (d-TMB). Post-mortem samples taken from graphite tiles extracted from various locations in the NSTX-U divertor region after the campaign were analyzed at the IGNIS (Ion-Gas-Neutral Interactions with Surfaces) facility at UIUC using X-ray Photoelectron Spectroscopy (XPS). According to the XPS analysis, samples contain on average 15-30% B. At Penn State, additional post-mortem samples are analyzed using both XPS and Scanning Auger Electron Spectroscopy (AES) to establish an elemental mapping and chemical characterization of the extracted tiles. In addition, samples of varying B concentration will then be exposed to high flux D+ ions, mimicking plasma material interactions in a tokamak, and later analyzed with XPS and Thermal Desorption Spectroscopy (TDS) to decipher PMI behavior linked to NSTX-U plasma operation. XPS and TDS will also be used to investigate the effects of the D+ irradiation on the surface chemistry and retention of the samples. The acquisition of data through XPS, AES and TDS will further investigate the chemical composition of the tiles after deuterium exposure. |
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ZP11.00017: Understanding of Liquid Lithium Wettability in Porous Tungsten Fusion Plasma Facing Components Sara Kolecki, JP Allain, Camilo Jaramillo, Martin Nieto-Pérez, Matthew S Parsons, Camila López Pérez, Carli S Smith Exposure of solid plasma-facing components (PFCs) to high irradiation conditions in fusion reactors leads to significant erosion and re-deposition under high-duty cycle conditions. High heat and particle flux can also undermine structural properties of PFCs such as fracture strength and creep rate. Liquid metal (LM) PFCs may be a practical alternative due to their ability to continually replenish material. Their finite residence time helps them tolerate both steady-state and transient heat fluxes within fusion reactors. However, the generation of thin liquid films of low-Z materials has been difficult due to poor adhesion and high surface tension. The work presented here explores the use of nano- and meso-porous substrates as an alternative to improve wetting using capillarity-driven effects such as: imbibition, percolation and wicking. Liquid lithium will be applied to tungsten substrates fabricated by atmospheric plasma spray and field-assisted/spark plasma sintering with an in-vacuo lithium dropper in the IGNIS-2 facility at Penn State's Radiation Surface Science and Engineering Lab. Wettability of liquid Li and porous tungsten samples will be imaged and video recorded in-situ at surface temperatures up to 400 C. Wetting angles will be measured to determine which tungsten substrates and surface microstructures are the most wettable by Liquid Li coatings. |
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ZP11.00018: Effect of ion acoustic instabilities on the energy-angle distributions of the ions impacting on the wall of a finite-size plasma Md Fazlul Huq, Mohammad Mustafa, Logan Meredith, Davide Curreli In this work, we have numerically investigated the effect of ion acoustic instabilities on the energy-angle distributions of the ions impacting on the wall of a finite-size plasma. Ion acoustic instabilities develop in non-equilibrium plasmas having electron temperature much larger than the ion temperature. As revealed by a dispersion analysis, this instability is also affected by the drift motion of the ions, normally encountered in the sheath and presheath of a finite-size plasma interfaced with a material wall. The analysis was performed using the hPIC Particle-in-Cell code. Simulations show that at large temperature ratios the ion distribution develops a high-energy tail triggered by finite-amplitude acoustic waves. The instability has the net effect of increasing the ion impact energy on the walls above the expected thermal ranges, and of reducing the ion pitch angle at the time of impact. A systematic parametric analysis as a function of the temperature ratio is reported, showing the gradual onset of the instability and its effect on the energetic tails of the distributions. |
Not Participating |
ZP11.00019: Surface chemistry and morphology studies of boronized tungsten samples from WEST Hanna Schamis, Camila Lopez Perez, Jean Paul Allain WEST is a long-pulse tokamak with a full tungsten first wall and divertor which are conditioned using boron. After the C4 campaign, tiles were extracted from the tokamak in order to perform post-mortem analyses. The analyses will be performed at Penn State with techniques such as depth-profile X-ray Photoelectron Spectroscopy (XPS), Scanning Auger Electron Spectroscopy, Scanning Electron Microscopy, and 3D optical profilometry. With XPS, the chemical composition and stoichiometry of the top 10 nm of a material can be analyzed, while depth profiling enables characterization of compositions from the surface towards the bulk of the material. The focus of these post-mortem analyses will be on characterizing the chemistry and morphology of reconstituted (or redeposited) layers. Reconstituted layers form after repeated high particle and heat flux exposure in tokamak environments. The characteristics of these WEST reconstituted layers will be compared to those of lab-grown boron and tungsten mixed material deposited films, in order to evaluate new ways to study these complex materials. These mixed material films will be deposited and characterized in the new IGNIS-2 facility at Penn State. |
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ZP11.00020: Development of a reduced model for energetic particle transport by sawteeth in tokamaks Mario L Podesta, Marina Gorelenkova, Nikolai Gorelenkov, Roscoe B White, Phillip J Bonofiglo, Francesca M Poli, Anna Teplukhina, James J Yang, Marco Cecconello, Matteo Vallar Sawteeth are known for inducing transport and loss of energetic particles (EP), and for generating seed magnetic islands that can trigger tearing modes. Both effects degrade the plasma performance. Several theories and numerical models have been previously developed to quantify EP transport by sawteeth, with various degrees of sophistication to differentiate the response of EPs at different energies and on different orbits. The analysis is frequently limited to a single time slice. This work describes the development and initial benchmark of a framework that enables a reduced model for EP transport by sawteeth retaining the full EP phase-space information. Mode properties used in the model are consistent with the ideal MHD m/n=1/1 structure from NOVA. The model, implemented in the ORBIT particle-following code, can be used either as a stand-alone post-processor taking input data from TRANSP, or as a pre-processor to compute transport coefficients that can be fed back to TRANSP for time-dependent simulations. The advantage of the latter approach is that it enables an accurate modeling of sources, sinks and overall transport properties of EP and thermal plasma species for comprehensive studies that require detailed information of the fast ion distribution evolution over time. |
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ZP11.00021: Implementation and benchmarking of improved atom and molecule neutral fluid models in UEDGE Menglong Zhao, Thomas D Rognlien, Andreas M Holm, Marvin E Rensink, Maxim V Umansky, George J Wilkie Fluid neutral model is regularly used in UEDGE to simulate neutral transport. For high |
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ZP11.00022: The crutial role of the rotating magnetic field in the formation of field reversed configuration Wenqiu Li Understanding the penetration process of rotating magnetic field (RMF) driven by odd-parity RMF (RMFo) antenna may fundamentally enable us to comprehend the heating mechanism of RMF driven field-reversed configuration (FRC), and further allow us to achieve long time (>a few hundreds of milliseconds) FRC maintenance. Choosing parameters related to the PFRC-2 experiment, with wall radius of 5 cm, axial static magnetic field of 300 G, magnetic field induced by the RMF antenna of 12 G, RMF frequency of 4 MHz, RMF antenna current of 1000 A, plasma density of 1013 cm-3, and electron temperature of 200 eV, full multiphysics particle-field interaction simulations imply that the FRC is formed after 10 RMF periods, and the azimuthal electric field is responsible for accelerating electrons and gradually penetrating the core plasma region; on the other hand, when a higher RMF magnetic field ( 30 G) is applied, the azimuthal plasma current induced by RMF becomes penetrating in a non-azimuthally symmetrical form, as if the azimuthal plasma current drives spiral field penetration. |
Not Participating |
ZP11.00023: X-ray diffraction from supercooled liquid hydrogen and deuterium mixtures Christopher Schoenwaelder, Luke Fletcher, Siegfried Glenzer The nucleation and growth of metastable structures in supercooled liquids is a mostly unexplored phenomenon in condensed matter physics. Moreover, the study of supercooled isotopic mixtures, and the expected phase separation during crystallization, remains an experimental challenge due to the fast timescales and atomic level length scale changes. High rep-rate ultra-fast X-ray diffraction with high peak brightness in combination with a liquid microjet is an effective method to dynamically probe the crystallization processes experimentally [1-4]. These cryogenic jet targets are created by liquefying an ultra-high purity gas in a copper assembly cooled down to cryogenic temperatures. The liquid is continuously injected into a vacuum chamber through a micron-sized aperture, where it rapidly solidifies via evaporative cooling [3]. Since cryogenic jets are not limited to a single sample gas it presents an ideal target for studying crystallization processes of isotopic, or binary, liquid mixtures with microscopic precision. Here, we report the first comprehensive time resolved observations of liquid hydrogen and deuterium mixtures, supercooled to temperatures below the melting point using X-ray diffraction from the Linac Coherent Light Source (LCLS).
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ZP11.00024: Plasma-Density Imaging using a 2-Dimensional, SecondHarmonic, Dispersion Interferometer Frank J Wessel, Cameron T Chavez, Andrew Egly Optical interferometers used for plasma-density measurements are typically robustly mounted, two-arm, highcost, high-maintenance installations. The Second-Harmonic Dispersion Interferometer (SHDI) is an important departure, utilizing a common-path laser beam that is frequency doubled before, and after, the plasma sample. This configuration allows the dispersive-phase shift between the SH beams to be measured in a simple, low-cost, low-maintenance system. |
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