Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session TO06: Magnetized High-energy-density PlasmaLive Streamed
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Chair: Alla Safronova, UNR Room: Ballroom 111 C |
Thursday, October 20, 2022 9:30AM - 9:42AM |
TO06.00001: Simulations of the MARZ (Magnetically Ablated Reconnection on Z) platform Jack D Hare, Rishabh Datta, Jeremy P Chittenden, Aidan C Crilly, William R Fox, Jack W Halliday, Christopher A Jennings, Hantao Ji, Carolyn C Kuranz, Sergey V Lebedev, Dmitri A Uzdensky, Katherine Chandler, Clayton E Myers In extreme astrophysical environments, such as black hole coronae and pulsars, magnetic reconnection proceeds alongside strong radiative cooling, which modifies the energy partition and pressure balance within the reconnection layer, and may trigger cooling instabilities. Through the Z Fundamental Science Program (ZFSP), the MARZ (Magnetically Ablated Reconnection on Z) collaboration was awarded four shots on Z in FY22-23 in order to study radiatively cooled magnetic reconnection driven by the Z Machine at Sandia National Laboratories*, the world’s largest pulsed-power facility. |
Thursday, October 20, 2022 9:42AM - 9:54AM |
TO06.00002: Plasma flows from dual exploding wire arrays for the MARZ campaign on Z Rishabh Datta, Jeremy P Chittenden, Aidan C Crilly, William R Fox, Jack W Halliday, Christopher A Jennings, Hantao Ji, Carolyn C Kuranz, Raul F Melean, Sergey V Lebedev, Dmitri A Uzdensky, Clayton E Myers, Katherine Chandler, Jack D Hare We characterize the plasma outflows generated by a dual inverse wire array load on the Z machine (Sandia National Laboratories). The MARZ (Magnetically Ablated Reconnection on Z*) campaign uses two identical 40 mm diameter, 40 mm tall exploding wire arrays with 150, 75 m diameter Aluminum wires, driven in parallel by a 20 MA, 300 ns rise time current pulse. 3D simulations with the two-temperature resistive MHD code Gorgon were used to design the arrays that would continuously ablate plasma from the wire surface to generate radially-diverging, supersonic (MS > 5) and super-Alfvénic (MA ~ 2) magnetized plasma outflows with frozen-in magnetic flux (RM ~ 100). Anti-parallel magnetic fields advected by the outflows collide at the mid-plane to create a reconnection layer, which is used to study radiatively-cooled reconnection for the MARZ experimental campaign. |
Thursday, October 20, 2022 9:54AM - 10:06AM |
TO06.00003: Experimental study of semi-relativistic quasi-perpendicular shock formation Brandon K Russell, Paul T Campbell, Chuanfei Dong, Gennady Fiksel, Philip M Nilson, Alexander G Thomas, Christopher A Walsh, Karl M Krushelnick, Louise Willingale Laboratory studies of microphysics with strong magnetization and relativistic flow velocities may provide insight into extreme astrophysical phenomena. This work studied an asymmetric interaction on the OMEGA EP laser system, by focusing a long pulse laser to ~1014 W/cm2 at a small separation from a relativistic intensity >1019 W/cm2 short pulse laser on a CH foil. A modification of the quasi-static magnetic fields of the long-pulse generated plasma plume is observed in target-normal proton radiographs. Forward modeling shows that this modification is evidence for magnetized shock formation. A 3D OSIRIS particle-in-cell simulation shows that the strong self-generated magnetic fields of the short-pulse plasma drape around the long-pulse plasma plume, forming an unstable contact discontinuity from which a shock is driven. |
Thursday, October 20, 2022 10:06AM - 10:18AM |
TO06.00004: Relativistic laser perturbation to laser-driven magnetic reconnection Joshua Latham, Brandon K Russell, Louise Willingale, Paul T Campbell, Gennady Fiksel, Philip M Nilson, Karl M Krushelnick Experiments which measure the magnetic fields laser-driven plasmas give insight into the basic processes of plasmas such as magnetic reconnection. These processes become more difficult to describe when there is a mixture between regimes, such as between relativistic kinetic plasma and MHD-describable plasma, as in this case. In this experiment, a 10-ps, 10^19 W/cm^2 laser impinged on the interface between two plasma plumes driven by 2.5 ns, 10^14 W/cm^2 lasers at the OMEGA-EP laser facility. The magnetic fields were measured with proton radiography from a TNSA source. In one regime, the relativistic perturbation inhibited the magnetic reconnection between the two plasma plumes, but with a different timing of the relativistic laser the reconnection may have been enhanced. Probable causes will be discussed. This work is relevant to understanding the physics of reconnection in HED plasmas. |
Thursday, October 20, 2022 10:18AM - 10:30AM |
TO06.00005: Characterizing the effect of strong magnetization in cylindrically imploded hot dense plasmas using dopant spectroscopy techniques and benchmarked simulations Mathieu Bailly-Grandvaux, Ricardo Florido, Gabriel Peréz-Callejo, Christopher A Walsh, Christopher McGuffey, Joao J Santos, Francisco Suzuki-Vidal, Christos Vlachos, Jacob Saret, Marco A Gigosos, Philip BRADFORD, Roberto C Mancini, Farhat N Beg The increased strength and volume of magnetic fields that can now be applied in experiments is pushing the frontiers of magnetized High-Energy-Density Physics (HEDP), as shown by the recent success of the Magnetized-Liner Inertial Fusion (MagLIF) scheme, as well as the subsequent study of magnetized Inertial Confinement Fusion (ICF) implosions to relax ignition constraints. The physics of magnetized transport in Magneto-Hydro-Dynamic (MHD) models warrants experimental validation. In addition, the interpretation of measurements from complex magnetized experiments requires novel and accurate modeling, such as detailed atomic and radiation transport physics for spectroscopy analysis. |
Thursday, October 20, 2022 10:30AM - 10:42AM |
TO06.00006: Long risetime pulsed power as a driver for magnetized experiments in high energy density physics Simon C Bott-Suzuki, Jacob T Banasek, Samuel W Cordaro, Joshua Simpson, Simon N Bland, Susan Parker, Jiaqi Yan Experiments investigating basic plasma physics, inertial fusion and laboratory astrophysics in the high energy density regime detailed design and analysis. Recent work on the COBRA generator (1MA, 100ns) and the Bertha generator (1.1μs, 200kA) indicate that plasma acceleration in pulsed power experiments depends on the drive parameters, and so it becomes feasible to field experimental studies with specific requirements on the correct generator when options are available. Since the system evolution depends on the energy delivery timescale, long drive time (~1ms) experiments can be an advantage. ‘Steady-state’ conditions can be generated for magnetized flow and shock systems, and compression and implosion loads can take advantage of an energy-rich driver. |
Thursday, October 20, 2022 10:42AM - 10:54AM |
TO06.00007: Development of a Faraday Rotation Diagnostic at 1-MA and Diagnosis of Magnetic Field Distribution in Gas-Puff Z-Pinch Implosions Euan Freeman, David A Hammer, Eric S Lavine, William M Potter Gas-puff Z-pinch implosions are magnetically driven implosions of an annular plasma sheath that starts from a cylindrically symmetric gas puff and is compressed onto axis. The distribution of current in this imploding plasma sheath is currently under study. Progress in development of a Faraday Rotation magnetic field diagnostic and measurements of the magnetic field distribution, and thus the current distribution, in the imploding plasma are presented and discussed. The gas-puff Z-pinches are generated on the 1-MA COBRA generator at Cornell University [J. B. Greenly et al., Rev. Sci. Instrum. 79, 073501 (2008)] using a triaxial gas puff nozzle, in which plasmas produced from outer and inner annular nozzles collapse onto a central gas jet, compressing it. The plasmas are generated with current rise times varying from 100-200ns using carbon dioxide and argon gas. The Faraday Rotation measurements are combined with gated visible-UV light self-emission images, XUV (extreme ultraviolet) quadrant camera images, and interferometry measurements to diagnose the implosion dynamics and the electron density. The data presented show the magnetic-field distribution in the plasma with higher spatial resolution and better contrast than previously fielded on the COBRA generator. |
Thursday, October 20, 2022 10:54AM - 11:06AM |
TO06.00008: Numerical Modeling of Laser-Driven Turbulent Plasmas to Study Fluctuation Dynamo and the Role of Astrophysical Magnetic Fields Yingchao Lu, Adam Reyes, Dustin Froula, Petros Tzeferacos, Archie F Bott, Scott Feister, Benjamin Khiar, Jena Meinecke, Hannah Poole, Laura E Chen, Alexander A Schekochihin, Gianluca Gregori, Chikang Li, Hye-Sook Park, Bruce A Remington, James S Ross, Alexis Casner, Don Q Lamb Dynamo in astrophysical turbulence is a key process for amplifying magnetic fields. The advent of high-power laser systems, along with the scaling of magnetohydrodynamics (MHD), has made it possible to recreate astrophysical conditions and processes in terrestrial laboratories. Our recent work has studied the role of magnetic fields with large magnetic Reynolds numbers, above-unity magnetic Prandtl numbers, and in the supersonic and radiative regimes. We present 3-D radiation-MHD FLASH simulations used to design and interpret laser-driven plasma experiments of fluctuation dynamo. At the National Ignition Facility, we demonstrated that magnetized turbulence can strongly suppress local heat transport by two orders of magnitude or more, relevant to the heat transport in astrophysical plasmas in galaxy clusters. On Laser Mégajoule PETAL, we created a magnetized, turbulent, and supersonic plasma that can be applied to understanding turbulence and field amplification in supersonic regimes such as those in the interstellar medium. We present an overview of the design and interpretation of these experiments using the FLASH code. We validated and compared the numerical results with experimental data using synthetic diagnostics such as proton radiography, Thomson scattering, and x-ray self-emission. |
Thursday, October 20, 2022 11:06AM - 11:18AM |
TO06.00009: Detailed benchmarking of the Nernst effect in magnetized HED plasma Sophia Malko, Chris A Walsh, Derek B Schaeffer, Gennady Fiksel, Aaron M Hansen, Adam J Harvey-Thompson, Daniel E Ruiz, Matthew R Weis, Peter V Heuer, Jonathan R Davies, Cameron A Frank, Arijit Bose, William R Fox The Nernst effect plays a dominant role in the magnetic flux transport in magnetized high energy density plasma with high β and large temperature gradients relevant in laboratory astrophysics and magneto-inertial fusion applications, particularly in MagLIF preheat. The detailed experimental benchmarking of the numerical models that include Nernst effect are crucial and required for understanding how to control the magnetized plasma systems. |
Thursday, October 20, 2022 11:18AM - 11:30AM |
TO06.00010: Pulsed-power magnetized shocks under an external magnetic field Raul F Melean, Rachel Young, Sallee R Klein, Akash P Shah, Trevor J Smith, George V Dowhan, Brendan J Sporer, Paul C Campbell, Nicholas M Jordan, Ryan D McBride, R P Drake, Carolyn C Kuranz We present the results of the magnetized plasma jets and magnetized shock experimental campaign on the Michigan Accelerator for Inductive Z-Pinch Experiments (MAIZE) in the Plasma, Pulsed Power, and Microwave Laboratory at the University of Michigan. This experiment aims to explore the interactions of magnetized plasma jets created by conical wire-arrays and the behavior of shocks generated by collisions with a solid obstacle in the presence of an external magnetic field. To generate the magnetized plasma flows, we used MAIZE to ablate 100-micron, aluminum wire arrays with currents in the order of 500 kA with a rise time of 250 ns. We use a conical array to drive an axial plasma jet, while an externally powered Helmholtz coil provides a uniform axial magnetic field we can vary from 0.5 to 5 T. We examine the characteristics and behavior of the shock layer through the analysis of shadowgraphy and interferometry data and compare the effects of the external magnetic field on the evolution of the magnetized plasma and the shock layer. |
Thursday, October 20, 2022 11:30AM - 11:42AM |
TO06.00011: Enhancing high fluence bremsstrahlung x-ray source via magnetic fields Patrick Poole, Mark J May, Gregory E Kemp, Klaus Widmann, Brent E Blue A high fluence source of hard x-rays (30+ keV) is desired for extreme radiation effects testing but it is challenging to boost yields in this energy range using existing laser-driven K-alpha or pulsed-power bremsstrahlung capabilities. An alternative scheme being developed enhances typically undesired laser-plasma instabilities to generate hot electrons that convert to bremsstrahlung x-ray emission in high-Z target walls. Experiments on Omega and NIF have been performed varying hohlraum plasma conditions to strengthen and enhance plasma waves, most recently using strong external magnetic field (10’s of T) to prolong favorable plasma conditions for x-ray generation and resulting in 6x enhancement over non magnetized outputs. These experimental results will be discussed along with supporting simulations. |
Thursday, October 20, 2022 11:42AM - 11:54AM |
TO06.00012: Formation of High-Density Field Reversed Configurations on a Linear Transformer Driver Brendan J Sporer, Akash P Shah, George V Dowhan, Trevor J Smith, Joe M Chen, Stephen A Slutz, Nicholas M Jordan, Ryan D McBride Simulations by Slutz et al. [1] have shown the potential for impressive fusion yield from compression of high-density, high-applied-field (10-30+ T), centimeter-scale field reversed configurations (FRCs) via solid liners imploded by the Z-machine (20 MA, 100 ns). In practice, such experiments could be done on Z with a similar platform to MagLIF, using bias coils in combination with helical AutoMag-type liners [2] to produce a reversing axial field preceding the implosion. |
Thursday, October 20, 2022 11:54AM - 12:06PM |
TO06.00013: The inadequacy of a magnetohydrodynamic approach to the Biermann battery Christopher P Ridgers Magnetic fields can be generated in plasmas by the Biermann battery when the electric field produced by the electron pressure gradient has a curl. The commonly employed magnetohydrodynamic (MHD) model of the Biermann battery breaks down when the electron distribution function is distorted away from Maxwellian. Using both MHD and kinetic simulations of a laser-plasma interaction relevant to inertial confinement fusion we have shown that this distortion can reduce the Biermann-producing electric field by around 50%. More importantly, the use of a flux limiter in an MHD treatment to deal with the effect of the non-Maxwellian electron distribution on electron thermal transport leads to a completely unphysical prediction of the Biermann-producing electric field and so results in erroneous predictions for the generated magnetic field. |
Thursday, October 20, 2022 12:06PM - 12:18PM |
TO06.00014: Vortex-driven ultrahigh magnetic field generation in microtube implosion Masakatsu Murakami, Yanjun Gu, Javier Honrubia Microtube implosion is a novel scheme to generate ultrahigh magnetic fields of the megatesla order. These implosions are driven by ultraintense and ultrashort laser pulses. In its original concept, seeded magnetic fields are required to deflect ions and electron flows toward the cylindrical center to generate spin currents and thus ultrahigh magnetic fields. We have recently found that an optimally designed micro-fabrication can enable us to generate ultrahigh magnetic fields in a vortex-driven microtube implosion even without the seeded magnetic fields. Using multi-dimensional particle-in-cell simulations, we clarify the underlying physics of the structured microtube target. |
Thursday, October 20, 2022 12:18PM - 12:30PM |
TO06.00015: Stability of perpendicular MHD shocks in materials with ideal and non-ideal EoS Andrés Calvo-Rivera, Fernando Garcia Rubio, Cesar Huete, Alexander L Velikovich Magnetically assisted indirect-drive laser fusion, as well as MagLIF and Staged Z Pinch pulsed-power approaches to the ICF, involve strong shock waves propagating in a magnetized plasma. Shock waves, which play a dominant role in thermalizing the kinetic energy generated in the implosion stage, are typically perturbed by the drive's non-uniformity and wrinkle responding to upstream disturbances. We report a theoretical analysis of the stability of planar perpendicular MHD shocks propagating in a medium with an arbitrary equation of state (EoS) to interchange perturbation modes. Then the effect of a transverse magnetic field is translated into a modification of the EoS, making it possible to reduce our MHD problem to the classical D'yakov-Kontorovich (DK) shock-front stability analysis. In contrast with gasdynamic shocks, which are stable in ideal gases independently of shock strength and specific heat ratio (gamma), strong perpendicular MHD shocks exhibit the DK instability in plasmas with gamma>1+sqrt(2). The shock fronts in van der Waals fluids that are DK-unstable without a magnetic field are stabilized by its presence if the magnetic pressure is high enough. Shock fronts in simple metals at pressures not exceeding several Mbar are stable with or without the magnetic field. |
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