Bulletin of the American Physical Society
62nd Annual Meeting of the APS Division of Plasma Physics
Volume 65, Number 11
Monday–Friday, November 9–13, 2020; Remote; Time Zone: Central Standard Time, USA
Session CP14: Poster Session: Fundamental Plasmas: Plasma Shocks (2:00pm - 5:00pm)On Demand
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CP14.00001: Establishing the x-ray diagnostic capabilities on the Magnetized Shock Experiment J. Boguski, T. E. Weber, I. A. Bean, G. A. Wurden Soft x-ray (0.1 -- 10 keV) diagnostics are a workhorse for providing information on the temperatures and dynamics of plasmas. Additionally, hard x-rays (10 -- 100 keV) can provide key insight into the kinetics of high-energy electron populations, such as those generated in collisionless shocks, high energy density physics applications, and outputs of intense laboratory x-ray sources. The Magnetized Shock Experiment (MSX) at LANL is a platform to study the physics of kinetic shocks and radiation generation processes using stagnating flow-dominated magnetized plasmoids. To develop an understanding of the expected x-ray outputs, we have built a multichannel x-ray detector using a series of pinhole aperture, transmission-foil-based ``Ross'' bandpass filters coupled to phosphor-coated windows to convert the x-rays to visible photons and PMTs for sensitive, time-resolved detection. A vacuum region separates the foils from the phosphor screen and PMT detector so as to make the output signal immune to incident plasma electrons. This system provides broadband coverage ranging from \textasciitilde 0.1 keV to \textasciitilde 100 keV with rough binning of photon output, and will serve as a basis for further refinement and development of more sophisticated x-ray diagnostics. Access to onsite soft and hard x-ray calibration tests stands enables accelerated development of detectors and rapid testing of new materials and designs. [Preview Abstract] |
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CP14.00002: Shock Turbulence Interaction with Plasma Viscosity Michael Zhang, Seth Davidovits, Chris Weber, Nathaniel Fisch Plasma viscosity is a strong function of the background temperature. In strong shocks, the temperature of the plasma can increase immensely. We investigate how turbulence in a plasma may be dissipated under consideration of these combined effects, as was previously found for the case of a turbulent plasma undergoing metric compression \footnote{S. Davidovits \& N. J. Fisch, \textbf{Phy. Rev. Lett.} 116, 2016}. When the net increase of viscosity is not strong, nonunique outcomes of final turbulent energy under multiple shocks are also considered. [Preview Abstract] |
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CP14.00003: Characterization of Multi-Ion-Species Shock Structures in Railgun-Driven Plasma Jet Experiments Ameer I. Mohammed, Maximilian K. Schneider, Colin S. Adams Shocks are induced and characterized by colliding high-Mach-number plasma jets with stagnated plasma. A linear railgun serves as the plasma source, where injected argon gas mixes with impurities ablated from the internal components of the gun to form multi-ion-species plasma jets. These jets exist in a collisional regime, with density $\approx10^{16}~\mathrm{cm^{-3}}$ and temperature $\approx2~\mathrm{eV}$. The collision event produces a stagnation layer which is characterized using multi-chord interferometry, fast photography, and spatially-resolved spectroscopy. Plasma parameters measured and inferred from these diagnostics suggest that this stagnation layer is consistent with the formation of a collisional shock. Present efforts focus on spatially resolving the distribution of ion species in the pre- and post-shock plasma. The resulting data will have the potential to validate physics models relevant to astrophysical and high-energy-density plasmas. [Preview Abstract] |
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CP14.00004: Particle acceleration in relativistic collisionless shocks: emergence of Fermi acceleration and energy bifurcation Roopendra Singh Rajawat, Vladimir Khudik, Gennady Shvets A numerical study of Weibel-mediated collisionless shocks has been carried out by means of multidimensional first-principle particle-in-cell simulation code. In the simulations, the collisionless shock is generated via collision of two relativistic electron-positron plasma shells having initial kinetic energies $\gamma_{0}mc^{2}$. In the downstream region of the shock, we have identified two group of particles: having moderate $\gamma \sim \gamma_{0}$ and large kinetic energies $\gamma >> \gamma_{0}$. To get insight of the acceleration/deceleration mechanism, kinetic energy (KE) of the particles in these groups has been decomposed into the works done by the transverse and longitudinal electric fields. It is found that in the first group the KE takes equal contribution from both components of the electric field, while in the second group the KE takes most of the energy from the transverse electric field: the ratio of work done by the transverse and longitudinal electric field is found out to be dependent on the time. The position of the separation point between these two groups remains constant with time and is found to be $\gamma/\gamma_{0} \sim 2$. The study has been extended for the perpendicular magnetized relativistic collisionless shocks. [Preview Abstract] |
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