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 TP11: Poster Session VII: In-Person, Hall A (9:30-11:00am) and Virtual Poster Presentations (11:15am-12:30pm)
MFE: FRC, RFPs etc
ICF: Fast Ignition; Diagnostics; Computational; Laser Plasma Interactions
FUND: Computation
9:30 AM - 12:30 PM
Thursday, October 20, 2022
Room: Exhibit Hall A and Online
Abstract: TP11.00106 : Measurements of the effects of an external B-field on backscattered Stimulated Raman Scattering(SRS) reflectivity*
Presenter:
Alemayehu Bogale
(University of California, San Diego)
Authors:
Alemayehu Bogale
(University of California, San Diego)
Mathieu Bailly-Grandvaux
(UCSD)
Simon Bolanos
(UCSD)
Mario Manuel
(General Atomics - San Diego)
Benjamin J Winjum
(University of California, Los Angeles)
Chris A Walsh
(Lawrence Livermore National Laboratory)
Jacob Saret
(UCSD)
Roman Lee
(University of California, Los Angeles)
Frank S Tsung
(University of California, Los Angeles)
Warren B Mori
(University of California, Los Angeles)
Dustin Froula
(University of Rochester)
Timothy Filkins
(LLE)
Farhat N Beg
(University of California, San Diego)
Collaboration:
Center for Energy Research, UCSD
Office for Advanced Research Computing, UCLA
LLNL
LLE
Laser-plasma instabilities such as Stimulated Raman Scattering (SRS) play a detrimental role in inertial confinement fusion. SRS leads to a loss of energy due to light scattering and preheating of the fuel by suprathermal electrons generated through the decay of electron plasma waves. Recent numerical work has shown that a moderate external magnetic field can mitigate SRS through its influence on wave-particle interactions. A novel platform at the OMEGA-EP laser was developed to study the effect of a 25 T perpendicular magnetic field (using MIFEDS coils) on the backscattered SRS (BSRS) light spectrum from an Argon gas jet target. The Sub-Aperture Backward Scatter diagnostic was fielded to measure the BSRS spectra with a time resolution that enables probing of different plasma conditions on the same shot, via the use of a train of short pulses for the excitation beam. The results attest to a kinetic effect that the B-field has on BSRS reflectivity: (i) when ne<11%ncr, the BSRS reflectivity is enhanced, and (ii) when ne >11%ncr, the B-field reduces the BSRS reflectivity. The X-ray spectrometry confirms that the BSRS occurs in the expected kinetic regime ( kλD ~ 0.2-0.3).
*The experiment was conducted at the Omega Laser Facility at the University of Rochester’s Laboratory for Laser Energetics with the beam time through the National Laser Users’ Facility (NLUF) program. This material is based upon work supported by the Department of Energy, National Nuclear Security Administration under Award Numbers DE-NA0003842 and DE-NA0003856, the University of Rochester, and the New York State Energy Research and Development Authority.
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