Tracking Hot Electron Evolution and Anisotropy-Driven Whistler Emissions on LAPD
POSTER
Abstract
A novel diagnostic is used to investigate the spatiotemporal evolution of hot electron populations in a magnetic mirror configuration on the Large Plasma Device (LAPD) at UCLA. LAPD is a 20 m long, 60 cm diameter linear plasma device. In the mirror setup, energetic electrons up to 1 MeV are produced with X-mode microwave heating (2.45 GHz, up to 10 kW) near the midplane. Tungsten pellet injection enables non-perturbative detection of these electrons via X-ray emissions, which reassembles both spatial structure and temporal evolution of the hot electrons.
Electrons driven by perpendicular microwave heating generates whistler waves via temperature-anisotropy instabilities. The resulting waves exhibit periodic bursts resembling whistler-mode chorus emissions observed in near-Earth space. Particle-in-cell simulations confirm that repeated cycles of anisotropy buildup and whistler-induced pitch-angle scattering govern the observed temporal structure in lab. A gradual frequency downshift is also seen, consistent with rising parallel electron temperature and linear instability predictions.
Together, these studies demonstrate a new capability for diagnosing and controlling energetic electron behavior in magnetized plasmas. The combined diagnostic and wave-excitation results offer insight into fundamental wave–particle interactions relevant to space radiation belts, plasma heating, and runaway electron dynamics in fusion systems.
Electrons driven by perpendicular microwave heating generates whistler waves via temperature-anisotropy instabilities. The resulting waves exhibit periodic bursts resembling whistler-mode chorus emissions observed in near-Earth space. Particle-in-cell simulations confirm that repeated cycles of anisotropy buildup and whistler-induced pitch-angle scattering govern the observed temporal structure in lab. A gradual frequency downshift is also seen, consistent with rising parallel electron temperature and linear instability predictions.
Together, these studies demonstrate a new capability for diagnosing and controlling energetic electron behavior in magnetized plasmas. The combined diagnostic and wave-excitation results offer insight into fundamental wave–particle interactions relevant to space radiation belts, plasma heating, and runaway electron dynamics in fusion systems.
Publication: https://arxiv.org/abs/2504.06383
Presenters
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Jia Han
University of California, Los Angeles, University of California Los Angeles
Authors
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Jia Han
University of California, Los Angeles, University of California Los Angeles
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Patrick Pribyl
University of California , Los Angeles, University of California, Los Angeles
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Walter N Gekelman
University of California, Los Angeles
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Donglai Ma
University of California, Los Angeles
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Xin An
University of California, Los Angeles
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Jacob Bortnik
University of California, Los Angeles