Collisionless Larmor Coupling of a laser plasma with a magnetized ambient plasma
POSTER
Abstract
We experimentally investigate the collisionless coupling leading to the cross-field acceleration and subsequent rotation of the ambient plasma during the perpendicular expansion of a laser-produced plasma in a magnetized background plasma.
In our experiment performed on the Large Plasma Device (LAPD), a super-alfvenic, laser-produced carbon plasma expands in a magnetized ambient helium plasma and forms a diamagnetic cavity. The streaming of the super-Alfvenic debris ions leads to the transverse energization of background helium ions via collisionless Larmor coupling. The magnetic fields are mapped out in 2D using a magnetic flux probe. The energized background plasma is observed and tracked using filtered self-emission of excited He+ ions at 468.6 nm, observed with filtered fast-gate imaging. Spatially and temporally resolved Doppler-shift spectroscopy shows that He+ ions are accelerated radially outward and then rotate in a motion consistent with Larmor coupling. Additionally, electric potential measurements with an emissive probe indicate that the transverse dynamics of the background ions cannot be explained by the electrostatic field.
In our experiment performed on the Large Plasma Device (LAPD), a super-alfvenic, laser-produced carbon plasma expands in a magnetized ambient helium plasma and forms a diamagnetic cavity. The streaming of the super-Alfvenic debris ions leads to the transverse energization of background helium ions via collisionless Larmor coupling. The magnetic fields are mapped out in 2D using a magnetic flux probe. The energized background plasma is observed and tracked using filtered self-emission of excited He+ ions at 468.6 nm, observed with filtered fast-gate imaging. Spatially and temporally resolved Doppler-shift spectroscopy shows that He+ ions are accelerated radially outward and then rotate in a motion consistent with Larmor coupling. Additionally, electric potential measurements with an emissive probe indicate that the transverse dynamics of the background ions cannot be explained by the electrostatic field.
Presenters
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Lucas Rovige
University of California, Los Angeles
Authors
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Lucas Rovige
University of California, Los Angeles
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Robert S Dorst
University of California, Los Angeles
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Ari Le
Los Alamos National Laboratory
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Jessica Jean Pilgram
University of California, Los Angeles
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Carmen G Constantin
University of California, Los Angeles
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David Jeffrey Larson
Lawrence Livermore Natl Lab
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Steve T Vincena
UCLA, University of California, Los Angeles
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Shreekrishna Tripathi
University of California, Los Angeles, Department of Physics and Astronomy, University of California, Los Angeles, UCLA
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Misa Cowee
Los Alamos National Laboratory
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Derek B Schaeffer
University of California, Los Angeles, UCLA
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Christoph Niemann
University of California, Los Angeles