Marginal stability constraint on runaway electron distribution
Abstract
High-frequency kinetic instabilities of the strongly anisotropic runaway electrons (RE) can enhance the pitch-angle scattering of the runaways significantly. This wave-induced scattering can easily prevail over runaway scattering on high-Z impurities. In a steady state, collisional damping balances the kinetic drive of the unstable waves, keeping the RE distribution function at marginal stability. The marginal stability constraint limits the achievable RE densities and the shape of the RE distribution function. In this study, we consider whistler and compressional Alfvén waves as the primary source of enhanced elastic scattering of the runaways. By balancing the anomalous Doppler resonance drive with the collisional wave damping, we find the RE distribution function in the ultra-relativistic range of the phase space. We also derive an expression for the spectral energy density of the waves. We show that the power needed to compensate for the wave dissipation is negligible compared to the work of the electric field. The latter is in balance with the synchrotron losses of the runaway electrons.
- Publication Date:
- Research Org.:
- University of Texas, Austin, TX (United States). Institute for Fusion Studies
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1908357
- Alternate Identifier(s):
- OSTI ID: 1923124
- Grant/Contract Number:
- SC0016283; DEFG02-04ER54742; DESC0016283
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Physics of Plasmas
- Additional Journal Information:
- Journal Volume: 30; Journal Issue: 2; Journal ID: ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Elastic scattering; Synchrotron radiation; Runaway electrons; Whistler waves; Quasilinear theory
Citation Formats
Breizman, B. N., and Kiramov, Dimitri I. Marginal stability constraint on runaway electron distribution. United States: N. p., 2023.
Web. doi:10.1063/5.0130558.
Breizman, B. N., & Kiramov, Dimitri I. Marginal stability constraint on runaway electron distribution. United States. https://doi.org/10.1063/5.0130558
Breizman, B. N., and Kiramov, Dimitri I. Thu .
"Marginal stability constraint on runaway electron distribution". United States. https://doi.org/10.1063/5.0130558. https://www.osti.gov/servlets/purl/1908357.
@article{osti_1908357,
title = {Marginal stability constraint on runaway electron distribution},
author = {Breizman, B. N. and Kiramov, Dimitri I.},
abstractNote = {High-frequency kinetic instabilities of the strongly anisotropic runaway electrons (RE) can enhance the pitch-angle scattering of the runaways significantly. This wave-induced scattering can easily prevail over runaway scattering on high-Z impurities. In a steady state, collisional damping balances the kinetic drive of the unstable waves, keeping the RE distribution function at marginal stability. The marginal stability constraint limits the achievable RE densities and the shape of the RE distribution function. In this study, we consider whistler and compressional Alfvén waves as the primary source of enhanced elastic scattering of the runaways. By balancing the anomalous Doppler resonance drive with the collisional wave damping, we find the RE distribution function in the ultra-relativistic range of the phase space. We also derive an expression for the spectral energy density of the waves. We show that the power needed to compensate for the wave dissipation is negligible compared to the work of the electric field. The latter is in balance with the synchrotron losses of the runaway electrons.},
doi = {10.1063/5.0130558},
journal = {Physics of Plasmas},
number = 2,
volume = 30,
place = {United States},
year = {Thu Feb 02 00:00:00 EST 2023},
month = {Thu Feb 02 00:00:00 EST 2023}
}
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