Spatiotemporal Evolution of Runaway Electron Momentum Distributions in Tokamaks
Name
PhysRevLett.118.255002.pdf
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944.02 KB
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Checksum (MD5)
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Author(s)
Paz-Soldan, C.
Cooper, C. M.
Aleynikov, P.
Pace, D. C.
Eidietis, N. W.
Brennan, D. P.
Hollmann, E. M.
Liu, C.
Lvovskiy, A.
Moyer, R. A.
Date Issued
June 2017
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Paz-Soldan, C.; Cooper, C.M.; Aleynikov, P.; Pace, D.C.; Eidietis, N.W. et al. "Spatiotemporal Evolution of Runaway Electron Momentum Distributions in Tokamaks." Physical Review Letters 118, 255002 (June 2017): 1- 6 © 2017 American Physical Society
Version
Final published version
Abstract
Novel spatial, temporal, and energetically resolved measurements of bremsstrahlung hard-x-ray (HXR) emission from runaway electron (RE) populations in tokamaks reveal nonmonotonic RE distribution functions whose properties depend on the interplay of electric field acceleration with collisional and synchrotron damping. Measurements are consistent with theoretical predictions of momentum-space attractors that accumulate runaway electrons. RE distribution functions are measured to shift to a higher energy when the synchrotron force is reduced by decreasing the toroidal magnetic field strength. Increasing the collisional damping by increasing the electron density (at a fixed magnetic and electric field) reduces the energy of the nonmonotonic feature and reduces the HXR growth rate at all energies. Higher-energy HXR growth rates extrapolate to zero at the expected threshold electric field for RE sustainment, while low-energy REs are anomalously lost. The compilation of HXR emission from different sight lines into the plasma yields energy and pitch-angle-resolved RE distributions and demonstrates increasing pitch-angle and radial gradients with energy.
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
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DOI of Published Version
https://doi.org/10.1103/PhysRevLett.118.255002
