Observation of rapid frequency chirping instabilities driven by runaway electrons in a tokamak

被引:30
|
作者
Lvovskiy, A. [1 ]
Heidbrink, W. W. [2 ]
Paz-Soldan, C. [3 ]
Spong, D. A. [4 ]
Dal Molin, A. [5 ]
Eidietis, N. W. [3 ]
Nocente, M. [5 ]
Shiraki, D. [4 ]
Thome, K. E. [3 ]
机构
[1] Oak Ridge Associated Univ, Oak Ridge, TN 37830 USA
[2] Univ Calif Irvine, Irvine, CA USA
[3] Gen Atom, San Diego, CA USA
[4] Oak Ridge Natl Lab, Oak Ridge, TN USA
[5] Univ Milano Bicocca, Dipartimento Fis, Milan, Italy
关键词
runaway electrons; frequency chirping; kinetic instabilities; CHORUS; MODES;
D O I
10.1088/1741-4326/ab4405
中图分类号
O35 [流体力学]; O53 [等离子体物理学];
学科分类号
070204 ; 080103 ; 080704 ;
摘要
We report the first observation of chirping instabilities driven by runaway electrons (REs) in a tokamak. The instabilities are accessed during the post-disruption RE beam stage in a low density background plasma (n(e) < 10(19) m(-3)) on DIII-D. The chirping instabilities are observed when a decelerating loop voltage is applied to the RE beam. The frequency chirping is detected in two distinct frequency bands: 0.1-10 MHz and 30-80 MHz. The mode frequency increases linearly when the toroidal magnetic field sensed by the RE beam increases. The frequency chirps by 0.3-2.4 MHz on a timescale of 1 ms. Modification of the RE distribution function is directly measured during the chirping in the low-frequency band consistent with the hole-clump model for frequency chirping. The low-frequency instabilities also correlate with an increase of intermittent RE loss from the plasma. These observations provide a novel experimental platform for fundamental studies of nonlinear chirping. They also support continued investigation of opportunities to utilize kinetic instabilities for RE mitigation in a tokamak reactor.
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页数:6
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