Summary of recent studies of beam-driven BAE and chirping modes in DIII-D
Summary of recent studies of beam-driven BAE and chirping modes in DIII-D
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DOI：
10.1088/0029-5515/35/12/i08
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发表时间：
1995-05
期刊：
影响因子：
3.3
通讯作者：
W. Heidbrink;E. Carolipio;R. James;E. Strait
中科院分区：
文献类型：
--
作者：
W. Heidbrink;E. Carolipio;R. James;E. Strait
In high beta DIII-D plasmas with intense neutral-beam injection, beta-induced Alfven eigenmodes (BAE modes) are observed. These instabilities can cause concentrated losses of >50% of the fast ions and thus are of concern for future devices. We have now observed BAE modes and resultant fast-ion loss in full-field (2.0 T) discharges where the ratio of parallel velocity to the Alfven speed is {upsilon}{sub parallel}/{upsilon}{sub A} {approx_equal}0.3. In a few discharges, we have also observed a new instability, a ``chirping`` mode. These modes have frequencies between 50 and 200 kHz that ``whistle`` down a factor of two in a single 2 ms burst. They occur in plasmas with relatively large values of fast-ion beta ({l_angle}{beta}{sub {integral}}{r_angle} {approx_gt}1%), Alfven speed ({upsilon}{sub {parallel}}/{upsilon}{sub A}{approx_gt}0.5), and plasma rotation ({integral}rot >20 kHz). In contrast to the usual Alfven modes, which are fluid modes of the background plasma, the chirping instabilities seem to be beam modes that are nearly stationary in the plasma frame.
In high beta DIII-D plasmas with intense neutral-beam injection, beta-induced Alfven eigenmodes (BAE modes) are observed. These instabilities can cause concentrated losses of >50% of the fast ions and thus are of concern for future devices. We have now observed BAE modes and resultant fast-ion loss in full-field (2.0 T) discharges where the ratio of parallel velocity to the Alfven speed is {upsilon}{sub parallel}/{upsilon}{sub A} {approx_equal}0.3. In a few discharges, we have also observed a new instability, a ``chirping`` mode. These modes have frequencies between 50 and 200 kHz that ``whistle`` down a factor of two in a single 2 ms burst. They occur in plasmas with relatively large values of fast-ion beta ({l_angle}{beta}{sub {integral}}{r_angle} {approx_gt}1%), Alfven speed ({upsilon}{sub {parallel}}/{upsilon}{sub A}{approx_gt}0.5), and plasma rotation ({integral}rot >20 kHz). In contrast to the usual Alfven modes, which are fluid modes of the background plasma, the chirping instabilities seem to be beam modes that are nearly stationary in the plasma frame.