Speaker
Chang Liu
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.4005.pdf
Whistler wave instabilities of runaway electrons in tokamaks
Chang Liu1 , Eero Hirvijoki1 , Dylan Brennan2 , Guo-yong Fu1,3 , Amitava Bhattacharjee1,2
1 Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
2 Princeton University, Princeton, New Jersey 08544, USA
3 Zhejiang University, Hangzhou, Zhejiang, 310027, China
Highly energetic runaway electron beam can be generated in tokamak disruptions, which can
be destructive to the device. The runaway electron beam has a bump-on-tail and anisotropic
distribution due to parallel acceleration and radiation reaction, thus can be susceptible to kinetic
instabilities. In this work the whistler wave instabilities associated with runaway electron beam
is investigated using a newly-developed simulation model, and the anomalous dissipation and
the fast pitch angle scattering of runaway electrons in low energy are explained[1].
The interaction of runaway electron avalanche (a)
10.0
7.5
and the kinetic instabilities are studied self-
(mc)
5.0
consistently using quasilinear model. Results show
p
2.5
0.0
that excited whistler waves can cause electrons to 0 5 10 15 20
(b)
25
10.0
be scattered to large pitch angle (Fig. 1) and form 7.5
(mc)
5.0
vortices in momentum space, creating a new en-
p
2.5
0.0
ergy loss channel, and enhance the radiations. This 0 5 10 15 20 25
p (mc)
explains the higher-than-expected critical electric
Figure 1: Compared to the case without kinetic in-
field and the loss of runaway electron population
stabilities (a), the electrons scattered by whistler
in low energy regime identified experimentally[2]. waves has broader distribution in pitch angle (b).
The whistler waves excited in runaway electron ex-
periments have recently been measured in both flattop phases[3] and post-disruption stages,
which is consistent with the simulation results. The fast growth of electron cyclotron emission
(ECE) signals observed in experiments is reproduced by a synthetic diagnostic tool. In addition,
the oscillations of the ECE signals is explained through the nonlinear interactions between the
excitation of whistler waves and the scattering of electron distribution function.
References
[1] C. Liu, E. Hirvijoki, G. Y. Fu, D. P. Brennan, A. Bhattacharjee, and C. Paz-Soldan, arXiv:1801.01827 (2018).
[2] C. Paz-Soldan, C. M. Cooper, P. Aleynikov, D. C. Pace, N. W. Eidietis, D. P. Brennan, R. S. Granetz, E. M.
Hollmann, C. Liu, A. Lvovskiy, R. A. Moyer, and D. Shiraki, Phys. Rev. Lett. 118, 255002 (2017).
[3] D. A. Spong, W. W. Heidbrink, C. Paz-Soldan, X. D. Du, K. E. Thome, M. A. V. Zeeland, C. Collins, A.
Lvovskiy, R. A. Moyer, D. P. Brennan, C. Liu, E. F. Jaeger, and C. Lau, submitted to Phys. Rev. Lett.
