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approvedsherwood_2017.pdf2017-05-12 13:44:33Chang Liu

Abstracts

Author: Chang Liu
Requested Type: Poster
Submitted: 2017-03-17 10:26:37

Co-authors: Dylan P. Brenna, Allen H. Boozer, Amitava Bhattacharjee

Contact Info:
Princeton Plasma Physics Laboratory
100 Stellarator Rd
Princeton, New Jersey   08540
USA

Abstract Text:
The mitigation of runaway electrons generated during tokamak disruptions is an important and urgent topic for large tokamak experiments. Understanding the physics which can enhance scattering and energy loss from the runaways is therefore of great interest. Due to the strongly anisotropic distribution on pitch angle, a runaway electron beam is susceptible to various kinds of kinetic instabilities such as whistler waves. The excited whistler waves can cause significant pitch angle scattering of the beam through wave particle interaction. In this study, we present a hybrid simulation tool for both the runaway electron distribution in momentum space and the whistler wave amplitudes. The wave-particle interaction is studied using the quasilinear approach. Using this tool to study a typical DIII-D discharge with runaway electron generation in the flat-top phase, we find that the whistler wave instabilities can be triggered as the runaway electron density passes a certain threshold. The excited waves can scatter the runaway electrons’ pitch angle in both the low and high energy regimes, and hinder runaway electrons gaining energy. In addition, we have benchmarked the simulation results with the ECE (Electron Cyclotron Emission) signal from the experiment using a newly-developed ECE synthetic diagnostic tool, and find good agreement between the two results. These results demonstrate the possibility of using the whistler wave to alter the runaway electron distribution in momentum space, and provide new paths for runaway electron mitigation in tokamak disruptions.

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