Experimental evidence of runaway electron tail generation via localized helical structure in pellet-triggered tokamak disruptions

Nuclear Fushion

article

X.D. Du¹  N.W. Eidietis¹  E.M. Hollmann²  D. Finkenthal³  L. Stagner¹  C. Paz-Soldan¹  E.J. Strait¹  J.L. Barr¹  A. Lvovskiy¹ 

[1] General Atomics;University of California San Diego;Palomar. College

关键词: runaway electrons;    tokamak disruptions;    MHD instabilities;   

DOI  :  10.1088/1741-4326/ac1e5e

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

A novel detector, using stacked BGO crystals, is developed for runaway electron (REs) studies in the DIII-D tokamak. It is able to resolve fast dynamics of high-energy tail formation of REs with an ultra-high time resolution of ∼1  μ s. As a cost, the detector estimates the 'effective' energy of a given shape of γ-ray spectra and sacrifices the energy resolution. In aid of the new measurement capability, a rapid, inhomogeneous growth of RE tail is observed in detail during a major disruption triggered by an argon pellet. It is found that both the population and energy of a well-confined RE tail significantly oscillate at the early period of the growth. The oscillation phase is locked to a slow rotating magnetohydrodynamic instability, which is briefly destabilized for only ∼1 ms at the early period of the current quench. The oscillation ceases promptly, when the mode disappears. The data suggests that the high-energy RE tail is well-confined and accelerated via a localized helical structure in the plasma core.

【 授权许可】

Unknown