Formation and termination of runaway beams in ITER disruptions

Nuclear Fushion

article

J.R. Martín-Solís¹  A. Loarte²  M. Lehnen² 

[1] Universidad Carlos III de Madrid, Avenida de la Universidad 30;ITER Organization

关键词: disruption;    runaway electrons;    runaway seed;    runaway avalanche;    ITER;   

DOI  :  10.1088/1741-4326/aa6939

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

A self-consistent analysis of the relevant physics regarding the formation and termination of runaway beams during mitigated disruptions by Ar and Ne injection is presented for selected ITER scenarios with the aim of improving our understanding of the physics underlying the runaway heat loads onto the plasma facing components (PFCs) and identifying open issues for developing and accessing disruption mitigation schemes for ITER. This is carried out by means of simplified models, but still retaining sufficient details of the key physical processes, including: (a) the expected dominant runaway generation mechanisms (avalanche and primary runaway seeds: Dreicer and hot tail runaway generation, tritium decay and Compton scattering ofγrays emitted by the activated wall), (b) effects associated with the plasma and runaway current density profile shape, and (c) corrections to the runaway dynamics to account for the collisions of the runaways with the partially stripped impurity ions, which are found to have strong effects leading to low runaway current generation and low energy conversion during current termination for mitigated disruptions by noble gas injection (particularly for Ne injection) for the shortest current quench times compatible with acceptable forces on the ITER vessel and in-vessel components ({{au}_{ext{res}}}sim 22~ext{ms} ). For the case of long current quench times ({{au}_{ext{res}}}sim 66~ext{ms} ), runaway beams up to  ∼10 MA can be generated during the disruption current quench and, if the termination of the runaway current is slow enough, the generation of runaways by the avalanche mechanism can play an important role, increasing substantially the energy deposited by the runaways onto the PFCs up to a few hundreds of MJs. Mixed impurity (Ar or Ne) plus deuterium injection proves to be effective in controlling the formation of the runaway current during the current quench, even for the longest current quench times, as well as in decreasing the energy deposited on the runaway electrons during current termination.

【 授权许可】

Unknown