Abstract Details
Abstracts
Author: Haotian Mao
Requested Type: Poster
Submitted: 2024-04-12 14:31:33
Co-authors: Y.Zhang, X.Tang
Contact Info:
Los Alamos National Laboratory
3790 Gold Street Apt 5
Los Alamos, 87544
United States of Ame
Abstract Text:
Pellet injection is a standard technique for fueling and disruption mitigation in fusion reactors like ITER. Although the nominal goals of these two applications are similar, namely to deliver materials into the fusion core, there are important distinctions on the specifics. Particularly, for disruption mitigation of tokamak thermal quench, the primary aim is to (1) replace plasma power exhaust at the first wall with line radiation by high-Z impurities, which requires substantial amount of high-Z impurities to be assimilated into the plasma at time scale much shorter than 1 millisecond; and to (2) spread the radiation as uniformly as possible on the first wall, which requires rapid spatial transport and homogenization of high-Z radiators over a flux surface despite the initially local assimilation of the pellets. Therefore, the emphasis on post-assimilation spatial transport and mixing is a critical aspect for successful thermal quench mitigation in a tokamak reactor. Here we employ the first-principles kinetic simulations and analysis to investigate the physics underlying the high-Z impurities assimilation along the magnetic field line from an ablated pellet. We find that, the high-Z impurities’ transport is limited by the cooling front, which is naturally formed when a fusion-grade plasma is intercepted with a cooling spot (a pellet in our case) that represents a deep cooling of the plasma [Zhang et al EPL 141 54002 2023]. Due to the strong collisionality of the high-Z impurities, the impurities’ expansion with different charge state can be described by an averaged charge state. The high-Z impurities assimilation is characterized by an impurity recession front and an impurity expansion front, the speed of the former scales with the cold pellet temperature, while that of the latter is mainly determined by the hot ambient electron temperature.
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