Modeling and simulation of lithium transport and radiation in diverted Pi3 plasmas

Abstract

In this work, we study the transport of lithium impurities as they are transported from the wall where they are sputtered into the core plasma of the experimental device Pi3 that uses solid lithium walls at General Fusion. We perform time-dependent full-orbit simulations of initially neutral lithium impurities entering a Pi3 deuterium plasma that evolve their charge states and follow their full-orbit dynamics in axisymmetric Pi3 plasmas. This is done by extending the capabilities of the KORC-T code [L. Carbajal et al., Phys. Plasmas 24, 042512 (2017); J. Martinell et al., Bulletin of the American Physical Society (American Physical Society, 2020), Vol. 65] to include atomic collisions of ionization, recombination, and charge-exchange (CX) with neutral hydrogenic species by interpolating rates of these atomic processes from OPEN-ADAS tables to local plasma conditions. We assess the effect of hydrogenic neutrals, initial energy of sputtered lithium impurities, and the inclusion of E × B drifts caused by a radial electric field obtained from a radial force balance equation. It is found that both penetration of lithium impurities into the core and electron energy losses are enhanced by the radial electric field, with a weaker dependence on initial energy with which neutral lithium is sputtered off the lithium wall. Hydrogenic neutrals are not found to have a visible effect on transport of lithium impurities. Also, it is shown that ionized lithium impurities are not thermalized with the background deuterium ions at the edge plasma of Pi3 in studied timescale. From an analysis of electron cooling and radiation losses driven by lithium impurities, we find that energy losses are not significant in these plasmas.