Simulation of MGI efficiency for plasma energy conversion into Ar radiation in JET and implications for ITER

Abstract

Effectiveness of massive gas injection (MGI) for mitigation of disruptive wall damage has been investigated. Cross-reference analysis of the available JET experiments on MGI and their simulations with the TOKES code allow suggesting that in JET conditions one can convert into radiation the electron thermal energy and the plasma current energy, but the ion thermal energy does not convert into radiation because of very ineffective excitation of injected noble gas (NG) ions by D ions and long equipartition time between D ions and electrons. The model assumes rather high electron temperature during current quench (CQ), which contradicts with its time duration. Rough extrapolation of the result on ITER conditions shows that one can expect irradiation of total plasma energy if CQ duration in ITER is not shorter as in JET.