Feasibility Study of Magnetic Energy Transfer System in Air-Core Tokamaks

Abstract

During plasma disruption in tokamaks, a large amount of energy will be dissipated in the vacuum vessel (VV) and cause damage to the plasma-facing components. Reducing the energy dissipated in the VV is a direct and valid method to mitigate the damage. This idea has been previously studied on J-TEXT based on a newly developed magnetic energy transfer (MET) system, and its validity has been proved. However, unlike the large air-core tokamaks, J-TEXT is a middle-size tokamak with an iron core and a toroidally isolated VV, which results in a high electromagnetic coupling between the plasma and the energy transfer coils (ETCs). So, it is necessary to study the feasibility of the MET method in air-core tokamaks. Taking EAST as an example, a finite element model is established in this article to analyze the electromagnetic coupling between the plasma, VV, poloidal field (PF) coils, and ETCs. The induced current in the VV and ETCs during plasma disruption is calculated. These analysis results are verified by comparison with the ones from the partial element equivalent circuit (PEEC) method. Then, the evolution of magnetic energy during plasma disruption is analyzed, which shows that 76.9% of magnetic energy will be consumed in the VV. At last, the possible maximum energy transfer efficiency of the energy transfer system is analyzed by changing the number, position, and load parameters of ETCs. The energy transfer efficiency will be within 10% and the reduction of induced current in the VV will be within 20%. To some degree, the analysis in this article proves the feasibility of the MET system in air-core tokamaks, but there will be some engineering difficulties to overcome.