Assessment of Feasibility of Helium Ash Exhaust and Heat Removal by Pumped-Limiter in Tokamak Fusion Reactor

Abstract

A detailed calculation of the behavior of fuel and He particles in tokamak reactor with pumped-limiter is performed by one-dimensional tokamak transport code. Energy of neutral particles flowing back from limiter chamber is calculated by two-dimensional Monte Carlo neutral code. Feasibility of He ash exhaust and heat removal by the pumped-limiter are analyzed. Following features of the pumped-limiter are clarified: 1. Electron temperature decays rapidly in radial direction in scrape-off layer, while density profile is broader than that of temperature. 2. Helium accumulation in main plasma can be kept at desired level by rather short limiter and moderate pumping system. 3. Minimum amount of tritium pumped out little depends on limiter length. 4. Although high temperature plasma in scrape-off layer could be realized by large pumping and ideal pellet injection, it is not sufficiently high to reduce the erosion of the limiter surface and the leading edge. In conclusion, He ash exhaust may be possible by the p...