Droplet transport from main HT-6M poloidal limiter

Abstract

The HT-6M is a tokamak installed only with a main metallic poloidal limiter, which may not tolerate energy deposition due to a limited plasma-wetted area. This leads to the production of fresh metallic impurities, including macro-particles, in its main vessel. The macro-particles are transported and then ablated far away from where they were created. Understanding transport and ablation is beneficial to characterize impurity generation in the HT-6M, which will be recommissioned in Thailand in the next few years. A computational study simulated the motion of macro-particles in the HT-6M using the specifically written Dust and Droplet Tracking (DDT) code with the steady state HT-6M plasma profiles produced from the Transport Analyzing System for tokamaK (TASK) code. The results showed that a substantial amount of vapor containing impurities in the scrape-off layer (SOL) plasma was produced by the ablation of the liquid macro-particles emitted from the HT-6M poloidal limiter when the macro-particles were located near the limiter and nearby plasma-facing components (PFCs). Heavy ablation on the macro-particles transported directly towards the core plasma led to complete vaporization locally. The updated DDT code is discussed.