A supersonic gas injection system for fueling and probing fusion plasmas

Abstract

The large gas reservoir surrounding the H-1NF plasma leads to difficulties in achieving the density control required to maximize the plasma temperature. We have designed and tested an alternative fuelling system which uses a double conical nozzle to generate a directed flow of particles into the plasma without adding to the gas inventory in the rest of the vacuum vessel. By using a closed plenum at a programmable pressure and a piezo-electric valve, the particle flux can be dynamically changed in a controlled and quantitative manner. Measurements of the gas jet using constant temperature hot wire anemometry show that, for plenum pressures between 500 and 1000 Torr, the particle injection rate (helium) ranges between 2 × 1020 and 4 × 1020 s-1 with half-cone angles between 5° and 20°. The system has been installed on the H-1NF device and first plasma results indicate localized gas injection consistent with test tank anemometry measurements. Show more