Supersonic gas injection on Tore Supra

A fueling system by supersonic pulsed gas injection has been installed on the high field side of Tore Supra. First results are encouraging, demonstrating a fueling efficiency four times higher than that of conventional gas puff. One-dimensional modeling shows that the increase of efficiency is linked to the short injection time and to the prompt cooling of the plasma edge consecutive to the massive injection of matter. Improvements of the system could lead to the formation of a high-β blob which could experience a drift down the magnetic field, analogously to pellet injection, thus further increasing the fueling efficiency of the method.