New Valve for Massive Gas Injection in DIII-D

Previous experiments on DIII-D have demonstrated the efficacy of using massive gas injection for disruption mitigation. The new valve has an orifice diameter of 22.3~mm vs 5~mm for the previous valve used from 1998 through 2005. Flows in argon greater than 2$\times$10$^6\,$Torr-l/s were measured on a mockup of the injection line. The original valve produced flow of $\sim$1$\times$10$^5\,$Torr-l/s when mounted on DIII-D. The new valve is intended to increase the effective risetime of particles delivered to the plasma rather than the total number of particle delivered. It is now on DIII-D undergoing testing under actual tokamak operating conditions to check the opening time in the presence of a magnetic field. Initial experiments of injection into the DIII-D plasma are scheduled for the summer of 2006.