Experiments with the CNPM gas gun for minimizing piston wear and propellant gas flow

Among the different methods of pellet injection for Tokamak refueling, the two-stage gun is presently the most suitable for pellet speeds over 2000 m/s, but for continuous operation two main problems are to be solved: wear of the pistons and plasma contamination by the propulsion gas. An experimental program is under way with the CNPM two-stage gas gun aimed at the solution of these problems. Different piston geometries and materials have been tested. Moreover, a fast valve has been installed at the exit of the launch barrel, in order to minimize the propellant gas flow. Results of the tests are presented.