Development of a check valve for two-stage pellet injectors

The two-stage light gas gun is presently the most suitable method for injecting solid deuterium pellets at velocities in excess of 2000 m/s. However, the use of this technique in plasma machines presents some drawbacks: (1) the relatively large mass of propellant, which is of the same order of the pellet mass (2) the shape of the pressure pulse, which does not provide an optimum acceleration, unless the pellet is forced in the barrel, providing a sufficient breakout pressure. These problems can be solved completely or in part, by interposing between the pump tube and the barrel a check valve with a suitable opening pressure. In this work a check valve developed at CNPM is described and experimental results are reported.