A Compact Flexible Pellet Injector for the TJ-II stellarator

A compact multi-barrel pellet injector system is being developed for the TJ-II stellarator. Its design is based on the system currently installed at the MST facility (Univ. Winconsin) and will provide maximum flexibility at minimal cost, while also allowing for future upgrades. It is a four-barrel system destined for use both as an active plasma diagnostic and as a plasma fueling source. In order to achieve both objectives it will be sufficiently flexible to allow frozen hydrogen pellets with diameters from 0.4 to 1 mm to be formed and accelerated to velocities between 100 and 1000 m s-1. However, floor space restrictions and nearest-neighbor considerations limits the overall length to <1.7 m (mechanical punch end to final guide tube interfaces). This will be done by redesigns of the MST gun barrel, vacuum coupling, gas dump and guide tube sectors. Finally, the system is completed by stand-alone instrumentation and controls, as well as Lab View controlled gas manifolds