Abstract
A compact pellet injector is being built for the TJ-II stellarator. It is an upgraded version of the
“pellet injector in a suitcase” developed at Oak Ridge National Laboratory and installed on the
Madison Symmetric Torus where it continues to be used in many plasma experiments. The design
aim is to provide maximum flexibility at minimal cost, while allowing for future upgrades. It is a
four-barrel system equipped with a cryogenic refrigerator for in situ hydrogen pellet formation, a
combined mechanical punch/propellant valve system, pellet diagnostics, and an injection line,
destined for use as an active diagnostic and for fueling. In order to fulfill both objectives it will be
sufficiently flexible to permit pellets, with diameters from 0.4 to 1 mm, to be fabricated and
accelerated to velocities from 150 to 1000 m s−1.
