Compact flexible pellet injection system for plasma fueling experiments

A compact pellet injection system has been designed and constructed at the Oak Ridge National Laboratory to provide a flexible fueling system for studies in magnetic confinement fusion devices. The system, referred to as a "pellet injector in a suitcase," is a pipe gun device with a four-barrel capability (1- to 4-mm bore), and it uses a cryogenic refrigerator for in-situ hydrogen pellet formation. The injector design allows for simple change-out of barrel sizes and different pellet acceleration options, including mechanical punches and/or propellant valves to provide speeds in the range of ∼100 to 1500 m/s. The stand-alone instrumentation and controls, as well as the data acquisition system, are personal-computer-based and housed in one standard instrument cabinet. The portable system has been developed to provide a flexible, low-cost fueling system that can be used on a number of plasma confinement experiments with minimal installation and operation costs. The prototype will initially be installed on the Madison Symmetric Torus (MST) at the University of Wisconsin. For the MST application, the pellet sizes will be in the range of 1 to 1.8 mm.