Vacuum and fueling systems for the IGNITEX experiment

Abstract

Results of preliminary studies of the vacuum and fueling requirements for the proposed fusion ignition experiment IGNITEX are discussed. The vacuum system must provide sufficient pumping speed to reach a base pressure of about 10/sup -8/ torr to produce a clean environment for plasma formation. In addition, the pumping speed should meet the requirements of the discharge cleaning cycle. Initial estimates indicate that a pumping speed of about 1500 l/s will be adequate. Two different types of pumping systems, turbomolecular pumps and cryogenic pumps, have been considered. The fueling method will affect the profile of the plasma density, which in turn modifies the energy confinement and the plasma reactivity. Gas puffing can produce flattened density profiles, reducing energy confinement. More peaked density profiles can be provided by a pellet injection fueling system or by operation with reduced gas puffing. However, for the temperature and density regimes expected in the IGNITEX experiment, penetration of the pellets to the central regions of the plasma may be difficult to achieve. The practicality of a pellet injection system for high-density, high-temperature plasmas is being explored. The possibility of inducing high-density plasma breakdown by resonant cavity modes as a means of producing peaked density profiles is also being explored. >