Conceptual design of the vacuum pumping system for the Tokamak Physics Experiment

The conceptual design of the TPX vacuum pumping system is presented. The baseline concept includes a high vacuum pumping system, a roughing and backing system, volume pumping ducts, a leak detection system, a diagnostic pumping system, and a cryostat pumping system. The high vacuum pumping system will initially evacuate the torus, provide pumping of the diverters during operation, and provide pumping for glow discharge cleaning. The high vacuum pumping system has high throughput and variable conductance capabilities and includes cryocondensation pumps for pumping deuterium during normal operation as well as turbomolecular pumps for pumping helium and for glow discharge cleaning. Sixteen vacuum ducts extend from the vacuum vessel through the cryostat to the pumping system; each duct contains a torus isolation valve and an electrical break. Butterfly valves at the cryopump inlets will be used for throttling the pumps and for pump regeneration. In this way, half of the pumps can be regenerated while the others are operating. The specific design parameters and predicted performance of the vacuum pumping system are discussed, as are the upgrade options for steady state and DT operation.