Control of the D-T gas injection system for TFTR neutral beams

A gas injection system is currently being designed to supply the neutral beam (NB) long pulse ion sources (LPIS) in support of the tritium phase of TFTR (Tokamak Fusion Test Reactor) operation. Each NB source will be supplied by a dual gas injection system. Separate deuterium and tritium gas injection subsystems provide the greatest gas isolation as well as providing redundancy. A single programmable logic controller will provide central control of the D-T gas injection subsystems of all 12 NB sources. To maintain accurate T₂ inventory control, the PLC will accurately monitor the NB T₂ usage. The usage will be correlated with the Tritium Gas Delivery System´s (TGDS´s) information on the quantity of T₂ delivered. Central control will enable an operator to quickly respond to any event affecting the NB tritium subsystems. Individual closed-loop controllers will maintain precise flow control for each LPIS during beam extraction. T₂ or D₂ will be delivered in small batches, to a local plenum on each individual LPIS. A piezoelectric valve, coupled with pressure feedback from the local LPIS gas storage plenum, will be used to establish a controlled bleeddown of the individual gas plenums during injection