NEUTRAL ATOM MODELING OF THE TFTR FIRST WALL, PUMP DUCTS, AND NEUTRALBEAMS

The DEGAS neutral transport code is uses in two separate cases to simu late the neutral beam box and vessel of the Tokamak Fusion Test Reacto r (TFTR). For the neutral beam box simulation, known input parameters include the ion density at the source exit and the proportion of input gas that is converted to the high-energy atomic beam. The TO current to the torus is (1.61 +/- 0.03) x 10(20) s(-1), with the high-energy b eam having a median energy above 95 keV. Corresponding results are fou nd for the DO current. In addition, the amount of gas reaching the tor us, the pressure, and the flux and energy distributions of the ions an d neutrals to the walls are found. For the tritium case, it is calcula ted that 92.4 +/- 0.2% of the input tritium reaches the cryopanels, 6. 64 +/- discussed. 0.05% reaches the torus, and 1.0 +/- 0.2% reaches th e ion dump. In the second run, DEGAS was used to calculate the neutral atom flux and energy of particles incident on the walls of the vacuum vessel and the neutral pressure in the pump duct of TFTR during a typ ical supershot with a 50/50 mixture of deuterium-tritium. Output quant ities are the current and energy to the bumper limiter and first wall. The total amount of tritium implanted in the vacuum vessel after 150 shots of 1-s duration is estimated to be 0.5 +/- 0.1 g in the bumper l imiter and 0.042 +/- 0.023 g in the outer wall and pumping duct, which is well within the 5-g On-site inventory and the 2-g in-vessel invent ory. The implications of these results are discussed.