Time Resolved Deposition Measurements in NSTX

Skinner, C.H. ; Kugel, H. ; Roquemore, A.L. ; Hogan, J. ; Wampler, W.R. ; team, the NSTX

Princeton University. Plasma Physics Laboratory.

关键词: Probability;    Quartz;    Monte Carlo Methods;    Tritium Monte Carlo Methods;    Oxygen;   

DOI  :  10.2172/828594
RP-ID  :  PPPL-3991
RP-ID  :  AC02-76CH03073
RP-ID  :  828594

美国|英语

来源: UNT Digital Library

【 摘 要 】

Time-resolved measurements of deposition in current tokamaks are crucial to gain a predictive understanding of deposition with a view to mitigating tritium retention and deposition on diagnostic mirrors expected in next-step devices. Two quartz crystal microbalances have been installed on NSTX at a location 0.77m outside the last closed flux surface. This configuration mimics a typical diagnostic window or mirror. The deposits were analyzed ex-situ and found to be dominantly carbon, oxygen, and deuterium. A rear facing quartz crystal recorded deposition of lower sticking probability molecules at 10% of the rate of the front facing one. Time resolved measurements over a 4-week period with 497 discharges, recorded 29.2 {micro}g/cm{sup 2} of deposition, however surprisingly, 15.9 {micro}g/cm{sup 2} of material loss occurred at 7 discharges. The net deposited mass of 13.3 {micro}g/cm{sup 2} matched the mass of 13.5 {micro}g/cm{sup 2} measured independently by ion beam analysis. Monte Carlo modeling suggests that transient processes are likely to dominate the deposition.