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Title: Time Resolved Deposition Measurements in NSTX

Abstract

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.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab., Princeton, NJ (US)
Sponsoring Org.:
USDOE Office of Science (SC) (US)
OSTI Identifier:
828594
Report Number(s):
PPPL-3991
TRN: US0404037
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 3 Aug 2004
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CARBON; CONFIGURATION; DEPOSITION; DEUTERIUM; ION BEAMS; MAGNETIC SURFACES; MICROBALANCES; MIRRORS; OXYGEN; PROBABILITY; QUARTZ; RETENTION; SIMULATION; TRANSIENTS; TRITIUM; MONTE CARLO METHODS; PLASMA-WALL INTERACTION; TOKAMAKS, NSTX

Citation Formats

Skinner, C H, Kugel, H, Roquemore, A L, Hogan, J, Wampler, W R, and the NSTX team. Time Resolved Deposition Measurements in NSTX. United States: N. p., 2004. Web. doi:10.2172/828594.
Skinner, C H, Kugel, H, Roquemore, A L, Hogan, J, Wampler, W R, & the NSTX team. Time Resolved Deposition Measurements in NSTX. United States. doi:10.2172/828594.
Skinner, C H, Kugel, H, Roquemore, A L, Hogan, J, Wampler, W R, and the NSTX team. Tue . "Time Resolved Deposition Measurements in NSTX". United States. doi:10.2172/828594. https://www.osti.gov/servlets/purl/828594.
@article{osti_828594,
title = {Time Resolved Deposition Measurements in NSTX},
author = {Skinner, C H and Kugel, H and Roquemore, A L and Hogan, J and Wampler, W R and the NSTX team},
abstractNote = {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.},
doi = {10.2172/828594},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2004},
month = {8}
}