Deuterium pumping speed measurements on 77 K cryopanels and implications for D-T retention in neutral beam systems
An upper limit for the pumping speed of deuterium on 77 K surfaces has been determined by in-situ pressure measurements in a TFTR neutral beam line pumped by 423 m/sup 2/ of LN/sub 2/-cooled cryopanels. The measurement has importance for estimating the tritium retention in the beam line following operation of the ion sources with tritium. No D/sub 2/ pumping was observed. An upper limit for D/sub 2/ pumping on 77 K surfaces of less than or equal to2.4 x 10/sup -7/ l/s cm/sup 2/ was determined, corresponding to a D/sub 2/ sticking coefficient of less than or equal to1.5 x 10/sup -8/. Based on the upper limit a D-T retention factor, equal to the ratio of retained D-T to D-T input, has been determined to be less than or equal to5 x 10/sup -3/. This upper limit for D-T retention bounds the tritium inventory within the beam line to a small fraction of the tritium throughput. Comparably small upper limits for hydrogenic sticking coefficients, of the order of 10/sup -6/ - 10/sup -10/, have been determined from a review of H/sub 2/O cryotrapping measurements at 77 K and from the physical adsorption studies of H/sub 2/ on H/sub 2/O at 4 K. 22 refs., 5 figs., 1 tab.
- Research Organization:
- Princeton Univ., NJ (USA). Plasma Physics Lab.
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 6582691
- Report Number(s):
- PPPL-2572; CONF-881002-34; ON: DE89004633; TRN: 89-001879
- Resource Relation:
- Conference: 35. national vacuum symposium and 4th international laser science conference, Atlanta, GA, USA, 2 Oct 1988; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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ION SOURCES
PRESSURE MEASUREMENT
THERMONUCLEAR FUELS
TRITIUM
BEAM INJECTION
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
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ODD-ODD NUCLEI
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STABLE ISOTOPES
THERMONUCLEAR REACTORS
TOKAMAK TYPE REACTORS
YEARS LIVING RADIOISOTOPES
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