Low Z impurity ion extraction from TFTR ion sources
TFTR deuterium neutral beams have been operated unintentionally with significant quantities of extracted water ions. Water has been observed with an Optical Multichannel Analyzer (OMA) during beam extraction when small water leaks were present within the arc chamber. These leaks were thermally induced with the contamination level increasing linearly with pulse length. 6% of the beam current was attributed to water ions for the worst leak, corresponding to an instantaneous value of 12% at the end of a 1.5 s pulse. A pre-calorimeter collimator was damaged as a result of this operation. A similar contamination is observed during initial operation of ion sources exposed to air. This latter contamination is attributed to the synthesis, from adsorbed air, of either D[sub 2]O or the indistinguishable ND[sub 3]. Initial operation of new ion sources typically produces a contamination level of [approximately]2%. These impurities are reduced to undetectable levels after 50 to 100 beam pulses. Once a water molecule is present in the plasma generator, it is predominantly ionized rather than dissociated, resulting in the extraction of only trace amounts of hydrogenated ions. The addition of water to the extracted beam also reduces the optimum perveance, moving the typical underdense operating point closer to optimum, causing the frequency of grid faults to increase. Close to 90% of the water extracted from ion sources with water leaks was deuterated, implying that the potential exists for the production of tritiated water during TFTR's forthcoming DT operation. Isotope exchange in the plasma generator takes place rapidly and is believed to be surface catalyzed. The primary concern is with O implanted into beam absorbers recombining with tritium, and the subsequent hold up of T[sub 2]O on cryopanels. Continuous surveillance with the OMA diagnostic during DT operation will ensure that ion sources with detectable water are not operated with tritium.
- Research Organization:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 6867280
- Report Number(s):
- PPPL-2897; ON: DE93011978
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Fu
ION SOURCES
PLASMA IMPURITIES
NEUTRAL ATOM BEAM INJECTION
TFTR TOKAMAK
BEAM EXTRACTION
LEAKS
MULTI-CHANNEL ANALYZERS
TRITIUM
WATER
BEAM INJECTION
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CLOSED PLASMA DEVICES
ELECTRONIC EQUIPMENT
EQUIPMENT
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
IMPURITIES
ISOTOPES
LIGHT NUCLEI
NUCLEI
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
PULSE ANALYZERS
RADIOISOTOPES
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
YEARS LIVING RADIOISOTOPES
700460* - Fusion Technology- Heating & Fueling Systems
Fuels- (1992)