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  • 1
    Electronic Resource
    Electronic Resource
    Particle reflection and TFTR neutral beam diagnostics : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4523-4526 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Determination of two critical neutral beam parameters, power and divergence, are affected by the reflection of a fraction of the incident energy from the surface of the measuring calorimeter. On the TFTR Neutral Beam Test Stand, greater than 30% of the incident power directed at the target chamber calorimeter was unaccounted for. Most of this loss is believed due to reflection from the surface of the flat calorimeter, which was struck at a near grazing incidence (12°). Beamline calorimeters, of a "V''-shape design, while retaining the beam power, also suffer from reflection effects. Reflection, in this latter case, artificially peaks the power toward the apex of the "V,'' complicating the fitting technique, and increasing the power density on axis by 10%–20%; an effect of import to future beamline designers. Agreement is found between measured and expected divergence values, even with 24% of the incident energy reflected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143709
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  • 2
    Electronic Resource
    Electronic Resource
    Observation of Doppler shifted Tα emission from TFTR tritium neutral beams : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 632-634 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 195 tritium ion source shots were injected into Tokamak Fusion Test Reactor (TFTR) high power plasmas during December 1993–March 1994. In addition, four highly diagnosed pulses were fired into the calorimeter. Analysis of the Doppler shifted Tα emission of the beam in the neutralizer has revealed that the extracted ion compositions for deuterium and tritium are indistinguishable: 0.72±0.04 D+; 0.22±0.02 D+2; 0.07±0.01 D+3 compared to 0.72±0.04 T+; 0.23±0.02 T+2; 0.05±0.01 T+3. The resultant tritium full-energy neutral fraction is higher than for deuterium due to the increased neutralization efficiency at lower velocity. To conserve tritium, it was used only for injection and a few calorimeter test shots, never for ion source conditioning. When used, the gas species were switched to tritium only for the shot in question. This resulted in an approximately 2% deuterium contamination of the tritium beam and vice versa for the first deuterium pulse following tritium. Data from the calorimeter shots indicate that tritium contamination of the deuterium beam cleans up in five to six beam pulses, and is reduced to immeasurable quantities prior to deuterium beam injection. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146309
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  • 3
    Electronic Resource
    Electronic Resource
    Low Z impurity ion extraction from Tokamak Fusion Test Reactor ion sources (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2729-2736 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Tokamak Fusion Test Reactor (TFTR) deuterium neutral beams have been operated unintentionally with significant quantities of extracted water ions. Water has been observed with an optical multichannel analyzer. These leaks were thermally induced with the contamination level increasing linearly with pulse length. Up to 6% of the beam current was attributed to water ions, corresponding to an instantaneous value of 12% at the end of a 1.5 s pulse. A similar contamination is observed during initial operation of ion sources exposed to air. Operation of new ion sources typically produces a contamination level of ∼2%, with cleanup to undetectable levels in 50–100 beam pulses. Approximately 90% of the water extracted from ion sources with water leaks was deuterated, implying that there is the potential for tritiated water production during TFTR's forthcoming DT operation. It is concluded that isotope exchange in the plasma generator takes place rapidly, most likely as the result of surface catalysis. The primary concern is with O implanted into beam absorbers recombining with tritium, and the subsequent retention of T2O on cryopanels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144411
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  • 4
    Electronic Resource
    Electronic Resource
    Measurement of thermal ion profiles in TFTR neutral beamlines (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3701-3709 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A technique is described whereby the ion dumps inside the TFTR Neutral Beam Test Stand were used to measure thermal profiles of the full-, half-, and third-energy ions. 136 thermocouples were installed on the full-energy ion dump, allowing full beam contours. Additional linear arrays across the widths of the half- and third-energy ion dumps provided a measure of the shape, in the direction parallel to the grid rails, of the half- and third-energy ions, and, hence, of the molecular ions extracted from the source. As a result of these measurements, it was found that the magnet was more weakly focusing, by a factor of 2, than expected, explaining past overheating of the full-energy ion dump. Hollow profiles on the half- and third-energy ion dumps were observed, suggesting that extraction of D+2 and D+3 is primarily from the edge of the ion source. If extraction of half-energy ions is from the edge of the accelerator, a divergence parallel to the grid rails of 0.6°±0.1° is deduced. It is postulated that a nonuniform gas profile near the accelerator is the cause of the hollow partial-energy ion profiles, the pressure being depressed over the accelerator by particles passing through this highly transparent structure. Primary electrons reaching the accelerator produce nonuniform densities of D+2 through the ionization of this gas. D+3 is created through subsequent D+2-gas collisions. A technique of rastering the ion beam across the full-energy dump was examined as a means of reducing the power density. By unbalancing the currents in the two coils of the magnet, on a shot-by-shot basis, by up to a 2:1 ratio, it was possible to move the centerline of the full-energy ion beam sideways by ∼12.5 cm. The adoption of such a technique, with a ramp of the coil imbalance from 2:1 to 1:2 over a beam pulse, could reduce the full-energy ion dump power density by a factor of (approximately-greater-than)1.5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143601
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  • 5
    Electronic Resource
    Electronic Resource
    Temporal behavior of neutral particle fluxes in TFTR neutral beam injectors (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 3721-3729 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Data from an E(parallel)B charge exchange neutral analyzer (CENA), which views down the axis of a neutral beamline through an aperture in the target chamber calorimeter of the TFTR neutral beam test facility, exhibit two curious effects. First, there is a turn-on transient lasting tens of milliseconds having a magnitude up to three times that of the steady state level. Second, there is a 720 Hz, up to 20% peak-to-peak fluctuation persisting the entire pulse duration. The turn-on transient occurs as the neutralizer/ion source system reaches a new pressure equilibrium following the effective ion source gas throughput reduction by particle removal as ion beam. Widths of the transient are a function of the gas throughput into the ion source, decreasing as the gas supply rate is reduced. Heating of the neutralizer gas by the beam is assumed responsible, with gas temperature increasing as gas supply rate is decreased. At low gas supply rates, the transient is primarily due to dynamic changes in the neutralizer line density and/or beam species composition. Light emission from the drift duct corroborate the CENA data. At high gas supply rates, dynamic changes in component divergence and/or spatial profiles of the source plasma are necessary to explain the observations. The 720 Hz fluctuation is attributed to a 3% peak-to-peak ripple of 720 Hz on the arc power supply amplified by the quadratic relationship between beam divergence and beam current. Tight collimation by CENA apertures cause it to accept a very small part of the ion source's velocity space, producing a signal linearly proportional to beam divergence. Estimated fluctuations in the peak power density delivered to the plasma under these conditions are a modest 3%–8% peak to peak. The effects of both phenomena on the injected neutral beam can be ameliorated by careful operation of the ion sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140482
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  • 6
    Electronic Resource
    Electronic Resource
    Operation of a TFTR ion source with a ground potential gas feed into the neutralizer (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1964-1969 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: TFTR long pulse ion sources have been operated with gas fed only into the neutralizer. Gas for the plasma generator entered through the accelerator rather than directly into the arc chamber. This modification has been proposed for tritium beam operation to locate control electronics at ground potential and to simplify tritium plumbing. Source operation with this configuration and with the nominal gas system that feeds gas into both the ion source and the center of the neutralizer are compared. Comparison is based upon accelerator grid currents, beam composition, and neutral power delivered to the calorimeter. Charge exchange in the accelerator can be a significant loss mechanism in both systems at high throughput. A suitable operating point with the proposed system was found that requires 30% less gas than used presently. The extracted D+, D+2, and D+3 fractions of the beam were found to be a function of the gas throughput; at similar throughputs, the two gas feed systems produced similar extracted ion fractions. Operation at the proposed gas efficient point results in a small reduction (relative to the old high throughput mode) in the extracted D+ fraction of the beam from 77% to 71%, with concomitant changes in the D+2 fraction from 18% to 26%, and 6% to 3% for D+3. The injected power is unchanged, ∼2.2 MW at 95 kV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142400
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  • 7
    Electronic Resource
    Electronic Resource
    Progress in the neutral beam injection heating experiment on the Tokamak fusion test reactor
    Amsterdam : Elsevier
    Nuclear Inst. and Methods in Physics Research, B 40-41 (1989), S. 996-999 
    Details
    ISSN: 0168-583X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0168-583X(89)90525-9
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