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  • 1
    Electronic Resource
    Electronic Resource
    Doppler-shifted neutral beam line shape and beam transmission (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 130-138 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Analysis of Doppler-shifted Balmer-α line emission from the Tokamak Fusion Test Reactor's (TFTR) neutral beam injection systems has revealed that the line shape, which is a direct measure of the velocity distribution function, is well approximated by the sum of two Gaussians, or, alternatively, by a Lorentzian. For the sum of two Gaussians, the wide-divergence part of the distribution contains 40% of the beam power and has a divergence five times that of the narrow part. Assuming a narrow 1/e-divergence of 1.3° (based on fits to the beam shape on the calorimeter), the wide part has a divergence of 6.9°. The entire line shape is also well approximated by a Lorentzian with a half-maximum divergence of 0.9°. Up to now, most fusion neutral beam modelers have assumed a single Gaussian velocity distribution, at the extraction plane, in each direction perpendicular to beam propagation. This predicts a beam transmission efficiency from the ion source to the calorimeter of 97%. Waterflow calorimetry data, however, yield a transmission efficiency of ∼75%, a value in rough agreement with predictions of the two Gaussian or Lorentzian models presented here. The broad wing of the two Gaussian distribution also accurately predicts the loss in the neutralizer. An additional factor in determining the power density at the surface of beam absorbers is the angle at which the particles arrive. Angles are different for particles emitted from different locations on the ion source. To treat this situation, the average angle of incidence is calculated. For beam loss at the exit of the neutralizer, the average angle of incidence is 2.2°, rather than the 4.95° subtended by the center of the ion source. This average angle of incidence is found to be a function of beam divergence. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145277
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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and antitumor activity of new platinum complexes (1982)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 25 (1982), S. 952-956 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00350a013
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of density and predation on Scaphiopus couchi tadpoles in desert ponds (1987)
    Springer
    Oecologia 71 (1987), S. 301-307 
    Details
    ISSN: 1432-1939
    Keywords: Desert toads ; Tadpole predation ; Scaphiopus couchi ; Tadpole density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of density on growth and development of Scaphiopus couchi tadpoles in desert ponds were investigated, and sources of mortality over a three-year period were documented. In 16 of the 82 ponds monitored, predation was the principal cause of death, demonstrating that tadpoles in desert ponds may be exposed to high levels of predation, although the overall importance of predation is less here than in more mesic areas. Desiccation was the primary cause of mortality in 49 ponds. Growth and development were extremely slow in most high density ponds and as a result most tadpoles were unable to metamorphose before ponds dried. Only 8 ponds produced metamorphs, and mortality was high even in these. Food-supplementation resulted in some metamorphosis in high density ponds, although the effect was diminished by the extreme crowding in most ponds. In low density ponds, S. couchi tadpoles can develop very quickly and metamorphose. High mortality due to desiccation is largely a consequence of high density: tadpoles rarely completed development in high density ponds, regardless of pond duration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377299
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  • 8
    Electronic Resource
    Electronic Resource
    The characterization of plasma-sprayed/rapid omnidirectional compaction — processed tantalum coatings as applied to densified ceramic substrates (1993)
    Springer
    Journal of materials science 28 (1993), S. 482-488 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The application of rapid omnidirectional compaction (ROC) processing to plasma-sprayed tantalum coatings in order to produce dense wear-resistant tantalum carbide coatings on a variety of predensified ceramic substrates is reported. Substrate materials included aluminium nitride, silicon carbide, silicon nitride, and WC-6Co. In particular, the phase chemistry which evolves during ROC processing, the surface morphology of the coating as-deposited and after ROC processing, and the erosive wear resistance of the coatings, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357827
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  • 9
    Electronic Resource
    Electronic Resource
    Silicon nitride ceramics with celsian as an additive (1996)
    Springer
    Journal of materials science 31 (1996), S. 150-156 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Four different Si3N4 ceramics using 10 wt% celsian (BaAl2Si2O8) as an additive, have been prepared by hot pressing. Different celsian sources and hot-pressing conditions were used and their effects on densification, in situ crystallization of celsian, α to β phase transformation, microstructures and properties, were examined. The use of a presynthesized celsian as a raw material was found to enhance the rates of densification and phase transformation due to the excess silica from raw Si3N4 powders which, however, did not change the microstructure and crystallization behaviour of celsian. Increases in hot-pressing temperatures and times increased the total number of large elongated β grains and resulted in coincidental increases in strength and toughness until the α to β transformation was complete. An intermediate quench-and-reheat step during hot pressing made the microstructure finer and more uniform by greatly reducing the large-sized elongated β grains. The quenching step also disrupted complete crystallization of celsian which led to more grain-boundary glassy phase and compromised the material's high-temperature properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00355139
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  • 10
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    15-Hydroxyprostaglandin dehydrogenase is an in vivo suppressor of colon tumorigenesis (2006)
    National Academy of Sciences
    Details
    Publication Date: 2006-07-31
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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