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  • 1990-1994  (18)
  • 1
    Electronic Resource
    Electronic Resource
    Status of the neutron diagnostic experiment for Alcator C-Mod : 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. 4530-4532 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Alcator C-Mod experiment is expected to produce neutrons at a rate of up to 1 × 1016 n/s during its highest performance operation. The global neutron detection system must provide accurate measurement of this production over the full operating regime of the experiment, 1011–1016 n/s. This is accomplished using a series of uranium fission detectors enriched in U235 of staggered sensitivity. These are distributed in two moderator assemblies. A BF3 detector is added to each moderator to cover the lowest operational range. Preliminary calibration of the system has been accomplished using a 65.4 μg Cf252 source placed inside the Alcator C-Mod vacuum vessel. The system design and calibration is discussed herein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143711
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  • 2
    Electronic Resource
    Electronic Resource
    Neutron calibration techniques for comparison of tokamak results (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3501-3504 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A workshop on 1–3 August 1989 reviewed the techniques, uncertainties, and experiences of neutron calibration on PLT, TFTR, JET, Tore Supra, JT-60, JIPPT-IIU, Alcator C-Mod, ATF, FT, ASDEX, Textor, and DIII-D. In the summary session, the workshop participants discussed possible consensus neutron calibration techniques appropriate to D-D plasmas in tokamaks. The application of such techniques would facilitate a more accurate comparison of neutron yields from different devices, and also allow new calibration techniques to relate their precision to a reference value. General agreement was reached on the suitability of two techniques: (1) a 252Cf source calibration of epithermal neutron detectors, and (2) threshold neutron activation of Ni foils placed vertically above or below the plasma. This paper will present details on detector positioning, neutron transport calculations, and interlab normalization needed to accomplish the standardized calibration using a Cf neutron source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141558
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  • 3
    Electronic Resource
    Electronic Resource
    Neutral particle diagnostics for ALCATOR C-Mod : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3119-3121 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The ALCATOR C-Mod experiment will be equipped with two PPPL charge exchange neutral particle analyzers (CENAs), one of which views the plasma tangentially (Rtan/R0=1.05), whereas the second has a horizontally scannable sight line (0≤Rtan/R0≤0.51). The perpendicularly viewing CENA will be capable of analyzing neutrals up to 600 keV amu for up to three separate species simultaneously. Thus high-energy tails can be observed together with the bulk ion temperature. The operation of both analyzers will allow simultaneous measurements from both the perpendicular and tangential chords. The CENAs will be used to study the effect of ICRF heating on the ion energy distribution with emphasis on the high-energy tail. A Fokker–Planck code (FPPRF) [Hammett, Ph.D. thesis, Princeton (1986)] is used to assess the appropriate operating regime of the analyzer (n≤4×1020 m−3 for Ti=2 keV, for Maxwellian ion energy distribution). The experimental design and computer simulations will be detailed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141700
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  • 4
    Electronic Resource
    Electronic Resource
    First results from Alcator-C-MODf| (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1511-1518 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Early operation of the Alcator-C-MOD tokamak [I.H. Hutchinson, Proceedings of IEEE 13th Symposium on Fusion Engineering, Knoxville, TN, edited by M. Lubell, M. Nestor, and S. Vaughan (Institute of Electrical and Electronic Engineers, New York, 1990), Vol. 1, p. 13] is surveyed. Reliable operation, with plasma current up to 1 MA, has been obtained, despite the massive conducting superstructure and the associated error fields. However, vertical disruptions are not slowed by the long vessel time constant. With pellet fueling, peak densities up to 9×1020 m−3 have been attained and "snakes'' are often seen. Initial characterization of divertor and scrape-off layer is presented and indicates approximately Bohm diffusion. The edge plasma shows a wealth of marfe-like phenomena, including a transition to detachment from the divertor plates with accompanying radiative divertor regions. Energy confinement generally appears to exceed the expectations of neo-Alcator scaling. A transition to Ohmic H mode has been observed. Ion cyclotron heating experiments have demonstrated good power coupling, in agreement with theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870701
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  • 5
    Electronic Resource
    Electronic Resource
    Neutron calibration techniques for comparison of tokamak results (abstract) : Eighth topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3232-3232 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A workshop on 1–3 August 1989 reviewed the techniques, uncertainties, and experiences of neutron calibration on PLT, TFTR, JET, Tore Supra, JT-60, JIPPT-IIU, Alcator C-Mod, ATF, FT, ASDEX, Textor, and DIII-D. In the summary session, the workshop participants discussed possible consensus neutron calibration techniques appropriate to D-D plasmas in tokamaks. The application of such techniques would facilitate a more accurate comparison of neutron yields from different devices, and also allow new calibration techniques to relate their precision to a reference value. General agreement was reached on the suitability of two techniques: (1) a 252Cf source calibration of epithermal neutron detectors, and (2) threshold neutron activation of Ni foils placed vertically above or below the plasma. This paper will present details on detector positioning, neutron transport calculations, and interlab normalization needed to accomplish the standardized calibration using a Cf neutron source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141648
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  • 6
    Electronic Resource
    Electronic Resource
    Fast-wave ion cyclotron resonance heating experiments on the Alcator C tokamak (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1657-1670 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper, minority regime fast-wave ICRF (Ion cyclotron range of frequency) heating experiments conducted on the Alcator C tokamak [Nucl. Fusion 26, 1665 (1986)] are described. Up to 450 kW of rf (radio frequency) power at frequency f=180 MHz was injected into plasmas composed of deuterium majority and hydrogen minority ion species at magnetic fields of B0(approximately-equal-to)12 T, densities 0.8≤n¯e≤5×1020 m−3, and minority concentrations 0.25(approximately-less-than)ηH≤8%. Typical ion temperatures were TD(0)∼1 keV, while, depending on density, typical electron temperatures were in the range Te(0)∼1.5–2.5 keV. Central deuterium ion temperature increases of ΔTD(0)=400 eV were observed at n¯e=1×1020 m−3, while significantly smaller ion temperature increases were observed at higher densities. At the highest densities, ion heating became insignificant due in part to a limitation on power handling by the antenna that became more severe with increasing density. Significant electron heating was not observed at any density. Heating of the minority species at low densities indicated severe losses, but at higher densities it was consistent with efficient collisional coupling of the rf power from the hydrogen minority species to the deuterium majority species. Analysis of the deuterium power balance indicated no significant change in the deuterium thermal transport properties as a function of rf power. This may be consistent with the fact that the rf power never exceeded the Ohmic heating (OH) contribution. However, a very strong dependence of the deuterium transport properties on density was observed, and appears to be the dominant process limiting the effectiveness of ICRF heating at high density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859686
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  • 7
    Electronic Resource
    Electronic Resource
    Charged fusion product diagnostics in Alcator C-Mod : 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. 4533-4535 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: With a plasma current of up to 3 MA, toroidal field of up to 9 T, the confinement of the charged fusion products (CFPs) in Alcator C-Mod is expected to be excellent. For example, at maximum current and field, classical losses of the 0.8 MeV 3He, 1 MeV triton, 3 MeV proton, 3.5 and 3.7 MeV alphas are expected to be less than 5%. For the study of the global confinement of CFPs, we plan to measure the burnup of the 1 MeV triton (from the D–D reaction) using a proton recoil detector (NE-213) for the detection of the 14 MeV neutron resulting from the secondary fusion reaction (D–T). On the other hand, loss measurements of CFPs will be made inside the first wall with two detectors (one at the bottom, one at the midplane) using silicon based detectors. The midplane detector will be used to diagnose D–3He plasmas by looking at the unconfined 14.7 MeV proton. In addition to the derivation of fusion yield, energy distribution of the escaping protons will provide information about the ion velocity distribution of the reactants. The bottom detector is time, pitch angle and energy resolved, and thus will be used to study loss mechanisms such as first orbit, toroidal field ripple and magnetohydrodynamics-induced diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143813
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  • 8
    Electronic Resource
    Electronic Resource
    Neutron diagnostic experiment for Alcator C-Mod : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3166-3168 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The neutron production rate on Alcator C-Mod is expected to peak at 1×1016 n/s for the highest performance experimental pulses. Measurement of the total fusion yield is important for both assessing the experiment and for evaluation of radiological data. The neutron detectors must therefore be capable of accurate measurement over a wide operating regime (1011–1016 n/s from the source). This can be achieved with a series of fission detectors (U235 and U238), capable of operating in both a pulsed and current mode. Computer calculations optimizing the placement of these detectors and also the moderator design are detailed. Calibration of this system will be achieved using a Cf 252 source which will be moved on a track continuously around the major axis. It will also be placed discretely at a number of locations in the torus. MCNP calculations will complement the calibration data. Details of the experimental setup and calibration scheme will be presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141675
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of the antimony catalyst remnants on the melt crystallization of PET (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 1997-2001 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The nucleating activity of antimony catalyst remnants on the melt crystallization of poly(ethylene terephthalate) (PET) is proved through comparisons, for samples with Sb concentrations in the range 180-1850 ppm, of the crystallization behaviors before and after a complete extraction of the catalyst remnants. These comparisons are performed by analysis of the crystallization peaks of differential scanning calorimetry (DSC), by the study of the isothermal crystallization kinetics from X-ray diffraction experiments, and by optical microscopy observations of the size of the spherulites. The dependence of the crystallization temperature (Tc, as evaluated by the position of the DSC peak) on the Sb concentration, reported in the literature, is shown to be largely overestimated. In particular, it is found that the Tc of commercial samples are essentially unaffected by the presence of the standard concentrations of Sb catalyst remnants. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070481113
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  • 10
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    Neutron diagnostic experiment for Alcator C‐Mod (1990)
    American Institute of Physics
    Details
    Publication Date: 1990-10-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics
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