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  • 1
    Electronic Resource
    Electronic Resource
    Collimated ZnS (Ag)-detector array for Tokamak Fusion Test Reactor neutron source strength radial profile measurements (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1081-1083 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Time-resolved radial profile measurements of neutron source strength and Ti are required to determine ion energy balance especially during sawtooth oscillations and adiabatic compression. We describe the Tokamak Fusion Test Reactor (TFTR) vertical multichannel (10) collimator, two channels of which are now being completed. ZnS detectors will be used (Bicron 720) to reject γ rays and scattered neutrons, and operated in both count rate and current modes. The frequency response is limited by counting statistics and sampling times, but resolves compression times (approximately-equal-to)15–30 ms and Ti collapse times during sawtooth (approximately-equal-to)2–3 ms. The collimator consists of the 6-ft test cell floor plus ∼2-ft detector shield. Detector cross talk is calculated to be negligible. The dynamic range of the detectors is (approximately-greater-than)106, covering the range from ohmically heated deuterium (2.5 MeV neutron emissions of (approximately-greater-than)1013 s−1) to deuterium-beam heated tritium plasmas (14 MeV, (approximately-less-than)1019 s−1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138229
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of neutron energy spectrum on the efficiency calibration of epithermal neutron detectors (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1084-1086 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The 235U epithermal neutron fission detector system at TFTR has been calibrated in situ, using three different neutron sources: 252Cf, a D-D, and a D-T neutron generator. These sources produced a continuous spectrum, a line spectrum at ∼2.5 MeV, and a line spectrum at ∼14 MeV, respectively. The toroidally averaged detection efficiencies are 4.61×10−9 (252Cf), 4.80×10−9 (D-D), and 5.42×10−9 (D-T) counts/neutron for a moderated 1.3-g 235U detector placed ∼4 m from the torus centerline. The effects of (n,2n) and (n,n'γ) reactions are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138230
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    TFTR epithermal neutron detector system: Recalibration and effect of nonisotropic neutron emission (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1682-1684 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The primary TFTR neutron source strength measurement system consists of seven fission detectors previously calibrated with D–D and D–T neutron generators and a 252Cf neutron source inside the TFTR vacuum vessel. A recalibration became desirable because of the addition of major components to the tokamak. The new calibration with the D–D neutron generator in situ is consistent with the detection efficiencies measured in the previous calibrations, within the uncertainties. Effects of the anisotropic emission of the neutron generator, due both to the variation of the differential D–D yield with angle (similar to that from beam–target and beam–beam reactions in the beam-driven TFTR plasma) and to scattering and absorption by the generator heads have been observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140132
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  • 4
    Electronic Resource
    Electronic Resource
    Relative intensities of 2.5- and 14-MeV source neutrons from comparative responses of U-238 and U-235 detectors (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1688-1690 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The response of polyethylene-moderated U-235 fission counters is only weakly dependent on incident neutron energy, while the response of unmoderated U-238 or Th-232 fission counters increases strongly with energy. A given concentration of D–T neutrons in a mixed DT–DD source results in a unique relative detector response that depends on the parameters R14 and R2.5, where R14 is the ratio of the unmoderated U-238 and moderated U-235 detector efficiencies for a pure 14-MeV neutron source, and R2.5 is the corresponding ratio for a pure 2.5-MeV source. We have recently determined R14 and R2.5 using D–D and D–T neutron generators inside the TFTR vacuum vessel. The results indicate that, for our detector geometry, the ratio of U-238 to U-235 count rates should increase by a factor of about 3 when the fusion neutron source changes from pure D–D to pure D–T. This calibration is being applied to recent TFTR "supershot'' data, where the uncollided neutron flux in the postbeam phase contains a high proportion of D–T neutrons from the burnup of D–D tritons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140134
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  • 5
    Electronic Resource
    Electronic Resource
    Silicon surface barrier detector for fusion neutron spectroscopy (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1763-1765 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The usefulness of the intrinsic 28Si(n,α)25Mg and 28Si(n, p)28Al reactions in silicon surface barrier detectors for measurements of ion temperatures in D-T fusion plasmas and of D-T fusion neutron flux has been investigated. For a 14-MeV neutron-generator narrow-energy-line source, the energy resolution (∼1.5%), detection efficiency, and useful count rates have been determined. Based on these results, for a 100-ms time bin, D-T plasma ion temperatures from 2 to 6 keV can be determined from the full-width half-maximum (FWHM) of the neutron-induced α spectral lines, with the error estimated to be 25% to 5%, respectively. The maximum intrinsic detection efficiency for a nominal 1500-μm-thick detector is ∼6×10−4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139174
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  • 6
    Electronic Resource
    Electronic Resource
    Neutron diagnostics on TFTR utilizing the Campbelling technique (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1754-1756 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Modified commercial equipment installed on the tokamak fusion test reactor (TFTR) at Princeton Plasma Physics Laboratory (PPPL) utilizes Campbell's mean square voltage theorem to monitor the neutron source strength at neutron count rates orders of magnitude above the capability of the count rate mode. Campbelling uses the large amplitude fluctuations from neutron fission events in the detectors to discriminate against small amplitude γ ray and other noise events. Source strengths yielding equivalent count rates a factor of 5 greater than possible in the conventional count rate mode have been obtained to date. The concept of Campbelling is discussed and the particular application to TFTR is illustrated. Fundamental advantages are the extended useful range of the detectors by a factor of ∼104 and gamma rejection by a factor of ∼103. Some results are shown and the neutron source strengths obtained are compared to those from conventional counting circuits and from other detectors whose outputs have not yet suffered counting losses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139171
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  • 7
    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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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    In situ calibration of TFTR neutron detectors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1900-1914 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report results of the TFTR fission detector calibration performed in December 1988. A NBS-traceable, remotely controlled 252Cf neutron source was moved toroidally through the TFTR vacuum vessel. Detection efficiencies for two 235U detectors were measured for 930 locations of the neutron point source in toroidal scans at 16 different major radii and vertical heights. These scans effectively simulated the volume-distributed plasma neutron source and the volume-integrated detection efficiency was found to be insensitive to plasma position. The Campbell mode is useful due to its large overlap with the count rate mode and large dynamic range. The resulting absolute plasma neutron source calibration has an uncertainty of ±13%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141115
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    Paper (German National Licenses)
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  • 9
    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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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Absolute calibration of neutron detection systems on TFTR and accurate comparison of source strength measurements to transport simulations (invited) : Eighth topical conference on high—temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3151-3156 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Accurate, absolutely calibrated measurements of the neutron source strength are needed for determining the quality of plasma performance, for constraining transport analysis, and for studying fast ion physics such as triton burnup. Obtaining an accurate calibration involves more than performing in situ source calibrations. Efforts on TFTR illustrate the additional need for careful detector characterization, periodic renormalization, and proper cross calibration of less sensitive detectors. Multiple detector systems have been developed on TFTR to provide redundancy and a range of energy sensitivity and time resolution. Three independently calibrated systems now agree in their determination of source strength within relative uncertainties of 15%–20%. These accurate neutron measurements can be effectively used to constrain transport simulations of neutral beam injection and test the modeling and simulation assumptions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141671
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