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  • 1
    Electronic Resource
    Electronic Resource
    Measurement and calculation of the efficiency of fission detectors designed to monitor the time dependence of the neutron production of JET (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1093-1095 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Three pairs of fission counters (each pair one 235U and one 238U) are used at the Joint European Torus to determine the time dependence of the neutron production. In order to determine the absolute value of the neutron flux at the detector location it is necessary to know the neutron detection efficiency of the counter assemblies. This was measured using monoenergetic neutrons (at 2.5 and 14 MeV) and Cf and Am/Be sources. The fraction of fissions detected was determined by extrapolation of the pulse-height spectrum to zero pulse height. The calculation of efficiency was made with the Monte-Carlo neutron transport code MORSE. It was found that the detailed structure of the counter significantly affected the calculated efficiency and that the thermal cross-section values of the DLC37F nuclear data library had to be replaced with room-temperature values. The mean difference between calculation and experiment is (5.5±6.3)%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138233
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Neutron spectrometry at JET (invited) (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1717-1722 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Measurements of the energy spectra of fusion neutrons is accorded a prominent position in the neutron diagnostics program at JET. The nature of the information on plasma properties which it is hoped will be obtained is discussed, as is the availability of suitable instruments and techniques for spectrometry on thermonuclear plasmas. Of these instruments, only the 3He ionization chamber has, so far, been successfully exploited; the lessons learned regarding its performance are outlined and the results obtained for ohmically and ICRF-heated plasmas are presented. It is shown that the deuterium ion energy distributions appear to be Maxwellian for all plasmas studied, that central ion temperatures have been obtained on a shot-by-shot basis which agree well with corresponding values obtained by neutral particle analysis and that the deuteron-to-electron density ratio in the plasma is approximately 0.5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138559
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  • 3
    Electronic Resource
    Electronic Resource
    Neutron measurements from the preliminary tritium experiment at JET (invited) : 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. 4511-4516 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A comprehensive range of neutron diagnostics has been installed on the Joint European Torus (JET) for studying deuterium plasma discharges; measurements are made for the 2.5-MeV neutrons emitted from d–d fusion reactions and for the 14-MeV neutrons from t–d burn-up reactions undergone by the 1.0-MeV tritons emitted in the d–d reactions. The time-resolved 2.5-MeV neutron emission is recorded with fission chambers, while the very low intensity 14-MeV neutron emission is recorded with silicon diodes. Absolute calibrations of these measurements are obtained by application of activation techniques. A 19-channel neutron profile monitor provides emissivity profiles for both 2.5- and 14-MeV neutrons independently. Finally, 2.5-MeV neutron energy spectra are recorded with a time-of-flight spectrometer. The recently performed preliminary tritium experiment (PTE) has provided a unique opportunity to test the performance of these neutron diagnostics with deuterium–tritium plasmas, although the time scale from proposal to completion was too short to permit the installation of dedicated instrumentation for the highly intense 14-MeV neutron fluxes. Such instrumentation will be provided for the final, active, phase of JET operation. This presentation will concentrate on the performance of the existing diagnostics during the PTE and will indicate some of the lessons that have been learned regarding neutron measurements for future deuterium–tritium discharges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143707
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  • 4
    Electronic Resource
    Electronic Resource
    The new JET 2.5-MeV neutron time-of-flight spectrometer : 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. 4586-4588 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A major upgrade of the JET 2.5-MeV neutron time-of-flight spectrometer has been completed. The improvement has permitted ion temperature measurements for Maxwellian deuterium plasmas with Ti(approximately-greater-than)4 keV to be obtained in 0.5-s intervals. By combining observations of neutron and x-ray energy spectra with studies of γ-ray emission from reactions between fast deuterons and impurities, the effects of ICRF heating on the deuterium energy distribution have been studied. The time evolution of neutron energy spectra from deuterium-beam heated deuterium plasmas is illustrated and a method for evaluating the ion temperature from such sequences is indicated. Furthermore, the spectrometer has shown stable performance during high neutron fluxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143678
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  • 5
    Electronic Resource
    Electronic Resource
    In-vessel calibration of the JET neutron monitors using a 252Cf neutron source: Difficulties experienced : Eight topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3172-3174 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The most direct method of obtaining an absolute calibration of the set of fission chambers used at JET for the measurement of the time-resolved neutron yield is by means of a standardized 252Cf radio-isotope neutron source which is moved around the vacuum vessel to map out the volume occupied by the plasma. The accuracy of this procedure can approach 10%. However, its applicability depends on the geometry of the tokamak and the location of the fission chambers. At JET, most of the neutrons reach the detectors by passing through the main diagnostic ports. Now that these ports have become surrounded by massive items of hardware, it is found that this equipment moderates and absorbs the 252Cf neutrons more strongly than 2.5 MeV neutrons. This paper examines the magnitude of the errors on the absolute calibration of the fission chambers introduced by this effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141677
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  • 6
    Electronic Resource
    Electronic Resource
    Calibration of the JET neutron yield monitors using the delayed neutron counting technique : Eight topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3178-3180 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The time-resolved neutron yield is routinely measured on the JET tokamak using a set of fission chambers. At present, the preferred technique is to employ activation reactions to determine the neutron fluence at a well-chosen position and to relate the measured fluence to the total neutron emission by means of neutron transport calculations. The delayed neutron counting method is a particularly convenient method of performing the activation measurement and the fission cross sections are accurately known. This paper outlines the measurement technique as used on JET.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141679
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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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  • 8
    Electronic Resource
    Electronic Resource
    Neutron profile measurements for trace tritium experiments : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1123-1125 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The JET neutron profile monitor was used to study the transport of tritium into a magnetically confined deuterium plasma. Trace amounts of tritium were introduced through a gas valve beyond the plasma edge into a variety of plasma confinement regimes. The d(t,n)α fusion cross section is two orders of magnitude greater than the d(d,n)3He cross section and so a puff of tritium which has a negligible effect on the plasma nevertheless produces a large d–t neutron signal. The profile monitor consists of two cameras each made up of a fan-shaped array of collimated lines of sight. It was used to measure the d–d and d–t neutron profiles simultaneously. This article describes the detection system, its operation and assesses the difficulties due to scattered neutrons. The profiles can be used to determine tritium density and transport coefficients. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149330
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  • 9
    Electronic Resource
    Electronic Resource
    A neutron camera for ITER (invited) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 514-519 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Based upon JET experience, the measurement of multichannel collimated neutron fluxes and of the neutron spectrum gives time-dependent information on spatial profiles of neutron emission and alpha–particle birth, the total neutron emission (fuel burn-up rate), plasma position, effects of plasma instabilities, triton burn-up, ion temperature, and fuel densities. The design for a horizontally viewing neutron camera for ITER is based upon the prototype and upgrade versions of the JET neutron emission profile monitor and the JET spectrometers. It is proposed that vertically stacked modules are installed in the ITER biological shield in a fan shaped viewing geometry, aimed at a focal point located at the slit opening of a preshield designed to reduce the streaming neutron flux. Each module contains a pair of sight lines with adjustable collimation, allowing for multiple detector neutron flux monitoring and neutron spectroscopy over a wide operating range. The modular system allows flexibility in detector choice and viewing geometry. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147619
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  • 10
    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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