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  • 1
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A neutral particle energy analyzer has been developed to measure both the energy and the mass of the incoming particles with only one array of detectors. Energy analysis is performed by means of deflection in an electrostatic field. The mass of the particle is determined by measuring the flight time from a stripping foil to a channel electron multiplier in the focal plane of the analyzer. The application of a stripping foil instead of a gas cell increases the stripping efficiency and simplifies the vacuum system. Monte Carlo simulation studies and first calibration experiments show that the analyzer can be used even at energies down to 1 keV, as long as the stripping foil does not exceed a thickness of 2.0 μg/cm2. These simulations take into account the angular and energy straggling processes that take place in the foil. A triple-coincidence technique can be applied to decrease the sensitivity of the analyzer to neutron and gamma background radiation considerably, as will be shown by calculations.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Rutherford scattering diagnostic has been applied at the TEXTOR tokamak to obtain spatially and temporally resolved information on the temperature of the bulk ions in the plasma. In the experimental setup, a helium atomic beam (30-keV, 12-mA equivalent current) passes vertically through the plasma core. A small part of the injected atoms is scattered elastically by the thermally moving plasma ions. The ion temperature in the scattering volume can be determined from the broadening of the energy spectrum of the scattered particles. Energy analysis of the scattered atoms is performed by a mass-selective time-of-flight analyzer detecting the particles at an observation angle which is selectable between 3° and 8°. Coincidence techniques have been successfully applied in this detector for rejection of background events triggered by detections of neutrons and gamma radiation. Ion temperature profiles were measured on a shot-to-shot basis by shifting the cross section of the diagnostic beam and the observational volume of the analyzer through the plasma. The ion temperatures measured in ohmic deuterium plasmas were found to be in reasonable agreement with those obtained from passive neutral particle analysis. Up to now, ion temperatures have been measured throughout the complete discharge with an accuracy of 8% and a time and space resolution of 100 ms and 0.10 m at a scattering angle of 7°. Deuteron density profiles could be deduced from the scattering yield measured at different radial positions in the plasma. The ratio of the isotopes, hydrogen and deuterium, was determined from their separate contributions to the spectrum of helium particles scattered on hydrogen and deuterium. Although theoretical predictions showed that the majority of the probing helium atoms loses one of its electrons during the elastic scattering process on multiply charged carbon and oxygen ions, contributions from impurities to the observed experimental spectrum are shown to appear dominant for impure plasmas.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 1978-1987 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A mass-discriminating neutral particle spectrometer has been developed for the Rutherford scattering diagnostic at the TEXTOR tokamak. The analyzer is equipped with a momentum preselector and a triple-coincidence time-of-flight detection system providing a rejection capability for background events. Entering neutral particles are stripped by means of a thin carbon foil. Electrons emitted from a second carbon foil are used to give the time-zero signal. Calibration has been performed for hydrogen and helium particles in the energy range from 10 to 90 keV. The energy loss inside the carbon foils, the absolute efficiency, and the resolution of the analyzer have been investigated. The momentum preselector has a bandwidth of ±12.5% with respect to its adjustable central momentum. For both hydrogen and helium, the energy resolution is 2.5% for energies above 30 keV. Calculations show that the analyzer can still operate in the highly radiative environments of nuclear fusion devices.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 3130-3137 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The feasibility for application of small-angle Rutherford scattering of fast neutrals by plasma ions as a possible ion-temperature diagnostic is investigated for a medium-sized tokamak. The analysis is based on elastic scattering of helium atoms from a 20–40 keV and 10 A m−2 probing beam, which are subsequently recorded by a time-of-flight spectrometer with high-energy resolution. Calculations show that the ion temperature can be measured with a 10% accuracy within 1 ms and with a spatial resolution of about 0.1 m. The possible influence of highly charged impurity atoms on the accuracy of the determined temperature value has been closely examined and appears to be negligible at the chosen set of parameters. The good spatial and temporal resolution make the method very suitable to determine the energy deposition profiles in case localized heating is applied to the plasma.
    Type of Medium: Electronic Resource
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