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  • American Institute of Physics (AIP)  (16)
  • 2020-2024
  • 1990-1994  (11)
  • 1985-1989  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Soft x-ray tomography on the RTP tokamak : Eighth topical conference on high—temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3067-3069 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A soft x-ray tomography system is being constructed for the RTP tokamak. The main aim of this system is to measure fluctuations in the plasma emissivity with relatively high poloidal m number. Five pinhole cameras will be distributed inside the vessel in such a way that it becomes possible to reconstruct modes up to m=4, without making any assumption about the plasma rotation. The system has been designed to obtain a minimum bandwidth of 200 kHz and a temporal resolution of 1 μs. We describe the hardware that is under construction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141729
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  • 2
    Electronic Resource
    Electronic Resource
    Ion temperature measurements in tokamak plasmas by Rutherford scattering (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3359-3368 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.1142553
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  • 3
    Electronic Resource
    Electronic Resource
    Soft x-ray tomography diagnostic at the RTP tokamak (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2295-2305 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An 80-channel soft x-ray tomography system has been constructed for diagnosing the RTP (Rijnhuizen Tokamak Project) tokamak plasma. Five pinhole cameras, each with arrays of 16 detectors are distributed more or less homogeneously around a poloidal plasma cross section. The cameras are positioned close to the plasma edge to enable viewing angles which could not be reached otherwise. The system can be used for making tomographic reconstructions of the soft x-ray emissivity with a relatively high poloidal mode number (up to both components of m=4), which is an improvement with respect to other plasma tomography systems presented in literature. The temporal resolution of the system is 5 μs. Apart from a description of the hardware and geometrical layout of the system, the paper will focus on two important issues, namely the calibration of the detectors and the positioning of the cameras in the vacuum vessel of the tokamak. A dedicated x-ray source has been designed for the relative calibration of the detectors of each individual camera. Misalignment causes several artifacts in tomographic reconstructions obtained with multicamera systems. Therefore, two new methods are proposed which make use of the plasma itself for improving the knowledge about the positions of the cameras.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144680
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  • 4
    Electronic Resource
    Electronic Resource
    H−-conversion aided detection of low-energy H0 fluxes from the TORTUR tokamak in a time-of-flight analyzer (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2223-2231 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A time-of-flight spectrometer has been developed to examine the velocity distribution of the hydrogen charge-exchange particles emitted from the TORTUR tokamak. To investigate the scrape-off layer, the spectrometer has been made sensitive to low-energy hydrogen atoms. This has been done by converting the hydrogen atoms into more easily detectable negative hydrogen ions on a cesiated monocrystalline tungsten surface. This detection technique enables examination of the neutral particle flux in a large energy range (5–2000 eV). Typical examples of time-of-flight spectra recorded during TORTUR discharges will be shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143143
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  • 5
    Electronic Resource
    Electronic Resource
    On the application of the Rutherford-scattering diagnostics to ion temperature measurements (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 3130-3137 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.339363
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  • 6
    Electronic Resource
    Electronic Resource
    The role of small-impact-parameter electron-loss processes on ion temperatures measured by active-beam plasma diagnostics (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 57-63 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The shape of the energy distribution of scattered particles in an active-beam scattering experiment can be influenced considerably by the presence of highly charged impurity ions in the plasma. In this work it is shown theoretically that multiply charged impurities have only a small effect on the scattering distribution at low energies (〈10 keV/amu) and at high energies (〉75 keV/amu). The effect of the impurities is the most pronounced for energies close to 50 keV/amu. The results of the calculations are in good agreement with experimental results at various energies. Extrapolation to higher beam energies leads to the conclusion that the active-beam scattering diagnostics can be applied also in future fusion devices for measuring the local ion temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343375
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of highly charged impurities on ion temperatures measured with active-beam plasma diagnostics (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 780-786 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The presence of highly charged impurity ions in a (tokamak) plasma can be very disturbing if one wants to apply active-beam scattering diagnostics, for instance, for the measurement of the local ion temperature, since it is nearly impossible to separate particles scattered by the main plasma constituent from those scattered by the impurity ions. In this work it is shown, by making use of already published theoretical results of the electron-loss probability as a function of impact parameter, that not only for H, but also for He injected neutrals, the effect of impurity ions on the relevant energy distribution of scattered neutrals is negligible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339732
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  • 8
    Electronic Resource
    Electronic Resource
    Measurement of ion temperatures by means of Rutherford scattering of energetic neutrals above the limiting angle (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 468-473 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A technique to measure the ion temperature in a thermonuclear plasma is proposed, based on Rutherford scattering of a beam of energetic neutral particles by the plasma ions. If the mass of the beam particles, mb, is larger than the mass of the scattering ions, mp, a sharp maximum (limiting) angle θlim=sin−1(mp/mb) exists in case the thermal velocities of the plasma ions are neglected. When the scattering ions have thermal velocities, however, scattering of beam particles can occur through angles larger than θlim. Measurement of the intensity of particles above the limiting angle can be used to find the temperature of the plasma ions, with a 10% accuracy and a spatial and temporal resolution of 10 cm and a few μs, respectively, provided the ion velocity distribution is Maxwellian. A feasibility study elucidates that this method can also be used to measure the temperature of a 3He minority component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343128
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  • 9
    Electronic Resource
    Electronic Resource
    An electrostatic time-of-flight analyzer for simultaneous energy and mass determination of neutral particles (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 110-117 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.1142317
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  • 10
    Electronic Resource
    Electronic Resource
    Multichannel interferometer/polarimeter system for the RTP tokamak : Eighth topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2882-2884 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A nine-channel interferometer/polarimeter system is designed for the RTP tokamak (Rijnhuizen Tokamak Project, a =0.16 m, R =0.72 m, BT =2.5 T, Ip ≤ 200 kA, and plasma pulse duration 200 ms). A CO2-pumped dual-cavity FIR laser system is used to obtain two FIR laser beams of λ =432 μm with a frequency difference of 1 MHz. The FIR beams are expanded by a set of parabolic mirrors. Corner-cube mixers with Schottky diodes are used as detectors. The mixers are mounted on a linear rail system, such that their positions can be easily changed. The interferometer can be operated with a maximum of 19 channels, and will be extended with a polarimeter to measure the poloidal magnetic field distribution. It will be tried to increase the accuracy of the polarimeter by modulating the polarization of the incoming beam. A scheme for polarization modulation which is based on the idea of Dodel and Kunz will be presented in this paper. This scheme has the advantage that only one set of detectors is needed to measure the electron density and current density. The complete system will be presented along with some pilot experiments concerning the polarization modulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141814
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