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  • 1985-1989  (55)
  • 1
    Electronic Resource
    Electronic Resource
    High-resolution bent-crystal spectrometer for the ultrasoft x-ray region (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 895-906 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multichannel vacuum Bragg-crystal spectrometer has been developed for high-resolution measurements of the line emission from tokamak plasmas in the wavelength region between 4 and 25 A(ring). The spectrometer employs a bent crystal in Johann geometry and a microchannel-plate-intensified photodiode diode array. The instrument is capable of measuring high-resolution spectra (λ/Δλ≈3000) with fast time resolution (4 ms per spectrum) and good spatial resolution (3 cm). The spectral bandwidth is Δλ/λ0=15% at λ0=8 A(ring). A simple tilt mechanism allows access to different wavelength intervals. In order to illustrate the utility of the new spectrometer, time- and space-resolved measurements of the n=3–2 spectrum of selenium from the Princeton Large Torus tokamak plasmas are presented. The data are used to determine the plasma transport parameters and to infer the radial distribution of fluorinelike, neonlike, and sodiumlike ions of selenium in the plasma. The new ultrasoft x-ray spectrometer has thus enabled us to demonstrate the utility of high-resolution L-shell spectroscopy of neonlike ions as a fusion diagnostic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140341
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  • 2
    Electronic Resource
    Electronic Resource
    Fast multichannel electron temperature diagnostic for TFTR using x-ray imaging (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 827-829 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The TFTR x-ray imaging system (XIS) is an array of 64-Si surface barrier diodes which image the plasma poloidally. Special absorber foils have been installed to permit measurement of electron temperature Te with 〈100-μs time resolution along 10–30 chords. The technique uses the ratio of x-ray fluxes transmitted through two different foils, which depend mainly on Te. Simulations show that strong line radiation can change this ratio. To correct for these effects, special beryllium–scandium filters are employed to select the line-free region between 2 and 4.5 keV. Separate filter pairs allow correction for strong L line radiation as well as Ti or Ni Kα emission. The Te determination is based on simulations. Comparison of results with Te values from the electron–cyclotron emission and x-ray pulse height analysis diagnostics is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138186
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  • 3
    Electronic Resource
    Electronic Resource
    Measurements of radial profiles of the ion temperature and the plasma rotation velocity with the TFTR vertical x-ray crystal spectrometer (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1852-1852 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The TFTR vertical x-ray crystal spectrometer has now been operating with three crystals and position-sensitive detectors according to the original design specifications. The observed spectra of heliumlike Ti xxi, Cr xxiii, Fe xxv, and Ni xxvii have permitted a detailed comparison with the predictions from atomic theories, and they have provided data on the radial profiles of the ion temperature and toroidal rotation velocity, as well as the radial ion charge-state distribution in TFTR discharges. Central ion temperatures of 20 keV and central plasma rotation velocities of 5×105 m/s have been recorded from plasmas with auxiliary neutral beam heating. These experimental results are presented. Also discussed are further instrumental improvements, such as the installation of two additional crystals and detectors and the installation of γ and neutron shielding, which will make it possible to measure under full DD and DT operation with 27 MW of neutral beam injection where neutron production rates of 1019 neutrons/s are expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140086
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  • 4
    Electronic Resource
    Electronic Resource
    Tokamak Fusion Test Reactor x-ray imaging diagnostic (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 830-832 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An array of 64 silicon surface-barrier diodes on a circular arc view Tokamak Fusion Test Reactor (TFTR) plasmas through a slot aperture to provide poloidal imaging of x-ray emission in the 200 eV–15 keV range. Information is inferred on magnetohydrodynamic (MHD) instabilities, disruptions, radiation, impurity transport, electron temperature, and electron thermal conductivity. Spatial resolution is 2.5 cm. Movable absorber foil arrays provide energy selection. Preamplifier–amplifier pairs have gains of 0.05–100 V/μA. Two outputs are provided with (1) 40-, 80-, and 300-Hz and (2) 40-, 80-, and 600-kHz filtering. The signals are digitized at rates up to 500 kHz and stored in 128K (total system) memory. Foils, gains, and filters are selectable from the control room by a computer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138187
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  • 5
    Electronic Resource
    Electronic Resource
    Tokamak Fusion Test Reactor prototype x-ray pulse-height analyzer diagnostic (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 840-842 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The x-ray pulse-height analysis (PHA) diagnostic uses a liquid-nitrogen cooled array of 5 Si(Li) and one HpGe detectors to do time-resolved (5–100 ms) x-ray spectroscopy of the central horizontal chord of the Tokamak Fusion Test Reactor (TFTR) plasmas in the 1–50-keV range. Central electron temperature Te and concentration of medium and low-Z impurities are derived from the spectra. Remotely selectable absorber-foil arrays provide selection of the energy range. Fixed and movable aperture arrays allow approximate equalization of count rates in different energy bands and extend dynamic range. Amplifier pulse shapes are approximately triangular. Main amplifier peaking time is 4 μs yielding 230-eV FWHM at 5.9 keV. Pileup inspection times are selectable at 0.13, 0.4, or 0.9 μs. Throughput is up to 42 kHz. The PHA has been used to study temperature and impurities over a wide range of TFTR operational parameters. Dramatic variations in metal impurities with density, plasma current, and major radius have been observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138517
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  • 6
    Electronic Resource
    Electronic Resource
    Measurement of the wall radiation in soft x-ray region in PDX (abstract) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 847-847 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A detector setup with three LN-cooled Si(Li) diodes is used to measure soft x-ray spectra (0.8–20 keV) emitted from the inside walls of the PDX vessel during the plasma discharge. The setup is part of a pulse-height-analysis system, which is used to measure the plasma and wall radiation simultaneously at five different radial positions. The wall and the plasma radiation are measured under different plasma conditions (e.g., OH and neutral beam heating). The wall radiation is very much increased during the neutral beam heating, with an enhancement factor of at least 10 over the OH wall radiation. Since we measure the plasma and the wall radiation at the same time, the measurements allow the conclusion that the wall radiation can be attributed essentially to fluorescence (line radiation, e.g., Ti-Kα) and scattering (continuum part of the wall radiation spectrum). The fluorescence and the scattering are both caused by soft x-ray radiation flux coming from the plasma. There seems to be no need to invoke other, more exotic causes for the wall radiation, for example, charge particle bombardment of the wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138067
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  • 7
    Electronic Resource
    Electronic Resource
    Tokamak Fusion Test Reactor horizontal high-resolution Bragg x-ray spectrometer (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1165-1168 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A bent quartz-crystal spectrometer of the Johann type with a spectral resolution of λ/Δλ= 10000–25000 is used on the Tokamak Fusion Test Reactor (TFTR) to determine central plasma parameters from the spectra of helium-like and lithium-like metal impurity ions (Ti, Cr, Fe, and Ni). The spectra are observed along a central radial chord and are recorded by a position-sensitive multiwire proportional counter with a spatial resolution of 250 μ. Standard delay-line time-difference readout is employed. The data are histogrammed and stored in 64 K of memory providing 128 time groups of 512-channel spectra. The central ion temperature and the toroidal plasma rotation are inferred from the Doppler broadening and Doppler shift of the Kα lines. The central electron temperature, the distribution of ionization states, and dielectronic recombination rates are obtained from satellite-to-resonance line ratios. The performance of the spectrometer is demonstrated by measurements of the Ti xxi Kα radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138023
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  • 8
    Electronic Resource
    Electronic Resource
    Measurements of the ion temperature and plasma rotation from Kα emission with the TFTR horizontal x-ray crystal spectrometer (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1853-1853 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The TFTR horizontal x-ray crystal spectrometer has been improved by installation of γ and neutron shielding and is now operating in the TFTR Test Cell up to the presently maximum neutron production rates of 2×1016 neutrons/s. Further optimization by using a modified detector may assure operation of the spectrometer during the DT phase when TFTR is covered by an igloo. The instrument is set up for simultaneous observation of the entire satellite spectrum of Ni xxvii, and it provides data on the time evolution of the central ion temperature and the central plasma rotation velocity. Ion temperatures of 20–30 keV have been measured under "supershot'' conditions. The highest rotation velocity observed with unidirectional injection was 1.1×106 m/s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140087
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  • 9
    Electronic Resource
    Electronic Resource
    Measurements of the ion temperature and plasma rotation from Kα emission with the TFTR horizontal x-ray crystal spectrometer (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2127-2130 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The TFTR horizontal x-ray crystal spectrometer has been improved by installation of γ and neutron shielding and is now operating in the TFTR Test Cell up to the presently maximum neutron production rates of 2×1016 neutrons/s. Further optimization by using a modified detector may assure operation of the spectrometer during the DT phase when TFTR is covered by an igloo. The instrument is set up for simultaneous observation of the entire satellite spectrum of Ni xxvii, and it provides data on the time evolution of the central ion temperature and the central plasma rotation velocity. Ion temperatures of 20–30 keV have been measured under "supershot'' conditions. The highest rotation velocity observed with unidirectional injection was 1.1×106 m/s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139974
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  • 10
    Electronic Resource
    Electronic Resource
    Measurements of radial profiles of the ion temperature and the plasma rotation velocity with the TFTR vertical x-ray crystal spectrometer (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2131-2134 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The TFTR vertical x-ray crystal spectrometer has now been operating with three crystals and position-sensitive detectors according to the original design specifications. The observed spectra of heliumlike Ti xxi, Cr xxiii, Fe xxv, and Ni xxvii have permitted a detailed comparison with the predictions from atomic theories, and they have provided data on the radial profiles of the ion temperature and toroidal rotation velocity, as well as the radial ion charge-state distribution in TFTR discharges. Central ion temperatures of 20 keV and central plasma rotation velocities of 5×105 m/s have been recorded from plasmas with auxiliary neutral beam heating. These experimental results are presented. Also discussed are further instrumental improvements, such as the installation of two additional crystals and detectors and the installation of γ and neutron shielding, which will make it possible to measure under full DD and DT operation with 27 MW of neutral beam injection where neutron production rates of 1019 neutrons/s are expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139975
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