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  • 1
    Electronic Resource
    Electronic Resource
    Bragg rotor spectrometer for tokamak diagnostics (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2159-2161 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high-throughput broadband (1–24-A(ring)) x-ray spectrometer has been demonstrated on the divertor injection tokamak experiment (DITE) tokamak. A hexagonal rotor supporting six diffractors may be driven in several modes, ranging from a full spectral survey at ∼10 Hz to a stationary, monochromator mode. Wavelength resolution, 500(approximately-less-than)λ/Δλ(approximately-less-than)1000, is governed by gridded or slotted collimators. A multiwire gas proportional counter provides a measure of energy discrimination, which together with the large instrument aperture, gives sufficient sensitivity and signal/noise ratio to allow measurement of the continuum radiation from the tokamak. The instrument has a self-contained vacuum system which allows full spatial scans of the DITE plasma. Data acquisition and drive mechanisms for the rotor and filter selection, are controlled remotely from a computer. Results are presented of fast spectral surveys and time evolution of impurity emission during impurity injection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138716
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  • 2
    Electronic Resource
    Electronic Resource
    Axial observation of a beam-foil source
    Amsterdam : Elsevier
    Physics Letters A 126 (1988), S. 253-257 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(88)90756-6
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Quantitative spectroscopy of x-ray lines and continua in tokamaks (abstract) : 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. 1063-1063 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Crystal and synthetic multilayer diffractors, deployed either as flat Bragg reflectors, or curved, as in the Johann configuration, have been used to study the spectrum of COMPASS-D and other tokamaks in the wavelength region 1–100 Å. In particular, line emission from CIXVI and other He-like ions of the third atomic period elements have been shown to be a rich source of diagnostic information on ion transport and impurity ion accumulation, ion and electron temperatures, and plasma fluid velocities. In this article, we concentrate on the measurement of absolute photon fluxes and the derivation of volume emissivities of the lines and continua in the x-ray region. The sensitivities of these instruments to absolute photon flux are constructed from the individual component efficiencies, including published values of the diffractor reflectivities. Where diffractors have been used for which there is no published information, the reflectivity is measured using a double-axis goniometer or from line branching ratios. Changes in the effective ion charge state, Zeff, have been derived for different operating conditions, from the absolute intensity of the continuum at ∼4 Å in COMPASS-D. From the irradiances of the line emission, changes in the absolute level of impurities following "boronization" of the vacuum vessel have been documented.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147916
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  • 4
    Electronic Resource
    Electronic Resource
    General purpose high-resolution x-ray crystal spectrometer (abstract) : 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. 5022-5022 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This spectrometer was designed to give access to a wide range of Bragg angles and crystal focal lengths while using the Rowland circle radius as a free parameter. Stability is achieved using a rigid beam or "Rowland chord,'' which provides a reference axis for all the critical alignments, the chord length being variable between about 0.2 and 5 m. Crystals of size up to 100×30×0.5 mm can be accommodated in a novel four-pillar jig, (λ/δλ) is typically 104 in the wavelength range from 0.1 to 1.3 nm, depending on the crystal. Various detectors have been used, including photographic film, multiwire gas proportional counters and large area CCD detectors, the latter having a 2-D spatial resolution of 22.5 μm (1152×1242 pixels, 26×28 mm2), a quantum efficiency greater than 20% between 0.7 and 12 keV and an energy resolution of about 150 eV. By sacrificing energy resolution, a one-dimensional mode with on-chip binning allows ∼ms time resolution of spectra from high flux sources such as tokamaks and synchrotrons. Results presented include photographic spectra from tokamak, beam foil and laser produced sources, and CCD spectra from tokamak and standard electron-beam excitation laboratory sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143478
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  • 5
    Electronic Resource
    Electronic Resource
    Bragg spectroscopy of impurities during the JET preliminary tritium experiment : 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. 5023-5025 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Two Bragg spectrometers shared a shielded beamline, and monitored all significant plasma impurities throughout the Joint European Torus (JET) preliminary tritium experiment. The JET Active Phase Double Crystal Monochromator and a Bragg rotor spectrometer together monitored K-shell lines of Be, C, O, and Cl, and L-shell lines from metals such as Ni and Zn, in the wavelength range 0.2–11 nm. Background radiation was recorded during and after discharges, to assess the signal-to-noise ratio, and to monitor any activation or tritium ingress. Bragg spectroscopy was shown to be suitable for all impurities in magnetically confined D–T plasmas, using a thin foil to isolate tritium, and a low f-number shielded beamline. Future improvements to the signal-to-noise ratio are discussed in the context of a next-step machine such as ITER.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143480
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  • 6
    Electronic Resource
    Electronic Resource
    Double-crystal x-ray spectroscopy at JET (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 889-898 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A double-crystal monochromator has been brought into operation at JET to measure absolute wavelengths and intensities of impurity spectral lines in the soft x-ray region from about 0.1 to 2.3 nm. It is capable of operating also during the deuterium-tritium (active) phase of JET because its detector is very effectively shielded against neutrons and hard x rays. The spectrometer has been swept over a wide wavelength range, around characteristic line groups as well as monochromatic line scans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142026
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  • 7
    Electronic Resource
    Electronic Resource
    Two-axis goniometer for reflectivity measurements of x-ray diffractors used in fusion research (abstract)a) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 529-529 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Quantitative measurements of the line and continua emissivities and the analyses of spectral line profiles are essential steps in the interpretation of the x-ray emission from high-temperature fusion plasmas. One method of placing the emissivities on an absolute basis is to use an absolutely calibrated spectrometer to record the data. The overall sensitivity of the spectrometer can be constructed in terms of the efficiencies of its separate components, the most intractable being Rc, the reflection integral of the diffractor. To this end, a new, compact, two-axis diffractometer, incorporating modern robotic technology, such as direct-drive servomotors with closed-loop operation from built-in arcsec optical encoders, has been constructed. Improved features of this double-axis goniometer include the use of fixed line-of-sight x-ray sources with the capability of operation in the (1,−1) parallel, nondispersive mode or the antiparallel, (1,+1), dispersive mode. The diffractometer is now being used to calibrate x-ray diffractors, filters, mirrors, and detectors associated with x-ray spectroscopy of fusion plasmas. At certain wavelengths, where line branching ratios involving visible transitions are available, the fusion plasma may itself be used as a transfer standard of x-ray luminosity, allowing an independent check on the diffractometer values of Rc. Applications to the analyses of impurity concentrations in tokamaks are described while future applications of the diffractometer to radiation damage studies of x-ray and optical components [Hill et al., Rev. Sci. Instrum. 63, 5032 (1992)] used in D-T burning plasma experiments are envisaged. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146339
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  • 8
    Electronic Resource
    Electronic Resource
    Quantitative spectroscopy of x-ray lines and continua in Tokamaks (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1734-1738 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Crystal and synthetic multilayer diffractors, deployed either as flat Bragg reflectors, or curved, as in the Johann configuration, are used to study the spectrum of COMPASS-D and other tokamaks in the wavelength region of 1–100 Å. In this article, we concentrate on the measurement of absolute photon fluxes and the derivation of volume emissivities of the lines and continua in the x-ray region. The sensitivities of these instruments to absolute photon flux have been constructed ab initio from the individual component efficiencies, including published values of the diffractor reflectivities, which have been checked or supplemented by measurements using a double-axis goniometer or from line branching ratios. For those tokamak plasmas, where the elemental abundances and effective ion charge are documented, the x-ray continuum intensity itself has been used as a calibration source to derive absolute instrument sensitivity, in reasonable agreement with the ab initio method. In the COMPASS-D Tokamak, changes in the effective ion charge state, Zeff, have been derived for different operating conditions, from the absolute intensity of the continuum at ∼4 Å. From the radiances of the line emission, changes in the absolute level of impurities following "boronization" of the vacuum vessel have also been documented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147983
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  • 9
    Electronic Resource
    Electronic Resource
    Bragg rotor spectrometer for the JET tokamak (abstract) : 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. 5022-5022 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Bragg rotor spectrometer uses diffractors ranging from LiF (420) (2d=0.18 nm) to a multilayer mirror (Ni–C 2d=11.7 nm). The extension to longer wavelengths is particularly useful at JET, where radiated power and Zeff are usually dominated by light impurities such as Be and C, whose H- and He-like transitions lie between about 2.5 and 10 nm. A hexagonal rotor scans six diffractors sequentially and gives either full coverage of the soft x-ray spectrum (to monitor a range of ionization stages of any possible impurity), or high monochromatic sensitivity (to monitor trace impurities and give time resolution of ∼10 μs for the study of transient events such as impurity injection). A large area gas proportional counter covers a Bragg angle range from 20° to 70°, with each of its ten anodes being connected to an independent amplifier-discriminator chain, allowing count rates up to 20 MHz to be processed. Moderate resolving power is provided by a 1:600 Soller collimator. A smaller rotor is mounted with a side-by-side array of four small diffractors, and is reciprocated over a relatively small Bragg angle range to give a time resolution of 20 ms for about ten representative lines (for routine analysis of radiated power components).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143479
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  • 10
    Electronic Resource
    Electronic Resource
    Two-axis goniometer for reflectivity measurements of x-ray diffractors used in fusion researcha) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1175-1179 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Quantitative measurements of the line and continua emissivities and the analyses of spectral line profiles are essential steps in the interpretation of the x-ray emission from high-temperature fusion plasmas. One method of placing the emissivities on an absolute basis is to use an absolutely calibrated spectrometer to record the data. The overall sensitivity of the spectrometer can be constructed in terms of the efficiencies of its separate components, the most intractable being Rc, the reflection integral of the diffractor. To this end, a new, compact, two-axis diffractometer, incorporating modern robotic technology, such as direct-drive servomotors with closed-loop operation from built-in arcsec optical encoders, has been constructed. Improved features of this double-axis goniometer include the use of fixed line-of-sight x-ray sources with the capability of operation in the (1,−1) parallel, nondispersive mode or the antiparallel, (1,+1), dispersive mode. The diffractometer is now being used to calibrate x-ray diffractors, filters, mirrors, and detectors associated with x-ray spectroscopy of fusion plasmas. At certain wavelengths, where line branching ratios involving visible transitions are available, the fusion plasma may itself be used as a transfer standard of x-ray luminosity, allowing an independent check on the diffractometer values of Rc. Applications to the analyses of impurity concentrations in tokamaks are described while future applications of the diffractometer to radiation damage studies of x-ray and optical components [Hill et al., Rev. Sci. Instrum. 63, 5032 (1992)] used in D-T burning plasma experiments are envisaged. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146001
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    Paper (German National Licenses)
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