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  • 1
    Electronic Resource
    Electronic Resource
    Poloidal rotation in Alcator C (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2020-2022 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The poloidal rotation velocity in the edge region of ohmically heated Alcator C plasmas was measured using the Doppler shift of impurity emission lines. The measurements were made using a high-resolution, photon counting detector, sensitive to wavelengths from ∼1200 to ∼2000 A(ring), mounted in the exit plane of a 1-m Ebert–Fastie spectrometer. The transitions used were the 2s2p 1P01–2p2 1D2 at 1371.292 A(ring) in O v and 2s 2S1/2–2p 2P01/2 at 1242.804 A(ring) in N v, both of which exist near the limiter radius in Alcator C. The measured rotation velocity is ∼4.1×105 ±2.1×105 cm/s at n¯e∼1.7×1014 cm−3 in the direction of the electron diamagnetic drift and is ∼1.4×105 ±2.5×105 cm/s at n¯e∼2.3×1014 cm−3 in the ion diamagnetic drift direction, although the error bars associated with this last measurement do not preclude the possibility of zero rotation or rotation in the electron diamagnetic drift direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138777
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic-field measurement based on Zeeman effect in lines excited by charge exchange recombination (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2029-2031 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: It is suggested that the poloidal magnetic field in a tokamak may be deduced from the analysis of circular polarization of light impurity ion lines excited by charge-exchange recombination. Visible or near-ultraviolet transitions in hydrogenlike oxygen and carbon are considered. Estimations of the linewidths and the magnitude of the Zeeman effect show that, with appropriate polarization analyzer and the experiment geometry, the poloidal component of the magnetic field can, in principle, be measured. Uncertainties of the model used to calculate the polarized line profiles do not affect the interpretation of the measurement in a fundamental way and may be accounted for experimentally by calibrating the polarization effect against the components of the toroidal field. In principle, the analysis of only one transition may provide information about the whole poloidal field profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138780
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  • 3
    Electronic Resource
    Electronic Resource
    Time-resolving multispatial grazing incidence spectrograph for plasma fusion diagnostics (abstract) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 869-869 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A grazing incidence spectrograph which operates in the EUV (40 to 350 A(ring)) that has multispectral, temporal, and spatial resolving capabilities is being constructed for plasma fusion diagnostics. The spectrograph achieves a simultaneous spectral coverage of 20 and 60 A(ring) when centered on 40 and 350 A(ring), respectively, with ∼1-A(ring) resolution. The detector consists of an image intensifier fiber optically coupled to 3 area array detectors (CCDS), which can be read out in 5 ms, thereby determining the time resolution of the instrument. The spatial resolution is accomplished by using the astigmatism inherent to a concave grating in grazing incidence, coupled with the pinhole camera effect produced by an entrance slit of limited height. The spectrograph can view ∼54 cm of plasma which is 2 m away from the entrance slit with 4- and 8-cm resolution at 350 and 40 A(ring), respectively. We will present the results of a feasibility study, the spectrograph design, and the results of the data reduction and interpretation codes which are under development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138078
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  • 4
    Electronic Resource
    Electronic Resource
    Spectroscopic measurement of the poloidal field profile in the TEXT (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1632-1634 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The poloidal field profile in the Texas Experimental Tokamak is determined from the analysis of circular polarization of the forbidden (magnetic dipole) line Ti xvii 3834 A(ring). A high-sensitivity polarimeter measures the difference between right- and left-hand circularly polarized line profiles, a quantity which is directly proportional to the magnitude of the magnetic field component in the direction of observation. The fractional circular polarization smaller than 10−2 can be detected, which allows determining the poloidal magnetic field in the center of the plasma with uncertainty as small as 50 G. The instrumentation is relatively simple and inexpensive. Description of the polarimeter and results of measurement of the poloidal field profile and the safety factor on the tokamak axis are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140168
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  • 5
    Electronic Resource
    Electronic Resource
    High spectral resolution, photon counting detector for Doppler temperature measurements in magnetically confined plasmas (1987)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 520-529 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes the design, construction, and performance of a single-stage microchannel-plate image intensifier used as a photon counting detector over the wavelength range from 1150 to ∼2000 A(ring). The intensifer incorporates three high strip current (∼300 μA) microchannel plates, constructed with 12-μ-diam channels and 15-μ center–center spacing, in a "Z'' configuration. The use of high strip current MCPs requires gating the power supply to protect the plates from thermal runaway of the strip current. The output pulses are proximity focused onto a P-46 phosphor screen, which is fiber-optically coupled to a linear, self-scanning photodiode array. Maximum frame rates for the photodiode array are ∼ 125 000 frames/s, with maximum count rates of ∼25 000 photoevents/s. The detector was placed at the focal plane of a 1-m focal length Ebert–Fastie spectrometer and the performance characteristics of the spectrometer-detector system were evaluated using a hollow cathode Pt lamp. The linewidths measured during this evaluation demonstrate that the spatial resolution of the detector is better than 50 μ. The spectrometer-detector system was then used to determine ion temperatures from Doppler broadened impurity lines emitted from plasmas of the Alcator C tokamak. This detector demonstrated more than an order of magnitude increase in sensitivity compared to a photon-counting photomultiplier tube with a vibrating mirror previously used for these measurements with the same spectrometer. This permitted a determination of the central ion temperature of the Alcator C tokamak using the "forbidden'' line of Fe xii at 1354.1 A(ring) which was not detected with the previous system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139263
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  • 6
    Electronic Resource
    Electronic Resource
    Deficiency of molecular hydrogen in the disk of β Pictoris (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 412 (2001), S. 706-708 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Molecular hydrogen (H2) is by far the most abundant material from which stars, protoplanetary disks and giant planets form, but it is difficult to detect directly. Infrared emission lines from H2 have recently been reported towards β Pictoris, a star harbouring a young ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35089006
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  • 7
    Electronic Resource
    Electronic Resource
    An extreme ultraviolet spectroscopic diagnostic for fluctuations of electron density and temperature in tokamak plasmas (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5511-5518 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extreme ultraviolet (XUV) spectral line emissivities, originating from resonant transitions with upper states excited mainly from ground or both ground and lowest metastable states by electron collisional excitations of highly ionized intrinsic impurities in tokamak plasmas, are linear functions of both electron density and temperature fluctuations, ñe and T˜e, when the fluctuations are small and at high frequency. Correlations between measured intensities of spectral lines can thus provide localized measurements of the fluctuations. Newly developed XUV monochromators of high throughput enable accurate and fast diagnostics of ñe and T˜e for the study of the tokamak plasma microturbulence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347010
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  • 8
    Electronic Resource
    Electronic Resource
    Scanning polarimeter for measurement of the poloidal magnetic field in a tokamak (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2341-2350 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The internal magnetic field in a magnetically confined plasma may be deduced from the analysis of circular polarization of spectral lines emitted by the plasma. The theory of the measurement and a detailed design of a polarimeter constructed to measure the poloidal field profile in the Texas Experimental Tokamak (TEXT) are presented. The instrument measures the difference between left-hand and right-hand circularly polarized line profiles, a quantity directly proportional to the magnetic field component in the direction of observation. The high throughput of the Fabry–Perot interferometer employed in this design, combined with efficient light-collecting optics and lock-in detection of the polarization signal, allows measurement of the fractional circular polarization of the magnetic dipole line Ti xvii 3834 A(ring) with an accuracy on the order of 10−3. The line-of-sight averaged poloidal field is determined with uncertainty as small as 50 G. The line emission used in the present measurement is not well localized in the plasma, necessitating the use of a spatial inversion procedure to obtain the local values of the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139959
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  • 9
    Electronic Resource
    Electronic Resource
    Safety factor on the axis of a tokamak during Ohmically heated sawtoothing discharges from a localized measurement of circular polarization of the Lii 6708 A(ring) line (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 809-814 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Analysis of the circular polarization of the Lii 6708 A(ring) line emitted from a monoenergetic lithium beam provides a spatially resolved measurement of the poloidal magnetic field on the Texas experimental tokamak [Nucl. Technol. Fusion 1, 479 (1989)]. Determined from the measured magnetic field, the safety factor on the magnetic axis during Ohmically heated sawtoothing discharges is near unity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859317
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  • 10
    Electronic Resource
    Electronic Resource
    Space- and time-resolving spectrograph for high-temperature plasma diagnostics (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2041-2042 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Construction of an EUV (60 –370 A(ring)) space- and time-resolving, grazing incidence spectrograph (STRS) is described. The simultaneous spectral coverage of the instrument ranges from 40 to 75 A(ring), depending on the wavelength region. The spectral resolution is about 1 A(ring). The spatial resolution, accomplished by using the pinhole camera effect and the inherent astigmatism of a concave grating in grazing incidence, is about 2 cm, with a total field of view of 60 cm at a distance of 2 m from the plasma. The detector consists of a 75-mm MCP image intensifier optically coupled to three CCD area array detectors. Time resolution of up to 2 ms is achieved with high-speed readout electronics. A PDP 11/73 minicomputer controls the spectrograph and collects and reduces 3.0 Mbyte of data per shot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138783
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