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  • 1
    Electronic Resource
    Electronic Resource
    Ideal magnetohydrodynamic stability of the tokamak high-confinement-mode edge region : The 40th annual meeting of the division of plasma physics of the american physical society (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1925-1934 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ideal magnetohydrodynamic (MHD) stability of the tokamak edge is analyzed, with particular emphasis on radially localized instabilities; it is proposed that these are responsible for edge pressure gradient limits and edge localized modes (ELMS). Data and stability calculations from DIII-D [to appear in Proceedings of the 16th International Conference on Fusion Energy, Yokohama (International Atomic Energy Agency, Vienna, 1998), Paper No. IAEA-F1-CN-69/EX8/1] tokamak equilibria indicate that two types of instability are important: the ballooning mode (driven by pressure gradient) and the peeling mode (driven by current density). The characteristics of these instabilities, and their coupling, are described based on a circular cross-section, large aspect ratio model of the tokamak equilibrium. In addition, preliminary results are presented from an edge MHD stability code which is being developed to analyze general geometry tokamak equilibria; an interpretation of the density threshold to access the high-confinement-mode (H-mode), observed on COMPASS-D [Plasma Phys. Controlled Fusion 38, 1091 (1996)] is provided by these results. Experiments on DIII-D and the stability calculations indicate how to control ELMs by plasma shaping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873492
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  • 2
    Electronic Resource
    Electronic Resource
    Synergy of multiviewing spectroscopic diagnostics on COMPASS-D (invited) : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 881-887 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In the COMPASS-D tokamak three multiviewing diagnostic systems are combined by using the same collection optics. HeI line ratios from a helium thermal jet provide detailed edge Te(r) and ne(r) profiles. The spectrometer also provides the Dα profile. A Doppler spectrometer system provides Ti and Vθ profiles using HeII emission. The Te and ne profiles are used in extracting neutral densities from the Dα emissivities, and the radial electric field from the Doppler measurements. The behavior of Te(r), ne(r), 2nD(r), Er, and Vθ and their gradients can now be compared in detail to investigate the H-mode transition physics. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1323244
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  • 3
    Electronic Resource
    Electronic Resource
    A spatially scanning vacuum ultraviolet and visible range spectrometer for spectroscopy of tokamak plasmas in ASDEX-Upgrade (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 5433-5441 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A spatially scanning, combined vacuum-ultraviolet (VUV) and visible range spectrometer system for the spectroscopy of tokamak plasmas in the ASDEX-Upgrade experiment is described. This system is designed to allow flexible observation of about 2/3 of the boundary plasma using VUV (30–200 nm) and visible range spectrometers viewing along a common line of sight which can be scanned during the plasma discharge by means of a rotatable mirror. From successive spectra recorded using intensified, multichannel photodiode detectors and the recorded position data, spatial profiles of the plasma emission can be reconstructed. Because radiation losses from the boundary plasma can largely be attributed to line emission in the VUV spectral region, this instrument finds application in quantitative studies of radiation loss processes as well as to studies of impurity production and transport. Simultaneous observation in the visible spectral range facilitates an in situ absolute calibration of the VUV instrument by means of the "branching-ratios'' technique. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146065
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  • 4
    Electronic Resource
    Electronic Resource
    Optimized instrumentation for edge Te and ne measurements on COMPASS-D tokamak from He I line intensity ratios : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 355-358 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Instrumentation has been developed for the measurement of electron temperature and density profiles at the boundary of COMPASS-D tokamak plasmas from He I line intensities. The technique is applicable to measurements of ne and Te over the relevant ranges of 1017–1020 m−3 and 10–500 eV. Spectra from eight viewing chords viewing a thermal helium jet are recorded on a CCD sensor with (approximate)1 ms time resolution. A 0.6 m Czerny-Turner spectrometer, corrected for astigmatism using an internal, cylindrical lens optimizes throughput by availing of a 110×110 mm2, 300 l/mm grating. ne and Te profile measurements from L-mode (low) and quiescent H-mode (high) confinement plasmas are presented. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149504
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  • 5
    Electronic Resource
    Electronic Resource
    Time-resolved ion temperature measurements on the HBTX1A reversed field pinch (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1103-1104 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The energy distribution of the neutral particle emission (200 eV–2 keV) from the HBTX1A reversed field pinch has been observed, using a five-channel analyzer, at 20-μs intervals throughout the duration of the discharge. The relative number of high-energy neutrals emitted increases with currents up to 250 kA above which there is little change. Preliminary analyses show that the ion temperature of the bulk of the plasma is in the range 70–120 eV, rather than the few electron volts expected from electron–ion collisions. Equally, the rapid evolution to this temperature (〈0.5 ms) is not accountable by equipartition (τeq∼3 ms). Long thermalization times (∼1 ms), compared with short time-scale excursions (∼100 μs) in the high-energy neutrals indicate that there are nonthermal ions at ∼10 times the Maxwellian temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138237
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  • 6
    Electronic Resource
    Electronic Resource
    Spectroscopy of plasmas with a multifiber commutator (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2015-2016 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Spatially resolved spectra have been obtained, during a single discharge, with one spectrometer using an optical multifiber commutator (OMC). We report results from this device which can be preprogrammed to select up to nine viewing chords, via high transmission optical fibers. This arrangement has been incorporated with a multichannel (OMA) spectrometer, where the fiber-to-fiber switching time matches the basic video scan of the detector (16 ms). The spectrometer can be operated in medium resolution mode (0.3 A(ring)) with a conventional grating or with high resolution (0.05 A(ring)) by substituting an echelle grating. The apparatus has been used for the evaluation of ion temperatures in the source and extraction regions of the Culham negative ion source. It is presently employed in JET for the study of the relative impurity influxes from the wall, the limiters, and the rf antennas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138775
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  • 7
    Electronic Resource
    Electronic Resource
    Profile evolution of edge parameters during L/H and H/L mode transitions on COMPASS-D (2000)
    Springer
    Czechoslovak journal of physics 50 (2000), S. 1451-1461 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract On COMPASS-D the profile evolution of electron density, electron temperature, perpendicular electric field, poloidal impurity velocity, and neutral density at the outboard mid-plane has been investigated during ohmic single null diverted (SND) discharges undergoing an L/H, H/L, and another L/H transition. This was achieved using a novel combined diagnostic consisting of thermal helium beam and Doppler spectrometry, sharing the same lines of sight. To generate the transitions first an ELM-free H-mode phase was produced by terminating the gas fuelling. Within this H-mode a stepped gas puff was applied triggering an intermediate L-mode phase followed by a second ELM-free phase. It was found that on COMPASS-D the L/H transition is not preceded by a change in velocity or electric field shear. The maximum electric field shear of ∇Eψ ≈ 2 × 103 kV/m2 develops after the L/H transition around the 95% flux surface. Although the neutral density at the separatrix is of the order n D ≈ 1017m−3 no indication of a local influence could be concluded. However, a correlation between the decay of the shear and the gas puff was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022807931846
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  • 8
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    Strategic Development in Sinkiang (1961)
    New York : Periodicals Archive Online (PAO)
    Foreign Affairs. 39:2 (1961:Jan.) 312 
    Details
    ISSN: 0015-7120
    Topics: Political Science , Law
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:1086-1961-039-02-000014
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