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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1156-1159 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Thermal imaging cameras sensitive to 3–5 μ radiation are routinely used to measure heat flow to the main limiter, to the vacuum vessel wall behind the main limiter, and to the divertor plate limiters. The cameras are equipped to provide either a standard television image, one frame per ∼16.7 ms, or a surface temperature profile on one line of the image with a time resolution of ∼125 μs. In the former mode, we can determine both the location and the intensity of the heating on the main limiter during multimegawatt neutral-beam injection into plasma; in the latter mode, we can measure heat pulses striking the limiter from plasma processes occurring on fast timescales (e.g., Dα spikes of ∼500 μs duration). Data is stored in both video image and digitized forms. In the latter, a "peak-sample-hold'' circuit electronically records the maximum signal of each line sweep and stores this data in digitized form on magnetic tape. This facilitates later comparisons of infrared camera data with other diagnostic signals using plotting packages on the DEC-10.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 938-938 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Thermal imaging cameras sensitive to 3–5 μ radiation are routinely used to measure heat flow to the main limiter, to the vacuum vessel wall behind the main limiter, and to the divertor plate limiters. The cameras are equipped to provide either a standard television image with a time resolution of ∼16.7 ms or a surface temperature profile on one line of the image with a time resolution of ∼125 μs. In the former mode, we can determine both the location and the intensity of the heating on the main limiter during multi-megawatt neutral-beam injection into plasma; in the latter mode, we can measure heat pulses striking the limiter from plasma processes occurring on fast time scales (e.g., Hα spikes of ∼500-μs duration). Data is stored in both video image and digitized forms. In the latter, a "peak-sample-hold'' circuit electronically records the maximum signal of each line sweep and stores this data in digitized form on magnetic tape. This facilitates later comparisons of infrared camera data with other diagnostic signals using plotting packages on the DEC-10.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ELMing (edge-localized) H-mode discharges with densities as high as 40% above the Greenwald density and good energy confinement, HITER-89P=2, were obtained with D2 gas puffing on DIII-D [Chan et al., Proceedings of the 16th IAEA Conference, Montreal (International Atomic Energy Agency, Vienna, 1996), Vol. 1, p. 95]. These discharges have performance comparable to the best pellet fueled DIII-D discharges. Spontaneous peaking of the density profile was an important factor in obtaining high energy confinement. Without density profile peaking, the energy confinement at high density degraded with reduction in the H-mode pedestal pressure under the stiff temperature profile conditions observed at high density on DIII-D. Reduction in the pedestal pressure was associated with loss of access to the second stable regime for ideal ballooning modes at the edge, and change in the edge-localized mode (ELM) instability from a low to high toroidal mode number. Gyrokinetic stability calculations indicate that the core of the high-density discharges is dominated by ion temperature gradient mode turbulence. A turbulent transport simulation with the GLF23 [Waltz et al., Phys. Plasmas 4, 2482 (1997)] code produced stiff temperature profiles in agreement with the experiment and did not indicate the formation of an internal transport barrier. Helium transport studies showed an anomalous inward particle pinch at high density. The highest density discharges were terminated by onset of a magnetohydromagnetic instability, which is consistent with destabilization of neoclassical tearing modes through peaking of the pressure profile. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1878-1880 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The power flow to the DIII-D divertor targets is routinely measured using infrared (IR) thermography. An IR television camera sensitive to radiation in the 8–12-μm range views the divertor region using a set of germanium optics. Digital signal processing is used to extract the desired surface temperature profiles from the analog data ((approximately-equal-to)12 Mbytes) stored on videotape. Inversion of these data using a simple matrix formulation of the inverse heat conduction problem then yields the incident heat flux as a function of space and time. Results from a DIII-D discharge are included.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The radiation of divertor heat flux on DIII-D [J. Luxon et al., in Proceedings of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1987), p. 159] is shown to greatly exceed the limits imposed by assumptions of energy transport dominated by electron thermal conduction parallel to the magnetic field. Approximately 90% of the power flowing into the divertor is dissipated through low-Z radiation and plasma recombination. The dissipation is made possible by an extended region of low electron temperature in the divertor. A one-dimensional analysis of the parallel heat flux finds that the electron temperature profile is incompatible with conduction-dominated parallel transport. Plasma flow at up to the ion acoustic speed, produced by upstream ionization, can account for the parallel heat flux. Modeling with the two-dimensional fluid code UEDGE [T. Rognlien, J. L. Milovich, M. E. Rensink, and G. D. Porter, J. Nucl. Mater. 196–198, 347 (1992)] has reproduced many of the observed experimental features. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of experiments was conducted on the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)] to investigate the physical processes which limit density in high confinement mode (H-mode) discharges. The typical H-mode to low confinement mode (L-mode) transition limit at high density near the empirical Greenwald density limit [M. Greenwald et al., Nucl. Fusion 28, 2199 (1988)] was avoided by divertor pumping, which reduced divertor neutral pressure and prevented formation of a high density, intense radiation zone (MARFE) near the X-point. It was determined that the density decay time after pellet injection was independent of density relative to the Greenwald limit and increased nonlinearly with the plasma current. Magnetohydrodynamic (MHD) activity in pellet-fueled plasmas was observed at all power levels, and often caused unacceptable confinement degradation, except when the neutral beam injected (NBI) power was ≤3 MW. Formation of MARFEs on closed field lines was avoided with low safety factor (q) operation but was observed at high q, qualitatively consistent with theory. By using pellet fueling and optimizing discharge parameters to avoid each of these limits, an operational space was accessed in which density ∼1.5×Greenwald limit was achieved for 600 ms, and good H-mode confinement was maintained for 300 ms of the density flat-top. More significantly, the density was successfully increased to the limit where a central radiative collapse was observed, the most fundamental density limit in tokamaks. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent measurements of the two-dimensional (2-D) spatial profiles of divertor plasma density, temperature, and emissivity in the DIII-D tokamak [J. Luxon et al., in Proceedings of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1987), p. 159] under highly radiating conditions are presented. Data are obtained using a divertor Thomson scattering system and other diagnostics optimized for measuring the high electron densities and low temperatures in these detached divertor plasmas (ne≤1021 m−3, 0.5 eV≤Te). D2 gas injection in the divertor increases the plasma radiation and lowers Te to less than 2 eV in most of the divertor volume. Modeling shows that this temperature is low enough to allow ion–neutral collisions, charge exchange, and volume recombination to play significant roles in reducing the plasma pressure along the magnetic separatrix by a factor of 3–5, consistent with the measurements. Absolutely calibrated vacuum ultraviolet spectroscopy and 2-D images of impurity emission show that carbon radiation near the X-point, and deuterium radiation near the target plates contribute to the reduction in Te. Uniformity of radiated power (Prad) (within a factor of 2) along the outer divertor leg, with peak heat flux on the divertor target reduced fourfold, was obtained. A comparison with 2-D fluid simulations shows good agreement when physical sputtering and an ad hoc chemical sputtering source (0.5%) from the private flux region surface are used. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2988-2988 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Six infrared cameras measure temperature changes on the protective graphite armor inside the DIII-D vacuum vessel. Simultaneous time-dependent temperature measurements are made on armor tiles located on the centerpost and divertor regions, and on both outboard limiters. The nearly complete poloidal coverage is useful in measuring both the plasma heat flux distributions inside the vessel and the plasma power balance. Spatial resolution of each camera system is (approximately-less-than)1 cm, while the minimum resolvable time is 125 μs. Data from the IR TV systems are recorded on video tape, and are post-processed serially, using an image processor with an AT-compatible microcomputer. The processing system controls all VCRs, interprets DIII-D timing pulses, digitizes video data in the predetermined regions of interest, averages digitized signals to reduce noise, and constructs data files which are then stored as part of the permanent shot record.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3557-3561 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Six infrared cameras measure temperature changes on the protective graphite armor inside the DIII-D vacuum vessel. Simultaneous time-dependent temperature measurements are made on armor tiles located on the centerpost and divertor regions, and on both outboard limiters. The nearly complete poloidal coverage is useful in measuring both the plasma heat flux distributions inside the vessel and the plasma power balance. Spatial resolution of each camera system is (approximately-less-than)1 cm, while the minimum resolvable time is 125 μs. Data from the IR TV systems are recorded on video tape, and are post-processed serially, using an image processor with an AT-compatible microcomputer. The processing system controls all VCRs, interprets DIII-D timing pulses, digitizes video data in the predetermined regions of interest, averages digitized signals to reduce noise, and constructs data files which are then stored as part of the permanent shot record.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 5 (1972), S. 85-100 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es werden Versuchsergebnisse mitgeteilt, die mit einer früher entwickelten Methode zur Messung der örtlichen Wärmeübertragung an blanke und keramikumhüllte Metalldrähte von einem thermisch hochionisierten Plasma gewonnen wurden. Diese Ergebnisse werden mit der Theorie verglichen. Ein frei brennender Bogen in Argon bei Atmosphärendruck ergibt ein Plasma im lokalen thermodynamischen Gleichgewicht. In Ebenen parallel zur Anode werden Drahtsonden durch das Plasma geschwenkt. Die Drähte entziehen dem Plasma keinen Nettostrom. Durch Versuch wird festgestellt, daß die Schicht zwischen ungestörtem Plasma und Sondenoberfläche nicht im chemischen Gleichgewicht ist. Die Werte zeigen, daß hierbei die Wärmeübertragung zum Draht bestimmt wird durch den Energietransport der Teilströme von Elektronen und Ionen zur Sondenoberfläche, wie er sich aus dem Potential der Sonde in Bezug auf das Plasma ergibt. Diese Versuchstechnik liefert ein experimentell bestätigtes Modell für den Wärmeübergang an in Plasma eingetauchte Drähte in einem weiten Bereich der Plasma-Zustandsgrößen, einschließlich einer Variation des Ionisationsgrades von hundert Prozent.
    Notes: Abstract Results obtained with a previously developed technique for measuring local heat transfer to bare and ceramic coated metal wires from a dense, highly thermallyionized plasma are presented and compared with theoretical predictions. A free-burning arc in argon at atmospheric pressure provides a plasma in local thermodynamic equilibrium. Wire probes are swept through this plasma in planes parallel to the anode. The wires do not draw a net current from the plasma. Experimental evidence indicates that the layer between the undisturbed plasma and the probe surface is not in chemical equilibrium. The data show that heat transfer to the wire in this situation is dominated by the energy transport associated with electron and ion partial currents to the probe surface as determined by the potential of the probe with respect to the plasma. The data obtained using this technique provide an experimentally verified model for the heat transfer to wires immersed in a plasma over a wide range of plasma conditions including a 100 percent variation in the degree of ionization.
    Type of Medium: Electronic Resource
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