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  • 1
    Electronic Resource
    Electronic Resource
    Visible spectroscopy surveys of the OHTE plasma (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 Jarrell-Ash 0.27-m triple grating spectrometer with a high-speed intensified diode array detector has been used to perform time-resolved surveys of the visible emission (2200-7000 A(ring)) from the OHTE plasma. Using a 512 diode array, spectra are obtained every 516 μs during the shot. The spectral width of the scan is 150, 300, or 1200 A(ring) depending on the grating selected. Surveys at up to 500 kA for OHTE plasmas indicate a complete absence of metal emission lines with the graphite bead vacuum liner. In the 5200-A(ring) region, a clear iindow has been identified for optical bremsstrahlung measurements. Other details of the spectra will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138079
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  • 2
    Electronic Resource
    Electronic Resource
    1-m normal incidence UV spectrometer for plasma measurements (abstract) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 870-870 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An Acton Research VM 521-SG UV monochromator has been equipped with an intensified diode array detector for use as a mid-UV spectrometer. 600 and 2400 gr/mm gratings are used in a turret assembly for either low-resolution surveys or high-resolution Doppler ion studies. The detector is a CsI coated MCP with a P-11 output phosphor. The 1024 diode array is scanned at a 1-MHZ video rate allowing a complete spectra to be obtained in 1.0 ms. System performance and preliminary operation on the OHTE plasma will be presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138080
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  • 3
    Electronic Resource
    Electronic Resource
    Recent progress toward high performance above the Greenwald density limit in impurity seeded discharges in limiter and divertor tokamaks : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2188-2198 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An overview is given of recent advances toward the realization of high density, high confinement plasmas with radiating mantles in limiter and divertor tokamaks worldwide. Radiatively improved mode discharges on the Torus Experiment for Technology Oriented Research 94 (TEXTOR-94) [Proceedings of the 16th IEEE Symposium on Fusion Engineering, 1995 (Institute for Electrical and Electronics Engineers, Piscataway, NJ, 1995), p. 470] have recently been obtained at trans-Greenwald densities (up to n¯/nGW=1.4) with high confinement mode free of edge localized modes (ELM-free H-mode) confinement quality. Experiments in DIII-D [J. Luxon et al., Proceedings of the 11th IAEA Conference on Plasma Physics and Controlled Nuclear Fusion Research (International Atomic Energy Association, Vienna, 1987), Vol. 1, p. 159] divertor plasmas with a low confinement mode edge have confirmed the dramatic changes in confinement observed with impurity seeding on TEXTOR-94. Recent experiment with impurity seeding on the Joint European Torus [Rebut et al., Fusion Eng. Des. 22, 7 (1993)], and the Japanese Atomic Energy Research Institute Tokamak 60 Upgrade [Horiike et al., Fusion Eng. Des. 16, 285 (1991); Hosogane et al., Proceedings of the 16th IAEA Conference on Plasma Physics and Controlled Nuclear Fusion Research Montreal, 1987 (International Atomic Energy Association, Vienna, 1987), Vol. 3, p. 555] have extended high confinement in ELMy H-mode plasmas to higher densities. Finally, recent progress in the physical understanding of radiating mantle plasmas is summarized. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1364513
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  • 4
    Electronic Resource
    Electronic Resource
    Impurity-induced turbulence suppression and reduced transport in the DIII-D tokamak : The 41st annual meeting of the division of plasma physics of the american physical society (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 1870-1877 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Long wavelength turbulence as well as heat and momentum transport are significantly reduced in the DIII-D tokamak [Plasma Physics and Controlled Nuclear Fusion Research (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] as a result of neon seeding of a low confinement mode negative central shear discharge. Correspondingly, the energy confinement time increases by up to 80%. Fully saturated turbulence measurements near ρ=0.7 (ρ=r/a) in the wave number range 0.1≤k⊥ρs≤0.6, obtained with beam emission spectroscopy, exhibit a significant reduction of fluctuation power after neon injection. Fluctuation measurements obtained with far infrared scattering also show a reduction of turbulence in the core, while the Langmuir probe array measures reduced particle flux in the edge and scrape-off layer. Gyrokinetic linear stability simulations of these plasmas are qualitatively consistent, showing a reduction in the growth rate of ion temperature gradient driven modes for 0〈k⊥ρs≤1.4, and nonlinear gyrokinetic simulations show a reduced saturated density fluctuation amplitude. The measured ωE×B shearing rate increased at ρ=0.7, suggesting that impurity-induced growth rate reduction is acting synergistically with ωE×B shear to decrease turbulence and reduce anomalous transport. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874010
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  • 5
    Electronic Resource
    Electronic Resource
    Modification of high mode pedestal instabilities in the DIII-D tokamak (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 1976-1983 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The amplitude and frequency of modes driven in the edge region of tokamak high mode (H-mode) discharges [type I edge-localized modes (ELMs)] are shown to depend on the discharge shape. The measured pressure gradient threshold for instability and its scaling with discharge shape are compared with predictions from ideal magnetohydrodynamic theory for low toroidal mode number (n) instabilities driven by pressure gradient and current density and good agreement is found. Reductions in mode amplitude are observed in discharge shapes with either high squareness or low triangularity where the stability threshold in the edge pressure gradient is predicted to be reduced and the most unstable mode is expected to have higher values of n. The importance of access to the ballooning mode second stability regime is demonstrated through the changes in the ELM character that occur when second regime access is not available. An edge stability model is presented that predicts that there is a threshold value of n for second regime access and that the most unstable mode has n near this threshold. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874053
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  • 6
    Electronic Resource
    Electronic Resource
    Very high- and high-confinement mode limited discharges in DIII-D (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1005-1011 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The first observations of marginally limited very high confinement mode (VH-mode) discharges have been achieved in DIII-D [Nucl. Fusion Special Supplement: World Survey of Activities in Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1990)] with significant reductions in peak heat flux conducted to plasma facing surfaces. In addition, quasistationary well limited high confinement-mode (H-mode) discharges have been obtained in DIII-D, also with reduced peak heat flux. This demonstration of reduced peak heat flux while maintaining high performance, i.e., high energy confinement time, can be important for the design of fusion ignition devices. Energy confinement enhancements in these high triangularity discharges are comparable to diverted discharges with similar parameters: τE/τITER-89P=2.9 for VH-mode and τE/τITER-89P=1.8 for quasistationary high confinement mode (H mode), where τITER-89P is the empirically derived low confinement mode (L-mode) energy confinement scaling relation [Nucl. Fusion 30, 1999 (1990)]. Comparisons of the conducted heat flux, particle flux, and radiated power profiles show a shift toward the inner wall as the discharge configuration becomes more limited. In addition to the advantage of reduced peak heat flux in these limiter discharges, such configurations also allow more effective use of the internal vessel volume, providing the potential for higher performance, i.e., higher plasma current at a fixed safety factor, q95. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871811
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  • 7
    Electronic Resource
    Electronic Resource
    Very high confinement discharges in DIII-D after boronization (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2181-2188 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A regime of very high confinement (VH mode) has recently been observed in DIII-D with global energy confinement times up to a factor of 3.5 above the ITER89-P L-mode scaling [Nucl. Fusion 30, 1999 (1990)] and 1.5 to 2 times greater than the DIII-D/JET edge-localized-mode-free H-mode scaling relation [Nucl. Fusion 31, 73 (1991)]. These discharges were obtained after boronization in DIII-D and are characterized by low radiated power and Zeff, increasing confinement time during the VH phase of the discharge and low Ohmic target density. The low radiated power and Zeff are a consequence of the boronization. During the VH phase these discharges exhibit an inward shift in the region of highest electric field shear and a large calculated edge bootstrap current. The outer region (ρ(approximately-greater-than)0.85) is calculated to be in the second stable regime to ideal ballooning modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860485
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  • 8
    Electronic Resource
    Electronic Resource
    Energy, particle and impurity transport in quiescent double barrier discharges in DIII-D : Review,Tutorial and Invited Papers from the 43rd Annual Meeting of the APS Division of Plasma Physics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1970-1980 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quiescent double barrier discharges (QDB) on DIII-D [Luxon et al., Fusion Technol. 8, Part 2A, 441 (1985)] exhibit near steady high performance (βNH∼7) with a quiescent H-mode edge, i.e., free of edge localized modes (ELMs), but with effective particle control and strongly peaked density profiles. These QDB discharges exhibit an internal transport barrier with low ion thermal transport despite incomplete turbulence suppression. Very short correlation lengths, which reduce the transport step size, however, characterize the residual turbulence. This observation is consistent with simulations using the GLF23 [Waltz et al., Phys. Plasmas 4, 2482 (1997)] model, which reproduce the core ion temperature profile even in the presence of finite turbulence. Increased retention of high-Z impurities is observed and core nickel concentrations (an intrinsic impurity in DIII-D) are as high as 0.3%. To quantify impurity transport, trace impurity injection has been performed in steady QDB discharges showing a fast influx followed by a slow pump out. The measured decay times of the core concentration of two nonrecycling impurities, F(Z=9) and Ca(Z=22), are 299 and 675 ms, respectively, while the energy confinement time is 111 ms. Time dependent analysis of neon influx yields both diffusivities and inward convection velocities significantly greater than neoclassical predictions in the same region of the plasma where measured ion thermal transport is near neoclassical predictions yet significant turbulence is observed. The boundary of these discharges is characterized by a saturated coherent magnetohydrodynamic mode, the edge harmonic oscillation, which takes the place of ELMs in facilitating particle control by allowing particle transport to the open field lines, where both wall- and cryopumping play a major role in particle exhaust. Hot (∼5 keV) ions observed in the outer scrape-off layer may enhance wall pumping. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1456064
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  • 9
    Electronic Resource
    Electronic Resource
    Three-filter colorimetry in DIII–D to measure in situ erosion and deposition of plasma facing surfaces (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 5257-5261 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Three-filter colorimetry has been introduced in the DIII–D tokamak to measure in situ the growth and the erosion of transparent wall coatings (a-C/B:H) in the divertor region. Colorimetry uses the interference of light on a transparent layer to measure the film thickness. The colorimetry setup at DIII–D consists of a light source, a black and white camera, and a filter wheel equipped with three broadband color filters. A white light source illuminates the area of interest. A picture with each filter is recorded and digitized. Thus the interference color of a semitransparent layer is measured and the film thickness is computed using the formalism of thin film optics. Since color cameras are more sensitive to neutron damage, a set of three filters was chosen which best matches the responsivity of a radiation-hardened B/W camera. In fact, one infrared filter and two visible filters are used. The three 2D camera images obtained from rotating the three filters into the line of sight of the camera are used to produce a 2D image of the change in film thickness due to the high flux of particles and power incident on the film during a diverted discharge. In a first measurement, the technique was used to measure the growth of a boron film in situ in the DIII–D tokamak. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146095
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  • 10
    Electronic Resource
    Electronic Resource
    A method to measure magnetic field perturbations in plasma devices (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 2883-2887 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Magnetic field perturbations with specific spatial geometry can be detected in the presence of a large magnetic field "background'' using printed circuit pickup coils which have the advantages of large effective area, near dc frequency response, precise geometry, thin profile, and low cost. The design and construction techniques to produce these coils are presented. A printed circuit coil has been used to detect the magnetic field from the perturbed plasma current distribution in the TEXT tokamak due to current in an external helical (m=7,n=3) winding. The measured sensitivity of this coil, ΔBcoil/Btotal, is ∼3×10−6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140622
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