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  • 1
    Electronic Resource
    Electronic Resource
    An active spectrometer (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1258-1263 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes a new type of correlation spectrometer, dubbed an "active spectrometer." It utilizes an oscillating mirror in a 1/4-m-Rowland circle spectrometer configuration to displace the spectrum periodically in the dispersion direction relative to fixed exit slits. The wavelength of the light passing through each slit is modulated sinusoidally at the mechanical oscillation frequency and its intensity is measured with a spot detector such as a photomultiplier or photodiode. With a PC-based control/data acquisition system, the signal from each detector is sampled digitally at a frequency constrained to be an integral multiple of the mirror drive frequency. From the resultant phase locking between the signal sampling and the mirror oscillation, it follows that the correlation function between the signal and mirror phase angle is obtained simply by averaging the data from successive mirror scans. Such a scan-averaged spectrum with low noise may then be compared with digitally stored reference spectra obtained through the same instrument. ac coupling of detector and amplifier results in rejection of continuum light and, when photodiodes are used as detectors, the maximization of preamplifier gain. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149582
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Fluid Mechanics of Waste-Water Disposal in the Ocean (1975)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 7 (1975), S. 187-211 
    Details
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.fl.07.010175.001155
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  • 4
    Electronic Resource
    Electronic Resource
    Radiative divertor plasmas with convection in DIII-D : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1736-1743 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.872842
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  • 5
    Electronic Resource
    Electronic Resource
    The two-dimensional structure of radiative divertor plasmas in the DIII-D tokamak : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1761-1773 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.872278
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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    High-resolution spectroscopy of the D iii–D divertor region : 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. 603-605 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The results of spectral measurements in the D iii–D divertor region, carried out using a high-resolution spectrometer and a survey spectrograph developed at the TRINITI Laboratory, Russia are presented in this report. Observations were made along a vertical chord passing through the X point and intersecting the divertor floor at the major radius of the V1 ports. The high-resolution spectrometer is designed for simultaneous measurements along eight spatial chords with a time resolution of 7 ms. Each of the eight spectra is dispersed over 512 pixels on an intensified charge coupled device (CCD) detector. 768 frames of data are recorded directly to RAM memory of a PC computer during every discharge. High optical throughput is achieved simultaneously with high spectral resolution; the instrument has an f/number of 3 and a spectral resolution of 0.025 nm. The spectrometer can also operate in survey mode, recording a spectral region of 13 nm with 0.1-nm resolution. Using Doppler broadening of spectral lines, the temperature of deuterium atoms and of C ii and C iii was obtained for L, H, and ELMing H-mode regimes in D iii–D. Using the survey spectrograph, photographic exposures of divertor plasma radiation were obtained spanning the spectral ranges 340–424 and 486–848 nm, in second and first orders of the grating, respectively. The spectrograph is stigmatic and has an f/number of 3. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146300
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  • 9
    Electronic Resource
    Electronic Resource
    Multichord spectroscopy of the DIII-D divertor region : 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. 5167-5169 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multichannel spectrometer with high spectral resolution (0.01 nm) and high temporal resolution (0.5 ms) has been configured to collect data simultaneously from eight viewchords spanning the divertor region of DIII-D. Fiber optically coupled to a wide-field lens with a vertical view of the vessel floor, the instrument will be capable of differentiating the behavior of impurity line emission at the inner and outer divertor strike points, on and off the Advanced Divertor Program ring, on the face of the Divertor Material Exposure System probe, and in the region of the lower centerpost. Used with a coarse grating (300 grooves/mm), spectral coverage of each spatial channel is 15 nm with 0.3 nm resolution; used in high order with a 1200 groove/mm grating, the instrument is capable of resolving Doppler profiles. Spatial variation of gas recycling and impurity influx will be studied for both single- and double-null divertor configurations in low and high density operating regimes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143469
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  • 10
    Electronic Resource
    Electronic Resource
    Argon Kα measurement on DIII–D by Ross filters technique (abstract) : 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. 316-316 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Techniques to reduce the heat flux to the divertor plates in tokamak power plants and the consequent erosion of, and subsequent damage to the divertor target plates include the injection of impurities such as argon, that can dissipate the energy (through radiative or collisional processes) before it reaches the target plates. An important issue with this type of scheme is poisoning of the plasma core by the impurities introduced in the divertor region. Subsequently, there is a desire to measure the profiles of the injected impurities in the core. X-ray Ross filters with an effective narrow band pass centered on the argon Kα line at 3.2 keV, have been installed on two of the existing x-ray arrays on DIII–D in order to help determine the argon concentration profiles. Emissivity profiles of the Kα lines and the emissivity profiles for the argon enhanced continuum can be inferred from the inverted filtered x-ray brightness signals if Te, ne, and Ar18+ profiles are known. The MIST〈citeref RID="R1" STYLE="SUPERIOR"〉1 code is used to couple the filtered x-ray signals to the time dependent measurements of Te and ne. Further, the Ar16+ profiles measured by charge transfer spectroscopy, are used as a constraint on the MIST code runs to calculate Ar18+ profiles and unfold the argon emissivity profiles. A discussion of the Ross filters, the DIII–D argon data, and the data analysis scheme for inferring argon emissivity profiles will be discussed. Estimates of the total argon concentration in the core determined from this technique in DIII–D argon puff experiments will be presented. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149482
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