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  • 1
    Digitale Medien
    Digitale Medien
    A fast charge coupled device detector for charge exchange recombination spectroscopy on the DIII-D Tokamak (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1233-1237 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Charge exchange recombination (CER) spectroscopy has become a standard diagnostic for Tokamaks. CER measurements have been used to determine spatially and temporally resolved ion temperature, toroidal and poloidal ion rotation speed, impurity density, and radial electric field. Knowledge of the spatial profile and temporal evolution of the electric field shear in the plasma edge is crucial to understanding the physics of the L to H transition. High speed CER measurements are also valuable for edge localized mode studies. Since the 0.52 ms minimum time resolution of our present system is barely adequate to study the time evolution of these phenomena, we have developed a new charge coupled device (CCD) detector system with about a factor of 2 better time resolution. In addition, our existing system detects sufficient photons to utilize the shortest time resolution only under exceptional conditions. The new CCD detector has a quantum efficiency of about 0.65, which is a factor of 7 better than our previous image intensifier-silicon photodiode detector systems. We have also equipped the new system with spectrometers of lower f/number. This combination should allow more routine operation at the minimum integration time, as well as improving data quality for measurements in the divertor-relevant region outside of the separatrix. Construction details, benchmark data, and initial Tokamak measurements for the new system will be presented. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147895
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  • 2
    Digitale Medien
    Digitale Medien
    Prospects for charge-exchange-recombination-based measurements on International Thermonuclear Experimental Reactor using a helium diagnostic neutral beam : 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. 886-889 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Several important measurements in the International Thermonuclear Experimental Reactor (ITER) diagnostic mission, including the primary one of core helium ash density, are expected to be addressed using active spectroscopic techniques. These methods rely on the use of a dedicated diagnostic neutral beam (DNB) which has been optimized for the dual requirements of beam penetration and charge exchange cross section. For hydrogenic beams, this results in an optimal beam energy of ∼100 keV/amu. Signal-to-noise estimates using realistic geometries and the existing ITER profile and equilibrium data have confirmed the stringent requirements on beam quality and intensity to satisfy the stated ITER measurement precisions. In this article we consider the use of a neutral helium DNB for making active spectroscopic measurements on ITER, since helium beams offer better penetration in dense plasma for a given energy, and the prospects for given source performance may also be improved. Drawbacks include the more difficult absolute calibration of the beam density profile as well as the fundamental problem of uniquely identifying the source (fusion-based ash, beam core fuelling, or edge DNB neutralizer/source efflux) of the observed He charge-exchange recombination line in order to unambiguously characterize core helium buildup and confinement on ITER. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1149408
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  • 3
    Digitale Medien
    Digitale Medien
    Diagnostics for advanced tokamak research (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. 906-914 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Advanced tokamak research seeks to find the ultimate potential of the tokamak as a magnetic confinement system. Achieving this potential involves optimizing the plasma cross-sectional shape, current density, and pressure profiles for stability to magnetohydrodynamic (MHD) modes while simultaneously controlling the current density, pressure, and radial electric field profiles to minimize the cross field transport of plasma energy. In its ultimate, steady-state incarnation, the advanced tokamak also requires pressure profiles that have been adjusted to achieve the maximum possible bootstrap current, subject to the constraints of MHD stability. This simultaneous, nonlinear optimization of shape, current, pressure, and electric field profiles to meet multiple goals is a grand challenge to plasma physics. To keep the plasma at peak performance, active feedback control will almost certainly be required. Diagnostic measurements play a crucial role in advanced tokamak research both for developing the scientific understanding underlying the optimization and for serving as sensors for real time feedback control. One outstanding example of this is the way motional Stark effect (MSE) measurements of the internal magnetic field revolutionized work on current profile shaping. Improved diagnostic measurements are essential in testing theories which must be validated in order to apply advanced tokamak results to next step devices. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1321006
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  • 4
    Digitale Medien
    Digitale Medien
    Enhanced spatial localization of collective scattering measurements in the DIII-D tokamak : 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. 848-850 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Collective scattering measurements on DIII-D have been complicated by significant toroidal and poloidal plasma rotation which produces large and inhomogeneous radial electrical fields which in turn Doppler shift the spectra of the scattered radiation. From independent measurements of the radical electric field profile, the radial variation of the fluctuation magnitude can be approximated from the frequency spectrum of the scattered radiation so the improved resolution is related to the scale length of the radial electrical field. Such improved spatial resolution will allow the interaction between local gradients and the fluctuation level to be investigated in more detail. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1146246
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  • 5
    Digitale Medien
    Digitale Medien
    Enhanced spatial localization of collective scattering based on spatially varying electric fields (abstract) : 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. 4636-4636 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Collective scattering measurements on DIII-D have been complicated by the large toroidal and polodial plasma rotation which results in a large spatially varying radial electric field, especially during neutral beam injection and H mode. This electric field produces a Doppler shift (via Er×B rotation) of the scattered spectra which usually dominates the measured phase velocity and depends strongly on plasma conditions and radial variations of the electric field. Measurements from charge exchange recombination spectroscopy allow the radial structure of Er to be independently determined. The strong variation of the radial electric field across the plasma has allowed unambiguous mapping of different frequency bands of the scattered spectra into different locations in the plasma. Thus, the characteristics of fluctuations originating from the plasma interior can be easily distinguished from the edge. Measurements of the radial variation of the turbulent fluctuations will be presented. This work is supported by the U.S. Department of Energy (DOE) under Grant No. DE-FG03-86-ER53225 and DOE Contract No. DE-AC03-89ER51114.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1143642
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  • 6
    Digitale Medien
    Digitale Medien
    A global fitting code for multichordal neutral beam spectroscopic data : 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. 4764-4767 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Knowledge of the heat deposition profile is crucial to all transport analysis of beam heated discharges. The heat deposition profile can be inferred from the fast ion birth profile which, in turn, is directly related to the loss of neutral atoms from the beam. This loss can be measured spectroscopically by the decrease in amplitude of spectral emissions from the beam as it penetrates the plasma. The spectra are complicated by the motional Stark effect which produces a manifold of nine bright peaks for each of the three beam energy components. A code has been written to analyze these kinds of data. In the first phase of this work, spectra from tokamak shots are fit with a Stark splitting and Doppler shift model that ties together the geometry of several spatial positions when they are fit simultaneously. In the second phase, a relative position-to-position intensity calibration will be applied to these results to obtain the spectral amplitudes from which beam atom loss can be estimated. This paper reports on the computer code for the first phase. Sample fits to real tokamak spectral data are shown.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1143634
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  • 7
    Digitale Medien
    Digitale Medien
    Improved charge coupled device detectors for the edge charge exchange spectroscopy system on the DIII-D tokamak : 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. 1028-1033 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Charge exchange spectroscopy is one of the key ion diagnostics on the DIII-D tokamak. It allows measurement of impurity densities, toroidal and poloidal rotation speeds, ion temperatures, and the radial electric field. For the 2000 experimental campaign, we have replaced the intensified photodiode array detectors on the edge portion of the system with advanced charge-coupled device (CCD) detectors mounted on faster (f/4.7) Czerny–Turner spectrometers equipped with toroidal mirrors. The combination has improved the photoelectron signal level by about a factor of 20 and the signal to noise by a factor of 2–8, depending on the absolute signal level and readout mode. A major portion of the signal level improvement comes from the improved quantum efficiency of the back-illuminated, thinned CCD detector (70% to 85% quantum efficiency for the CCD versus 10% for the image intensifier) with the remainder coming from the faster spectrometer. The CCD camera also allows shorter minimum integration times: 0.33 ms while archiving to computer memory and 0.15 ms using temporary storage on the CCD chip. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1319363
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  • 8
    Digitale Medien
    Digitale Medien
    Prospects for edge current density determination using LIBEAM on DIII-D : 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. 1023-1027 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The specific size and structure of the edge current profile has important effects on the magnetohydrodynamic stability and ultimate performance of many advanced tokamak (AT) operating modes. This is true for both bootstrap and externally driven currents that may be used to tailor the edge shear. Absent a direct local measurement of j(r), the best alternative is a determination of the poloidal field. Measurements of the precision (0.1°–0.01° in magnetic pitch angle and 1–10 ms) necessary to address issues of stability and control and provide constraints for EFIT are difficult to do in the region of interest (ρ=0.9–1.1). Using Zeeman polarization spectroscopy of the 2S–2P lithium resonance line emission from the DIII-D LIBEAM [D. M. Thomas, Rev. Sci. Instrum. 66, 806 (1995); D. M. Thomas, A. W. Hyatt, and M. P. Thomas, Rev. Sci. Instrum. 61, 340 (1990)] measurements of the various field components may be made to the necessary precision in exactly the region of interest to these studies. Because of the negligible Stark mixing of the relevant atomic levels, this method of determining j(r) is insensitive to the large local electric fields typically found in enhanced confinement (H mode) edges, and thus avoids an ambiguity common to motional Stark effect measurements of B. Key issues for utilizing this technique include good beam quality, an optimum viewing geometry, and a suitable optical prefilter to isolate the polarized emission line. A prospective diagnostic system for the DIII-D AT program will be described. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1319612
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  • 9
    Digitale Medien
    Digitale Medien
    Wavelength calibration of the charge exchange recombination spectroscopy system on the DIII-D tokamak : 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. 878-881 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A wavelength calibration of all the detectors on the charge exchange recombination spectroscopy system is performed after every plasma discharge on the DIII-D tokamak. This is done to insure that the rest of the wavelength position of the C VI 5290.5 Å charge exchange line on the detector is accurately known so that the Doppler shift of the spectral line emitted during the discharge can be used for measurements of plasma rotation. In addition, this calibration provides a check on the spectral dispersion needed to determine the ion temperature. The reference spectra for the calibration are Ne I lines created by neon capillary discharge lamps contained within specially designed diffuse reflectors. The Ne I lines at 3520.4720, 5274.0393, 5280.0853, 5298.1891, and 5304.7580 Å are used in this work. The location of these lines on the linear detectors can be determined to an accuracy of 0.1 pixel, which corresponds to a plasma rotation accuracy of 1.2 and 0.7 km/s for the central and edge rotation measurements, respectively. Use of oppositely directed views of the plasma at the same major radius have been used to verify that the nominal 5290.5 Å wavelength of the C VI (n=8–7) multiplet is the correct wavelength for the line emitted owing to charge exchange excitation. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1149288
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  • 10
    Digitale Medien
    Digitale Medien
    A fast charge coupled device detector for charge exchange recombination spectroscopy on the DIII-D Tokamak (abstract) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1019-1019 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Charge exchange recombination (CER) spectroscopy has become a standard diagnostic for Tokamaks. CER measurements have been used to determine spatially and temporally resolved ion temperature, toroidal and poloidal ion rotation speed, impurity density, and radial electric field. Knowledge of the spatial profile and temporal evolution of the electric field shear in the plasma edge is crucial to understanding the physics of the L to H transition. High speed CER measurements are also valuable for edge localized mode studies. Since the 0.52 ms minimum time resolution of our present system is barely adequate to study the time evolution of these phenomena, we have developed a new charge coupled device (CCD) detector system with about a factor of 2 better time resolution. In addition, our existing system detects sufficient photons to utilize the shortest time resolution only under exceptional conditions. The new CCD detector has a quantum efficiency of about 0.65, which is a factor of 7 better than our previous image intensifier-silicon photodiode detector systems. We have also equipped the new system with spectrometers of lower f/number. This combination should allow more routine operation at the minimum integration time, as well as improving data quality for measurements in the divertor-relevant region outside of the separatrix. Construction details, benchmark data, and initial Tokamak measurements for the new system will be presented. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147825
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