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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 895-906 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A multichannel vacuum Bragg-crystal spectrometer has been developed for high-resolution measurements of the line emission from tokamak plasmas in the wavelength region between 4 and 25 A(ring). The spectrometer employs a bent crystal in Johann geometry and a microchannel-plate-intensified photodiode diode array. The instrument is capable of measuring high-resolution spectra (λ/Δλ≈3000) with fast time resolution (4 ms per spectrum) and good spatial resolution (3 cm). The spectral bandwidth is Δλ/λ0=15% at λ0=8 A(ring). A simple tilt mechanism allows access to different wavelength intervals. In order to illustrate the utility of the new spectrometer, time- and space-resolved measurements of the n=3–2 spectrum of selenium from the Princeton Large Torus tokamak plasmas are presented. The data are used to determine the plasma transport parameters and to infer the radial distribution of fluorinelike, neonlike, and sodiumlike ions of selenium in the plasma. The new ultrasoft x-ray spectrometer has thus enabled us to demonstrate the utility of high-resolution L-shell spectroscopy of neonlike ions as a fusion diagnostic.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1518-1520 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Charge exchange recombination spectroscopy has been used to observe transitions originating from hydrogen-, helium-, and lithiumlike charge states of medium-Z metallic impurities in TFTR. The temporal and spatial densities of these ions were measured in ohmic and neutral beam heated plasmas. These preliminary results agree with predictions of a transport code.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 1837-1844 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A theoretical upper limit for the density in an Ohmically heated tokamak discharge follows from the requirement that the Ohmic heating power deposited in the current-carrying channel exceed the impurity radiative cooling in this critical region. A compact summary of our results gives this limit nM for the central density as nM =[Ze/(Ze−1)]1/2 ne0 (BT /1T) (1m/R), where ne0 depends strongly on the impurity species and is remarkably independent of the central electron temperature Te(0). For Te(0) ∼1 keV, ne0 =1.5×1014 cm−3 for beryllium, ne0 =5.5×1013 cm−3 for oxygen, ne0 =1.0×1013 cm−3 for iron and, ne0 =0.5×1013 cm−3 for tungsten. The results agree quantitatively with Murakami's original observations. A similar density limit, known as the I/N limit, exists for reversed-field pinch devices and this limit has also been evaluated for a variety of impurity species.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Results from helium, iron, and electron transport studies on the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Res. 26, 11 (1984)] in L-mode and supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal transport analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the electron channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the supershot. The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the supershot, differences are found in the L mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the electron heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to electron heat flux can be more than a factor of 3 larger than experimental values. A correlation between helium diffusion and ion thermal transport is observed and has favorable implications for sustained ignition of a tokamak fusion reactor.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1572-9591
    Schlagwort(e): diagnostics ; alpha particles ; tokamak ; fusion diagnostics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Methods are proposed for measuring the alpha-particle distribution in magnetically confined fusion plasmas using neutral-atom doping beams, ultraviolet spectroscopy, and neutral particle detectors. In the first method, single charge exchange reactions, A0+He2+→A+ +(He+)*, are used to populate then=2 andn=3 levels of He+. The ultraviolet photons from the decaying excited states are Doppler shifted by 5–10 Å from those produced by the thermalized alpha-particle “ash.” In the second method, double charge exchange reactions, A0+He2+→A2++He0, enable fast neutralized alpha particles to escape from the plasma and be detected by neutral particle analyzers. These methods are distinguished from similar techniques of observing plasma impurities in that, in principle, they allow a determination of the dependence of the distribution function on energy and pitch angle, as well as on spatial position. Detector configurations are analyzed, count rates are estimated, and the detector feasibility is discussed. A preliminary analysis of the feasibility of the required neutral beams is presented, and exploratory experiments on existing devices are suggested.
    Materialart: Digitale Medien
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