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  • 1
    Electronic Resource
    Electronic Resource
    Direct ion beam deposition of carbon films on silicon in the ion energy range of 15–500 eV (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5623-5628 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Direct ion beam deposition of carbon films on silicon in the ion energy range of 15–500 eV and temperature range of 25–800 °C has been studied. The work was carried out using mass-separated C+ and CH+3 ions under ultrahigh vacuum. The films were characterized with x-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and transmission electron diffraction analysis. In the initial stage of the deposition, carbon implanted into silicon induced the formation of silicon carbide, even at room temperature. Further carbon ion bombardment then led to the formation of a carbon film. The film properties were sensitive to the deposition temperature but not to the ion energy. Films deposited at room temperature consisted mainly of amorphous carbon. Deposition at a higher temperature, or post-deposition annealing, led to the formation of microcrystalline graphite. A deposition temperature above 800 °C favored the formation of microcrystalline graphite with a preferred orientation in the (0001) direction. No evidence of diamond formation in these films was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350177
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  • 2
    Electronic Resource
    Electronic Resource
    Argon incorporation in Si(100) by ion bombardment at 15–100 eV (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7101-7106 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Argon incorporation in Si(100) by low energy ion bombardment has been studied by polar angle dependent x-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy. The bombardment was performed at 15, 20, and 100 eV in an ultrahigh vacuum chamber where a mass-separated argon ion beam with an energy spread of less than 1 eV was directed to the target. Both the argon penetration depth and incorporation probability were found to increase with bombardment energy. With a fluence of 2×1017/cm2, most of the incorporated argon was located within 20 A(ring) of the target surface for the 100 eV bombardment and within 10 A(ring) for the 15 eV bombardment. In all cases, the argon depth distribution reached a maximum and then declined. At this fluence, the incorporation probabilities were 0.0015 and 0.0004 for the 100 and 15 eV bombardment, respectively. When the amount of incorporated argon was measured as a function of fluence, it increased with fluence at low fluences, reached a quasisaturation at about 1×1016/cm2, but became fluence dependent again above 1×1018/cm2. The retained argon was stable at room temperature but showed at least two stages of thermal desorption in the temperature range 25–500 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355024
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  • 3
    Electronic Resource
    Electronic Resource
    An extreme ultraviolet spectroscopic diagnostic for fluctuations of electron density and temperature in tokamak plasmas (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5511-5518 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extreme ultraviolet (XUV) spectral line emissivities, originating from resonant transitions with upper states excited mainly from ground or both ground and lowest metastable states by electron collisional excitations of highly ionized intrinsic impurities in tokamak plasmas, are linear functions of both electron density and temperature fluctuations, ñe and T˜e, when the fluctuations are small and at high frequency. Correlations between measured intensities of spectral lines can thus provide localized measurements of the fluctuations. Newly developed XUV monochromators of high throughput enable accurate and fast diagnostics of ñe and T˜e for the study of the tokamak plasma microturbulence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347010
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  • 4
    Electronic Resource
    Electronic Resource
    Finite-β and alpha particle effects on kinetic Alfvén wave in a fusion tokamak plasma (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2293-2305 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper, a model for the kinetic Alfvén wave (KAW) in the presence of fusion alphas is established. The finite-β (relative to low β) and alpha particle effects on KAW are investigated. In this model, ion sound, transit time magnetic pumping (TTMP), the response of alpha particles (alphas), and those effects considered by preceding authors are included. In cylindrical geometry, a set of three second-order differential equations in r for the perturbed fields Er, E⊥, and E(parallel) is numerically solved. A dispersion relation of the Alfvén wave in the fusion tokamak plasma is derived. The mode conversion and the energy deposition are qualitatively discussed on the basis of this relation. Both the analytical and numerical analyses indicate that (i) no matter whether m (poloidal mode number) is positive [N. Ding et al., Phys. Plasmas 2, 1529 (1995)] or negative (mainly studied in the present paper), the alphas do not affect the compressional Alfvén wave, but they do affect the KAW evidently; (ii) for m〈0, it is preferable to choose the frequency ω of the injected wave so that the inequality ω(approximately-greater-than)(Pm±1/Rm±1)−1ω*αm holds for optimal power absorption. The energy deposition at the resonant position close to the interior of the fusion tokamak plasma in taking account of the effects of ion sound and TTMP is less than that without taking account of these effects. But for the same β value, at the position adjacent to the edge the contrary is the case. For a certain resonant position, as the β value increases, the energy deposition decreases. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871912
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  • 5
    Electronic Resource
    Electronic Resource
    Trapped ion temperature gradient driven instabilities with bounce resonance (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3757-3763 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A kinetic analysis of ion temperature gradient modes with the trapped ion bounce resonance in tokamaks is presented under the long-wavelength limit. The dispersion relations of the toroidal and slab branches are derived by employing two-scale expansion, and their eigenfunctions are obtained analytically. The growth rates and stability thresholds of the more unstable toroidal and slab ion modes are evaluated in the cases with and without trapped electron dynamics. It is found that the minority trapped ion bounce resonances possess approximately the same effects on the toroidal and slab ion modes as the majority ion transit resonances. The nonadiabatic trapped electron dynamics does also strongly affect the toroidal ion mode while it affects the slab branch, the trapped electrons have a destabilizing effect on these ion modes. In addition, the effects of trapped electron temperature gradient on the trapped ion temperature gradient modes are considered. For high collisionality, the trapped electron temperature gradient destabilizes toroidal and slab ion modes. On the contrary, it plays a role of stabilizing to the toroidal and slab ion modes in the case of very low collisionality. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871445
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of energetic ions on kinetic Alfvén wave in a tokamak plasma (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1529-1539 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of energetic ions on the electric field structure and the energy deposition of kinetic Alfvén wave (KAW) in a tokamak plasma are considered. A cylindrical geometry is adopted and a linearized kinetic model including the bulk plasma and the energetic ions is established. These effects of fusion alpha particles (abbreviated, alphas) in deuterium–tritium (D–T) tokamak plasmas are numerically analyzed. The energetic ions tend to alter the wave structure and the energy deposition. The absorption of the kinetic Alfvén wave by the bulk plasma depends sensitively on both the velocity distribution of alphas and the spatial profile of the alpha particle density, as well as on the frequency of the injected wave. Numerical results of the wave structure and the power absorption are given for the parameters of D–T plasmas. The present studies lead to the following discoveries: (1) The slowing-down alpha particle distribution reduces the KAWs energy deposition and the Maxwellian alphas have hardly any influence over it; (2) the more the (slowing-down) alphas near the resonant layer, the more heavily they prevent the KAWs power absorption by the bulk plasma; (3) the lower frequency of the injected wave within the range of KAWs continuum, the more heavily the KAWs structure and power absorption by the bulk plasma are affected by alpha particles; and (4) the energy deposition decreases rapidly as the total number of alphas increases. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871368
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  • 7
    Electronic Resource
    Electronic Resource
    Laboratory test of a LSM-based narrow bandpass and high throughput camera for Tokamak plasma imaging between 100 and 200 A(ring) : 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. 5171-5173 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A narrow-bandpass (∼7 A(ring)) and high-throughput (f/5.5) extreme ultraviolet (XUV) camera using layered synthetic microstructure (LSM) coated optics has been built and tested at the Johns Hopkins University laboratory in order to image tokamak plasma emission between 100 and 200 A(ring). The LSM camera was tested with a Penning ionization discharge emission source. The test measures the spectral bandpass, the spatial resolution, and the relative photosensitivities. The XUV camera will be used to measure the O vi 150 A(ring) line brightness on the Phaedrus-T tokamak with a tangential view to investigate the impurity transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143471
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  • 8
    Electronic Resource
    Electronic Resource
    Narrow bandpass layered synthetic microstructure-based pinhole camera to image a tokamak plasma in H-like carbon emission at 34 A(ring) : 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. 5174-5175 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The layered synthetic microstructure (LSM) technology has made two-dimensional soft x-ray imaging of a tokamak plasma in a single impurity spectral line emission feasible. The curved LSM is used both as an optical filter, with a bandpass in the range of interest on the order of 1.5 A(ring), and as a focusing optic. A detailed design of a narrow bandpass curved LSM-based pinhole camera, which will image the the region from the scrape-off layer 26 cm into the plasma in the DIII-D tokamak plasma in C vi Lyman α emission at 34 A(ring), will be presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143472
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  • 9
    Electronic Resource
    Electronic Resource
    A polarimeter for localized continuous measurement of the poloidal magnetic field in a tokamak (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1142-1148 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A polarimeter for the circular polarization of Zeeman-split spectral line emissions has been developed to measure the poloidal magnetic field in tokamak plasmas. The Li I 6708 A(ring) line originating from a monoenergetic lithium beam provided a localized spectral source. In the polarimeter, interference filters of narrow bandpass were set at the peak wavelength of the circular polarization, enabling the measurement to be continuous and sensitive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142515
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  • 10
    Electronic Resource
    Electronic Resource
    A possible hybrid dissipative trapped electron ion temperature gradient mode (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3004-3012 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of dissipative trapped electrons on ion temperature gradient-driven instability (ηi mode) in tokamak plasmas are considered. A sheared slab geometry is adopted and a linearized fluid model of ion temperature gradient (ITG) mode including dissipative trapped electrons, which are described by means of the well-known formula of the nonadiabatic electron response [P. L. Similon and P. H. Diamond, Phys. Fluids 27, 916 (1984)], is presented. Results show that in tokamak plasmas not only is there a modification of the dissipative trapped electrons on the ηi mode, but also there may exist an intrinsic oscillation mode, namely, a hybrid dissipative trapped electron ion temperature gradient mode. The higher the dissipative trapped electron fraction, the more it drives the ηi mode, that is, when the trapped electron fraction is sufficient high and the trapped electrons are dissipated strongly, the mode is dominated by the trapped electron dynamics and propagates in the electron diamagnetic direction. These analytical results can be reduced to the usual predictions of the ion temperature gradient-driven instability in the absence of the dissipative trapped electron. Numerical results further show that (a) there may be a hybrid dissipative trapped electron ITG mode and the dissipative trapped electron effect is a destabilizing effect on this mode; and (b) when the trapped electron fraction is sufficiently high and the trapped electrons are dissipated strongly, the mode is determined by the trapped electron dynamics. These conclusions are in agreement with the experimental observations in the latest simulated tokamak experiment on the Columbia Linear Machine [J. Chen and A. K. Sen, Phys. Rev. Lett. 72, 3997 (1994)]. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871635
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