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  • 1990-1994  (41)
  • 1994  (25)
  • 1992  (16)
  • 1
    Electronic Resource
    Electronic Resource
    Adhesion and mechanical properties of amorphic diamond films prepared by a laser plasma discharge source (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1446-1453 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphic diamond films can be grown in an ultrahigh vacuum environment free from hydrogen with a laser plasma discharge source. This technique produces films that adhere more readily to materials for which there are important applications as protective coatings. In this work adhesion and mechanical properties of amorphic diamond films have been examined. A beam bending method has been used to measure the internal stress and a relatively low value of compressive stress was found. The dependence of stress on the laser intensities at the graphite ablation target has been studied. Analyses of these films on silicon, SiO2, ZnS, and TiAl6V4 by Rutherford backscattering spectrometry show significant interfacial layers with compositions of SiC, C0.5SiO2, C2.5ZnS, and C0.62Ti0.35Al0.05V0.02, respectively. Adhesion properties on ZnS and other substrates have also been examined for harsh environments. The mechanical properties of hardness, Young's modulus, and stiffness have been obtained with a nanoindentation technique. These results together with the minimal amount of hydrogen in our process, make amorphic diamond an excellent candidate for direct deposition on several substrates including ZnS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351267
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructural analyses of amorphic diamond, i-C, and amorphous carbon (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 239-245 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent experiments have identified the microstructure of amorphic diamond with a model of packed nodules of amorphous diamond expected theoretically. However, this success has left in doubt the relationship of amorphic diamond to other noncrystalline forms of carbon. This work reports the comparative examinations of the microstructures of samples of amorphic diamond, i-C, and amorphous carbon. Four distinct morphologies were found that correlated closely with the energy densities used in preparing the different materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352168
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  • 3
    Electronic Resource
    Electronic Resource
    The bonding of protective films of amorphic diamond to titanium (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3260-3265 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Films of amorphic diamond can be deposited from laser plasma ions without the use of catalysts such as hydrogen or fluorine. Prepared without columnar patterns of growth, the layers of this material have been reported to have "bulk'' values of mechanical properties that have suggested their usage as protective coatings for metals. Described here is a study of the bonding and properties realized in one such example, the deposition of amorphic diamond on titanium. Measurements with Rutherford backscattering spectrometry and transmission electron microscopy showed that the diamond coatings deposited from laser plasmas were chemically bonded to Ti substrates in 100–200-A(ring)-thick interfacial layers containing some crystalline precipitates of TiC. Resistance to wear was estimated with a modified sand blaster and in all cases the coating was worn away without any rupture or deterioration of the bonding layer. Such wear was greatly reduced and lifetimes of the coated samples were increased by a factor of better than 300 with only 2.7 μm of amorphic diamond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351390
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  • 4
    Electronic Resource
    Electronic Resource
    Growth of CdTe epitaxial films on p-InSb(111) by temperature gradient vapor transport deposition (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1049-1051 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of high quality CdTe epitaxial films on p-InSb(111) by a simple method of temperature gradient vapor transport deposition was carried out to investigate the possibility of the existence of a two-dimensional electron gas with high mobility at CdTe/InSb heterointerfaces. From the x-ray diffraction analysis, the grown layer was found to be a CdTe epitaxial film. Photoluminescence measurements at 15 K showed that a CdTe film grown on InSb(111) in the temperature range between 180 and 280 °C appeared to have an optimum crystal perfection at a substrate temperature of about 245 °C. These results also indicated that the CdTe films grown above 245 °C contained a significant problem due to interdiffusion from the InSb substrates during the growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351360
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  • 5
    Electronic Resource
    Electronic Resource
    Performance evaluation of the TFTR gyrotron CTS diagnostic for alpha particles : 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. 4644-4646 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A large-angle, 60-GHz collective Thomson scattering (CTS) diagnostic system for localized measurements of DT alpha-particle velocity distribution and fraction is being implemented on TFTR. Calculations of expected CTS spectra, signal-to-noise ratio per receiver channel, and estimated error in determining the temperature and fraction of alpha particles are being carried out. The experimental spectra are simulated by adding noise to the theoretical calculation by a Monte Carlo technique. Error analysis is then performed by using a relative intensity calibrated nonlinear curve fitting code to calculate the desired plasma parameters (Ti, Tα, nα/ni). Simulation results indicate that expected background emission of 20 eV during Supershot in TFTR poses no problem to the experiment. Also short integration times (〈10 ms) can be used to resolve the energetic ion features, thus offering a possibility for the study of temporal evolution of energetic ion velocity distribution during a single plasma shot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143646
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  • 6
    Electronic Resource
    Electronic Resource
    Characteristics of gyrotron scattering system for α particle diagnostics in TFTR (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. 4647-4647 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In D-T plasmas, the understanding of the physics of confined α particles is extremely valuable for the future fusion plasma device. Among the various proposed α diagnostics, an X-mode collective Thomson scattering system employing a high-power gyrotron source (P(approximately-equal-to)200 kW, f=60 GHz, pulse length (approximately-equal-to)0.5 s, and modulation frequency=10–25 kHz) is being designed for TFTR. The detailed description of the gyrotron source, transmission lines, optical designs, beam and viewing dump design, and receiver system will be presented in this paper. In particular, the test results of the beam and viewing dump indicate that the stray light can be reduced by 60 dB. The background emission level (∼20 eV) near 60-GHz range during high Q discharge may also be reduced with beam and viewing dump further. The optical system is designed to measure the radial profile of α particles and to orient the incident wavevector (k0) to test the electromagnetic effects of the scattered spectrum. Prior to the study of α physics in D-T plasmas, this scattering system will be used to measure not only a bulk ion temperature but also the scattered spectrum due to fast ions produced by NB and ICRF heating in TFTR. This work was supported by the U.S. Department of Energy Contract No. DE-AC02-76-CHO-3073.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143647
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  • 7
    Electronic Resource
    Electronic Resource
    Lithium pellet deposition and penetration in TFTR : 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. 4984-4986 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The electron deposition resulting from the injection of Li pellets into Tokamak Fusion Test Reactor, measured by a multichannel (10) infrared interferometer, is compared with that deduced from the pellet ablation cloud emission, measured by a filtered diode array which views the pellet from behind. By assuming that the ablation rate N(overdot)(r) is proportional to the pellet cloud emissivity, which is dominated by Li+ line emission in the 548.5±5 nm bandpass of the interference filter, the post-pellet, line averaged density perturbations along the interferometer chords were calculated and compared with those measured. Good agreement is observed. The experimental ablation rate profiles obtained using the emissivity have also been compared with predictions of the theoretical models. There is an agreement between the time history of the emissivity and the predicted ablation rate at the plasma edge where the electron temperature values are less than 1–1.5 keV. When the pellet penetrates more deeply, the experimental N(overdot)(r) values are systematically smaller than those predicted. This points out the necessity of taking into account plasma shielding and/or precooling of the target plasma during pellet injection in the ablation model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143521
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  • 8
    Electronic Resource
    Electronic Resource
    Abel-inversion method for interferometry data in highly noncircular plasmas with X point in TFTR (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. 4763-4763 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In TFTR plasmas, reliable and accurate time-dependent electron density profiles are routinely available via an Abel inversion of interferometry measurements [H. Park, Plasma Phys. Controlled Fusion 31, 2035 (1989)]. This technique does not require constancy of density on a equiflux surface and mild deviations of the flux surfaces from a circular shape are accommodated through analytic approximations. However, when the flux surfaces become extremely noncircular as the plasma β is increased significantly, the inverted profiles are not consistent with the Thomson scattering measurements. In order to obtain accurate time-dependent density profiles in high-β plasmas, detailed flux surface information from magnetic measurements must be used to invert the interferometric measurements. The basic inversion process is similar but the scrape-off layer treatment is different when an X point is introduced on the high field side. In this paper, we present a comparison between the inverted profiles obtained with the flux-surface data and with the analytic method. This work supported by U. S. Department of Energy Contract No. DE-AC02-76-CHO-3073.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143633
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  • 9
    Electronic Resource
    Electronic Resource
    Scaling of Ohmic energy confinement with major radius in the Tokamak Fusion Test Reactor (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 3996-4001 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ohmic plasma size scans have been carried out in the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)] to measure the influence of the major radius upon energy confinement. The major radius, minor radius, and aspect ratio were varied over wide ranges (R=2.08–3.2 m, a=0.4–0.9 m, and R/a=2.9–8.0) at constant qc. The energy confinement determined from kinetic diagnostics varies strongly with major radius. The data set is less well suited to determine minor radius scaling, but it appears to be distinctly weaker than the major radius scaling. The anomaly in ion thermal conductivity over neoclassical predictions appears to decline with increasing aspect ratio, which is a better ordering parameter for the magnitude of the anomaly than either the minor radius or the major radius. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870869
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  • 10
    Electronic Resource
    Electronic Resource
    Structural and optical properties in ZnTe/GaAs strained heterostructures grown by temperature-gradient vapor transport deposition (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 8216-8218 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A lattice-mismatched ZnTe epilayer on a GaAs(100) substrate was grown by the simple method of temperature-gradient vapor deposition. X-ray diffractometry measurements were performed to investigate the structural properties of the ZnTe layer. Raman spectroscopy measurements showed that there was a lattice mismatch between the ZnTe epitaxial layer and the GaAs substrate. Reflectivity and photoreflectance measurements clearly revealed the splitting of the valence-band maximum, and photoluminescence measurements showed several resonant excitations of the ZnTe. The binding energies of the light holes and heavy holes determined from the splittings are in reasonable agreement with the bulk values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356526
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