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  • 1990-1994  (45)
  • 1985-1989  (45)
  • 1870-1879  (1)
  • 1
    Digitale Medien
    Digitale Medien
    The structural homogeneity of boron carbide thin films fabricated using plasma-enhanced chemical vapor deposition from B5H9+CH4 (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6919-6924 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Boron carbide thin films of several B/C ratios have been deposited on Si(111) using plasma-enhanced chemical vapor deposition from nido-pentaborane(9) (B5H9) and methane (CH4). X-ray diffraction studies of boron carbide thin films on Si(111) exhibited characteristic microcrystalline diffraction lines. Soft x-ray emission spectroscopy was used to verify that the local electronic structure and composition of each sample corresponded to a homogeneous solid solution boron carbide phase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.355066
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  • 2
    Digitale Medien
    Digitale Medien
    A soft-x-ray-emission investigation of cobalt implanted silicon crystals (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7800-7804 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The Si L2,3 emission spectra of silicon crystals implanted with Co at doses of (1–8) × 1017 Co/cm2 have been examined using soft-x-ray-emission (SXE) spectroscopy. At the lowest dose, the spectra are little modified from that of crystalline Si, indicating that only a small fraction of Si is in the form of silicides within the probe depth of SXE spectroscopy. For higher doses and implant profiles with Co extending to the surface, there is clear evidence for ordered CoSi2 combined with richer Co phases, but little evidence for pure Si or for ordered regions of CoSi.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347508
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  • 3
    Digitale Medien
    Digitale Medien
    Proton spin–lattice relaxation rate in supercooled H2O and H2 17O under high pressure (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4796-4803 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The proton spin–lattice relaxation rate has been investigated as a function of pressure (p≤250 MPa), temperature (180 K≤T≤300 K), and oxygen-17 enrichment (25.7 atom-%, 50.7 atom-%) in metastable water. Intramolecular proton–oxygen 17 dipolar interactions in light water in relation to deuterium electric quadrupole interactions in heavy water carry similar dynamic information and allow the complicated dynamic isotope effect in liquid water to be investigated in the whole metastable range. Under hydrostatic pressure the proton relaxation rate curve R1 (T, p, ωH) has been investigated at five different Larmor frequencies (100 MHz≤ω≤500 MHz). These experiments unequivocally prove the isotropy of reorientational motions of water molecules on a nanosecond time scale and demonstrate the necessity to include fast quasilattice vibrations into a consistent interpretation of the relaxation rates in the dispersion regime.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.458670
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  • 4
    Digitale Medien
    Digitale Medien
    Core level photoemission of iodine overlayers (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 4406-4411 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We report the core level binding energies of chemisorbed iodine on Fe(110) and Fe(100). A decrease of 0.6 eV in the binding energies of the iodine core levels is observed with the increasing coverage of the chemisorbed iodine overlayer. This change in core level binding energies with coverage is compared with the results for iodine overlayers on other transition metal surfaces. The difference in core level binding energies between chemisorbed iodine on Fe(110) and molecularly adsorbed iodine on Fe(110) is explained using a Born–Haber cycle and an "equivalent'' cores approximation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.454826
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  • 5
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.870869
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  • 6
    Digitale Medien
    Digitale Medien
    PLT and PDX perpendicular charge exchange analyzers (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1794-1796 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The perpendicular charge-exchange systems used on the poloidal divertor experiment and the Princeton large torus are comprised of ten-channel, mass-resolved, charge-exchange analyzers. Results from these systems indicate that instrumental effects can lead to erroneous temperature measurements during deuterium neutral beam injection or at low hydrogen concentrations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1139185
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  • 7
    Digitale Medien
    Digitale Medien
    Magnetic diagnostics and feedback control on TFTR (invited) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 941-946 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The various operating modes of TFTR require the use of a sophisticated system of magnetic diagnostics integrated with a feedback control system. This system has successfully controlled the plasma current and position over a range of major and minor radii, during strong compression, and will soon be used during intense neutral beam heating. Current and position values are held constant to within 2 kA and 1 cm. A wide variety of preoperational field measurements were required to determine proper compensation for dynamic stray fields due to eddy currents. Data from plasma profile diagnostics, such as bolometer arrays, Thomson scattering, soft x-ray diode array, and the scanning radiometer, have been compared to the absolute position deduced from magnetics. In addition to control functions, magnetic diagnostics on TFTR provide data on plasma current asymmetry, βθ, MHD fluctuations, loop voltage, and flux consumption. This paper will discuss the mechanical and electronic design constraints, as well as the analytic and calibration techniques required.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1138056
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  • 8
    Digitale Medien
    Digitale Medien
    Possible origin of the anomalous magnetization behavior in melt-textured Y1Ba2Cu3O7−δ crystallites (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 406-408 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magnetization measurements of the hysteresis loop, M(B), of melt-textured Y1Ba2Cu3O7−δ (YBCO) crystallites were performed in external magnetic fields up to 10 T. The M(B) curves exhibit, between the superconducting transition temperature Tc and almost 39 K, a peak at a finite field B* which increases with decreasing temperature. The crystallites possess a high density of dislocations which could have been introduced during the high temperature treatment and/or by stresses created due to differences in the lattice parameter of small inclusions and the YBCO matrix. The large dislocation density together with the high sensitivity of the superconducting order parameter on deviations from the regular crystal structure and the small coherence length are suggested to be responsible for the observed fishtail shape of the magnetization curves.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.110033
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  • 9
    Digitale Medien
    Digitale Medien
    High poloidal beta equilibria in the Tokamak Fusion Test Reactor limited by a natural inboard poloidal field null (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2277-2284 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Recent operation of the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Research 1, 51 (1986)] has produced plasma equilibria with values of Λ≡βp eq+li/2 as large as 7, εβp dia≡2μ0ε〈p⊥〉/〈〈Bp〉〉2 as large as 1.6, and Troyon normalized diamagnetic beta [Plasma Phys. Controlled Fusion 26, 209 (1984); Phys. Lett. 110A, 29 (1985)], βNdia≡108〈βt⊥〉aB0/Ip as large as 4.7. When εβp dia(approximately-greater-than)1.25, a separatrix entered the vacuum chamber, producing a naturally diverted discharge that was sustained for many energy confinement times, τE. The largest values of εβp and plasma stored energy were obtained when the plasma current was ramped down prior to neutral beam injection. The measured peak ion and electron temperatures were as large as 24 and 8.5 keV, respectively. Plasma stored energy in excess of 2.5 MJ and τE greater than 130 msec were obtained. Confinement times of greater than 3 times that expected from L-mode predictions have been achieved. The fusion power gain QDD reached a value of 1.3×10−3 in a discharge with Ip=1 MA and εβp dia=0.85. A large, sustained negative loop voltage during the steady-state portion of the discharge indicates that a substantial noninductive component of Ip exists in these plasmas. Transport code analysis indicates that the bootstrap current constitutes up to 65% of Ip. Magnetohydrodynamic (MHD) ballooning stability analysis shows that, while these plasmas are near, or at the βp limit, the pressure gradient in the plasma core is in the first region of stability to high-n modes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859647
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  • 10
    Digitale Medien
    Digitale Medien
    Investigation of global Alfvén instabilities in the Tokamak Fusion Test Reactor (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2122-2126 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Toroidal Alfvén eigenmodes (TAE) were excited by the energetic neutral beam ions tangentially injected into plasmas at low magnetic field in the Tokamak Fusion Test Reactor (TFTR) [Proceedings of the 11th International Conference on Plasma Physics and Controlled Fusion Research (IAEA, Vienna, 1987), Vol. 1, p. 51]. The injection velocities were comparable to the Alfvén speed. The modes were identified by measurements from Mirnov coils and beam emission spectroscopy (BES). TAE modes appear in bursts whose repetition rate increases with beam power. The neutron emission rate exhibits sawtoothlike behavior and the crashes always coincide with TAE bursts. This indicates ejection of fast ions from the plasma until these modes are stabilized. The dynamics of growth and stabilization were investigated at various plasma currents and magnetic fields. The results indicate that the instability can effectively clamp the number of energetic ions in the plasmas. The observed instability threshold is discussed in light of recent theories. In addition to these TAE modes, intermittent oscillations at three times the fundamental TAE frequency were observed by Mirnov coils, but no corresponding signal was found in BES. It appears that these high-frequency oscillations do not have a direct effect on the plasma neutron source strength.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.860462
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