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  • 11
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 1263-1267 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Tokamaks require toroidal loop voltage for breakdown of the neutral gas, current rise, and the flat top phase. The temporal profile of the loop voltage established by the change of flux linked by the ohmic transformer has to be a noncosine waveform. In this paper a multistage capacitor bank is described which was used to energize the ohmic transformer in tokamak ADITYA with a major radius of 0.75 m, minor radius of 0.25 m, and a toroidal field of 1.5 T at the plasma center. A combination of capacitors charged to different voltages are switched in at appropriate times, to realize an experimental demand for initial high loop voltage followed by a lower sustaining loop voltage. Theoretical prediction for the duration of the secondary loop voltage as a function of circuit parameters, for a fast bank operation of 6 kV, slow bank, 4–4.5 kV, and slow bank, 2–2.5 kV yield t0=1.25 mS, t1=4.95 mS, and t2=24.1 mS. These values are in close agreement to the measured values of t0=1.39 mS, t1=5.7 mS, and t2=23.7 mS. The trigger delays to the various capacitor bank sections are parameter dependent. To avoid repetitive adjustments in the delays, a novel scheme for consistent triggering is also highlighted.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3127-3135 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The use of controlled-clearance piston gauges as highly accurate primary pressure standards is well established. However, the operation of a controlled-clearance gauge is more complicated than that of the familiar simple or reentrant designs. An investigation has been performed on a modified design of a piston gauge for which the same piston/cylinder can be operated in either the controlled-clearance, simple, or reentrant modes, to determine the degree of degradation in accuracy of measured pressure using the gauge in either the simple or reentrant modes as a standard. How the particular characterization of the standard gauge affects the calibration parameters of a test gauge is also explored. The effective areas of the test gauge are within 4.5 parts per million (ppm) when the standard is used in the simple mode instead of the controlled-clearance mode, up to a pressure of 28 MPa, whereas in the case of the reentrant mode this deviation increases from 2.5 ppm at 7 MPa to 14 ppm at 26 MPa.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1466-1468 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A multigap pseudospark device filled with hydrogen or argon gas is operated up to 20 kV and ejected ion beam characteristics are experimentally investigated. The ion beam of peak current density in excess of ∼500 A/cm2 and pulse duration ∼50 ns is extracted at repetitive frequency of several tens of Hz. Results of the scaling study for the ion beam current with breakdown voltage, external capacitance, and number of insulator gaps are presented.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3093-3095 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An experimental investigation of the effect of magnetic field on the breakdown voltage characteristics of a multigap pseudospark device, with hydrogen gas, in a hollow anode–cathode, as well as a hollow cathode–anode configuration, is presented. The breakdown pressure at a particular discharge voltage increases with the increase in the applied axial magnetic field, and the magnitude of the increase is more pronounced at lower discharge voltages causing a right shift to the characteristic discharge curve in both the configurations. Application of a transverse magnetic field also resulted in a shift of the characteristic discharge curve towards the right. The observed results are compared and discussed with that found for parallel electrode geometry. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 2643-2651 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A toroidal equilibrium of a reversed field pinch based on Taylor's Bessel function model (BFM) is investigated. Characteristics of the toroidal relaxed state for a few reversed field pinch devices are presented in detail. It is shown that the toroidal relaxed state agrees with experimental observations not only in the inner region, like BFM, but also to a good extent in the outer region of a reversed field pinch. Inclusion of toroidal effects in the BFM leads to a decrease of the toroidal reversed flux and an increase of the minor radius at which the toroidal field reverses. The toroidal relaxed state has "μ'' decreasing in the outer region when calculated using experimental procedure and a saturation of the on-axis value of the pinch parameter aitch-theta. Toroidal effects and finite plasma pressure lead to enhancement of the pinch parameter aitch-theta. The results in this paper show that the observed departure of experiment from the BFM is partly due to the toroidal geometry.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 3445-3450 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A closed field-reversed configuration has been produced by a long pulse duration (≈ 500 nsec) intense electron beam injected into hydrogen gas. The field reversal is created by the beam current during the duration of beam propagation, but is sustained by the beam-induced plasma currents after the exit of the beam. Reconnection of the antiparallel field lines has been observed, which results in formation of a prolate spheroid. The axial extent of the spheroid is 80.0 cm. It contracts immediately after its formation with the supersonic velocity. Attempts were made to close axial currents along the closed poloidal field lines.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 55 (2000), S. 0 
    ISSN: 1365-2044
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 371-375 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Tungsten-doped YBa2Cu3O7−x superconducting samples are characterized with the help of resistivity, crystal structural, microstructural, density d, and critical current density Jc studies for doping concentrations varying from 0.00 to 0.14 mol % of WO3. It has been found that doping of WO3 has hardly any influence of Tc, whereas it seems that d and Jc are affected. d and Jc of the samples increase in the range 0〈WO3≤0.04, but above this range, both start decreasing. The maximum Jc obtained at 77 K and zero magnetic field in YBa2Cu3O7−x doped with 0.04 mol % of WO3 is 450 A/cm2. The lower concentrations (〈0.04 mol %) seem to improve the density, whereas higher concentrations lead to porous structure and also induce the formation of BaCuO2 and Y2Ba1Cu1O5 nonsuperconducting phase as revealed by scanning electron microscopy, energy dispersive spectral, and x-ray diffraction analyses. The x-ray diffraction analysis also showed no appreciable change in the lattice parameters with WO3 doping. It appears that the WO3 doping changes the microstructure of YBa2Cu3O7−x to influence its Jc.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5322-5326 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The dynamic behavior of continuous wave (cw) laser-induced crystallization in the a-Si:H film on a quartz substrate is studied by light scattering. Microcrystals of dimensions less than 30 A(ring) could be grown in a stable state and it is demonstrated that the surface-to-volume correction is essential for estimating the frequency of the crystallinelike mode. It is suggested that bulk-induced crystallization may be responsible for the formation of very small crystallites.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 2487-2491 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A high-brightness electron beam produced by a six-gap pseudospark chamber operated in 5–25 kV voltage and 30–70 mTorr pressure ranges is experimentally investigated. The electron beam of current 150 A at an average energy of 20 keV and pulse duration of 10 nsec is extracted with a repetitive frequency of ∼10 Hz. The electron-beam current scales linearly with the breakdown voltage and about 20% of the stored energy is converted into the total beam energy. The time-integrated rms emittance of the electron beam is measured, and a typical value is found to be 65 mm mrad, yielding a normalized brightness of the beam Bn≈2×1010 A/(m2 rad2).
    Materialart: Digitale Medien
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