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  • 1
    Digitale Medien
    Digitale Medien
    A 1-V series-array Josephson voltage standard operated at 35 GHz (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4700-4702 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Josephson voltage standards utilize microwave-induced constant voltage steps in the dc characteristic of Josephson tunnel junctions. This paper describes the design and operation of array circuits with 108 and 2000 junctions connected in series. In contrast with similar realizations, simple Q-band equipment is used for the microwave supply. The microwave attenuation of 1000 junctions was about 1 dB. The version with 2000 junctions generated Josephson voltages up to 1.2 V when operated at 35 GHz. The stability times of the quantized levels were, under normal laboratory conditions (unshielded room), better than 10 min.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346149
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  • 2
    Digitale Medien
    Digitale Medien
    Development testing of the U.S. common long pulse source at 120 kV (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2357-2365 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The U. S. magnetic fusion energy program has developed a single design, long-pulse neutral beam source for TFTR, MFTF-B, and DIII-D. The arc is a very compact axial magnetic line cusp. The accelerator is an actively cooled tetrode with water-cooled grid tubes of shaped molybdenum forming "slot'' beamlets. DIII-D and MFTF-B configurations have an 80-kV accelerator gap, with a 12×18 cm aperture, and a 10-m "module'' focus. TFTR modules are unfocused, with a 120-kV gap and 12×43-cm mask. The first CLPS was tested in the TFTR configuration, at 120 kV, 2s. Optimum current was 73 A, or 1.76 μpervs (deuterium), with 80%–85% atomic fraction. Optimum divergence of ions plus neutrals was 0.4° parallel to the slots, and 0.7° perpendicular to the slots (1/e half-angle). The combination of an axial cusp magnetic bucket and slot accelerator apertures gives the common long pulse source about twice the beam power per unit cross section of other long pulse sources, plus lower divergence in the direction parallel to the slots.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1139961
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  • 3
    Digitale Medien
    Digitale Medien
    Pellet injection on the ZT-40M reversed field pinch (1987)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 1401-1405 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The four barrel pneumatic pellet injector originally used on the Alcator C tokamak at MIT has been reconfigured for use on the ZT-40M reversed field pinch (RFP) at Los Alamos National Laboratory. The lower temperature and density in this device require operation at velocities significantly lower than on Alcator. Allowing a 2-s warmup prior to firing the injector has enabled operation with pressures as low as 40 psig and velocities ranging as low as 200 m/s with H2 pellets, without major cryostat modification. Initial injection experiments in the ZT-40M plasma have verified that pellet refueling is effective for density control, but the net particle inventory increase is less than might be expected based on simple models. Indications of nonoptimal penetration and curvature of the pellet trajectory, in addition to comparable time scales for particle confinement and pellet transit, may account for this.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1139421
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  • 4
    Digitale Medien
    Digitale Medien
    Energetic electron measurements in the edge of a reversed-field pinch (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 143-159 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The edge plasma of the ZT-40M [Fusion Technol. 8, 1571 (1985)] reversed-field pinch has been studied using a combination of three different plasma probes: a double-swept Langmuir probe, an electrostatic energy analyzer, and a calorimeter–Langmuir probe. The edge plasma has been measured both with and without a movable graphite tile limiter present nearby in the plasma. Without a limiter a fast nonthermal tail of electrons (T(approximately-equal-to)350 eV) is detected in the edge plasma with nearly unidirectional flow along B and having a density between 2% and 10% of the cold edge plasma (T(approximately-equal-to)20 eV). The toroidal sense of this fast electron flow is against the force of the applied electric field. A large power flux along B is measured flowing in the same direction as the fast electrons and is apparently carried by the fast electrons. With the limiter present the fast electrons are still detected in the plasma, but are strongly attenuated in the shadow of the limiter. The measured scrape-off lengths for both the fast electrons and the cold plasma indicate cross-field transport at the rate of, or less than, Bohm diffusion. Estimates indicate that the fast electrons could carry the reversed-field pinch current density at the edge and, from the measured transverse diffusion rates, could also account for the electron energy loss channel in ZT-40 M. The long mean-free-path kinetic nature of these fast electrons suggests that a kinetic process, rather than a magnetohydrodynamic process that is based upon a local Ohm's law formulation, is responsible for their generation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859526
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  • 5
    Digitale Medien
    Digitale Medien
    Asymmetric magnetic flux generation, m=1 activity, and edge phenomena on a reversed-field pinch (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 1828-1838 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The ZT-40M [Fusion Tech. 8, 1571 (1985)] reversed-field pinch has been used to study magnetic flux perturbations during high-θ [θ=Bθ(a)/〈Bφ〉〉1.6] discharges. Asymmetric toroidal magnetic flux perturbations are found to be associated with magnetic flux emerging through the toroidal shell gap and with m=0 magnetic disturbances moving toroidally. Ramping current discharges, which are a special case of high-θ operation, show the most robust self-generation of toroidal flux. The electron density fluctuations on the inside major radius and associated m=1 and m=0 fluctuations seen on edge magnetic field probes provide a clearer picture of activity during a soft x-ray sawtooth crash. During the sawtooth crash, significant magnetic energy is apparently converted into kinetic energy of the particles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.866198
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  • 6
    Digitale Medien
    Digitale Medien
    Spectroscopic investigation of a reversed field pinch operated without limiters (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 3136-3141 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Spectroscopic measurements on the ZT-40M reversed field pinch [submitted to Fusion Tech.] discharge are reported. Specifically, the impurity content, Zeff, recycling behavior, ion temperature, and propagation of magnetohydrodynamic modes in the edge are addressed. The importance of the plasma–wall interaction in ZT-40M, operated without limiters, is demonstrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.865355
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  • 7
    Digitale Medien
    Digitale Medien
    A comparison of edge turbulence in tokamaks, stellarators, and reversed-field pinches* (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2491-2497 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Edge equilibrium, turbulence and transport related plasma parameters from the Advanced Toroidal Facility (ATF) [Fusion Technol. 10, 179 (1986)] torsatron, the ZT-40M [Fusion Technol. 8, 1571 (1985)] reversed-field pinch, the Phaedrus-T [Nucl. Fusion 32, 2040 (1992)] tokamak, the Texas Experimental Tokamak (TEXT) [Nucl. Technol. Fusion 1, 479 (1981)], and the Tokamak Fusion Test Reactor (TFTR) [in Plasma Physics and Controlled Nuclear Fusion Research, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, p. 9] have been obtained using a standardized Langmuir probe array and a consistent set of data analysis packages. Additional data from some other devices have also been furnished via private communications and incorporated from published results. Experimental results over a wide range of parameters are compared and the turbulence contribution to edge transport are assessed. Certain physical properties that are relevant to the modeling of edge turbulence are identified: namely, shear decorrelation of turbulence, the role of resistive dissipation and electron parallel thermal conduction, radial mode structure in sheared magnetic field, and electromagnetic contribution to the parallel Ohm's law.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.860734
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  • 8
    Digitale Medien
    Digitale Medien
    Effects of limiters on reversed-field pinch confinement (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1701-1707 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: This paper documents the effects on confinement of introducing discrete limiters into the edge plasma of the ZT-40M reversed-field pinch (RFP) [Fusion Technol. 8, 1571 (1985)]. RFP confinement is not significantly degraded by appropriately designed single limiters inserted to a sufficient depth for effective local vacuum vessel wall protection. Inserting limiters too deeply into the plasma results in excess limiter heating, and a consequent increase in the impurity content of the plasma. Under these conditions the plasma loop voltage increases. The heating of the limiters is observed to be asymmetric, with the majority of the heat flux in ZT-40M being attributable to suprathermal electrons [Tsupra∼2–3×Te(0)] reaching the edge moving almost unidirectionally along magnetic-field lines.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859689
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  • 9
    Digitale Medien
    Digitale Medien
    Oscillating field current drive experiments in a reversed field pinch (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 2285-2291 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Steady-state current sustainment by oscillating field current drive (OFCD) utilizes a technique in which the toroidal and poloidal magnetic fields at the plasma surface are modulated at audio frequencies in quadrature. Experiments on the ZT-40M reversed field pinch [Fusion Technol. 8, 1571 (1985)] have examined OFCD over a range of modulation amplitude, frequency, and phase. For all cases examined, the magnitude of the plasma current is dependent on the phase of the modulations as predicted by theory. However, evidence of current drive has only been observed at relatively low levels of injected power. For larger modulation amplitudes, the data suggest that substantial current drive is offset by increased plasma resistance as a result of modulation enhanced plasma–wall interactions. The initial experimental results and supporting theoretical interpretations of OFCD are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.866629
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  • 10
    Digitale Medien
    Digitale Medien
    Application of optical phase conjugation to plasma diagnostics (invited) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 953-957 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Several possibilities for plasma diagnostics provided by optical phase conjugation and, in particular, self-pumped phase conjugation in barium titanate (BaTiO3) are discussed. These include placing a plasma within a dye laser cavity equipped with a phase conjugate mirror for intracavity absorption measurements, time differential refractometry with high spatial resolution, and simplified real-time holographic interferometry. The principles of phase conjugation with particular reference to photorefractive media and the special advantages of self-pumped phase conjugation are reviewed prior to the discussion of the applications. Distinctions are made in the applications between those for which photorefractive conjugators are essential and those for which they only offer experimental simplification relative to other types of phase conjugators.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1138058
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