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[en] The quench behavior of Bi2Sr2CaCu2Ox (Bi2212) wire is investigated through numerical simulations. This work is part of the U.S. Very High Field Superconducting Magnet Collaboration (VHFSMC). Numerical simulations are carried out using a one-dimensional computational model of thermal transport in Bi2212 composite wires. A quench is simulated by introducing heat in a section of the wire, and the voltage and temperature are monitored as function of time and position. The quench energy, normal zone propagation velocity, and spatial distribution of temperature are calculated for varying transport current and applied magnetic field. The relevance of these simulations in defining criteria for experimental measurements is discussed.
[en] The pulse height weighting integration method for measuring H' (0.07) using a plastic scintillator has been developed through Monte Carlo simulations and laboratory tests. In order to design an optimal detector configuration, the parameters of input-window thickness and plastic scintillator thickness were investigated by EGS4 for their influences on the energy response for electrons. Based on the calculated deposited spectra in the plastic scintillator for electrons with various incident energies, a weighting function W(E), folded with the deposited energy spectra, was introduced in order to obtain a flat energy response in the low energy range. A constant response within ±3% was confirmed, by calculation, for electrons with energy >0.15 MeV. In addition, a preliminary experiment was performed using three beta sources (90Sr-90Y, 147Pm, 204Tl) and the energy response within ±6% for beta rays with the maximum energy >0.22 MeV was obtained. Some factors causing uncertainties in the measurements are also discussed in this article. (authors)
[en] The effect of differential divertor biasing on the outer/inner divertor asymmetry is investigated using a one-dimensional (1D) model in which the drift flow and ballooning-like transport are included. The simulation results show that (i) the outer/inner divertor asymmetries change with the applied divertor biasing, (ii) the change in divertor asymmetries induced by differential divertor biasing depends on the sign of the applied electric potential, (iii) the divertor asymmetries approach constant values with further increasing the positive divertor biasing or with decreasing the negative divertor biasing, (iv) differential divertor biasing can control the divertor asymmetry more effectively in the high recycling regime than in the low recycling regime. In addition, the effects of the E-vector x B-vector drift and ballooning-like transport on the variation in divertor asymmetry induced by differential divertor biasing are also discussed in this paper.
[en] A square lattice directed path confined to a wedge with vertex angle α exerts an entropic force Fα on the wedge. We show that this is a repulsive force of magnitude Fα = [(1 + cot2α)/(1 + cotα)2] log(cotα), if 0≤α<π/4 and Fα = 0, if π/4 ≤α≤π/2. This force is determined by examining the combinatorial properties of the directed path and by determining the exact entropic contribution to the free energy in the limit as the path length goes to infinite
[en] The origin of the two-peak photoemission and inverse-photoemission spectra in Ce and its pnictide compounds (CeP, CeSb, and CeN) is investigated with ab initio total-energy self-consistent supercell energy-band and molecular-cluster approaches to represent physically the competing mechanisms involved in d or f electron screening (antiscreening in the case of inverse photoemission) of the local 4f electron excitations. Good agreement with experiment is obtained in all cases including the ''anomalous'' case of CeN
[en] In this paper the Trichel pulse regime of corona discharge in airflows is numerically studied with a two-dimensional model. The model is based on the hydrodynamic drift–diffusion approximation, taking into consideration the flow of the air in the discharge gap. Both transverse and longitudinal airflows under different conditions have been investigated. The influences of airflows on the characteristics of the Trichel pulses were clearly observed and analysed. The simulation results proved to be compatible with experimental analysis reported in the literature. (paper)
[en] The criteria for merging shock waves formed by optical breakdowns on the surface of solids have been investigated. Targets made of different materials were successively irradiated by two CO2-laser pulses with energies up to 200 J and a duration of ∼1 μs. It is shown that the criteria under consideration can be applied to different targets and irradiation regimes and make it possible to calculate the parameters of repetitively pulsed laser radiation that are necessary to generate low-frequency sound and ultrasound in air.
[en] Kinetic effects of the toroidal rotation on the geodesic acoustic mode are theoretically investigated. It is found that when the toroidal rotation increases, the damping rate increases in the weak rotation regime due to the rotation enhancement of wave-particle interaction, and it decreases in the strong rotation regime due to the reduction of the number of resonant particles. Theoretical results are consistent with the behaviors of the geodesic acoustic mode recently observed in DIII-D and ASDEX-Upgrade. The kinetic damping effect of the rotation on the geodesic acoustic mode may shed light on the regulation of turbulence through the controlling the toroidal rotation
[en] Implanted-fluorine profiles in ITO films have been accurately measured using the 19F(p,αγ)16O resonance nuclear reaction at ER=872.1 keV, with width Γ=4.2 keV. A proper deconvolution calculation method was used to extract the true distribution of fluorine from the experimental excitation yield curves. The experimental range distribution parameters, Rp and ΔRp, were compared with those obtained from Monte Carlo simulation codes. (orig.)