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The MHD mode trajectory in the Madison Symmetric Torus reversed-field pinch has been found to obey the sine-Gordon equation. Corresponding to experiment, a perturbation analysis predicts the locations of mode locking to be at the vacuum chamber poloidal and/or toroidal gaps. The mode's energy dissipates when it locks, as shown by a decaying spiral phase-plane trajectory. Unlocked modes travel around the torus without an abrupt energy loss. By varying key machine parameters obtained by statistical analysis, the probability of locking in accordance with the experimental results can be predicted. 相似文献
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Hoffman D. J. Shohet J. L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1978,6(4):449-453
A magnetic mirror (mirror ratio 2.38:1) containing ECRH generated hydrogen plasma, with a density of 5 x 1010 cm-3 with cold electron temperature of 11 eV, was used to study propagation of an artificially launched wave varying as ej(?t + m? - kz) at approximately the ion cyclotron frequency. The wave was transmitted between two similar internally placed helically wound antennas separated by 11 wavelengths. The coupling between them was enhanced by as much as 50 times in the presence of plasma. The m = 1 left-handed component was cut off when ? > ?ci. Electron temperatures could be increased by more than 2 times with the m = 1 mode, presumably due to ion heating. Little pump-out was observed. 相似文献
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Correlation of properties of common carbon fiber precursor materials, polyacrylonitrile (PAN) and pitch, with kinetics and sensitivity of microdisk electrodes, PAN T650, PAN HCB and Pitch P25, nanostructured by an electrochemical etching method was tested. Sensitivity of PAN electrodes is higher but kinetics are slower than at pitch electrodes due to more defects in PAN. Because of more surface oxides at PAN T650 adsorption of dopamine is greater than at PAN HCB electrodes but for uric acid adsorption is greater at PAN HCB. Uric acid sensitivity is related to high conductivity of PAN fibers, with an inverse relationship observed for dopamine. 相似文献
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K. A. Ashtiani J. L. Shohet F. S. B. Anderson D. T. Anderson J. B. Friedmann 《Plasma Chemistry and Plasma Processing》1992,12(2):161-175
The axial distribution of the electrostatic potentials ofan electron-cyclotron resonance (ECR) processing plasma confined in a do magnetic mirror geometry was characterized. The potential profiles far argon and helium at 8.0x 10–4 and 4.0 × 10–4 Torr were measured using electron emissive probes. The experimental measurements were then compared with the predictions of a one-dimensional, electrostatic, particle-in-cell computer code which runs on a personal computer. The potential profiles as predicted by the code showed good agreement with the experimental measurements. 相似文献
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J. L. Shohet 《The European physical journal. Special topics》2007,147(1):191-207
This paper presents a new nonlinear model which describes
localized magnetohydrodynamic (MHD) modes in reversed-field pinch
(RFP) experiments. To date, nearly all experimental and theoretical
work in this area has relied on the use of Fourier decomposition of
spatial variations as a function of time. Moreover, due to the
complexity of this nonlinear problem, previous work has been
restricted to the analysis of a relatively small number of modes. In
contrast, the model studied in this paper, based on the
damped-driven sine-Gordon (DDSG) equation, addresses the full
nonlinearity, does not rely on Fourier decomposition, and does not
require the range of the nonlinearity to be small. A specific
consequence of working with the full nonlinearity is the existence
of solitary waves in dispersive media. These solitary waves, a key
part of the model, are used to describe the so-called slinky
mode propagating in the plasma. A remarkable resemblance is seen
between the waveforms obtained from experiments and the mathematical
predictions of the new model. 相似文献
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Friedrich W. A. Shohet J. L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1976,4(4):296-297
Plasma heating at the lower hybrid resonance was studied experimentally in a canted magnetic mirror in order to determine the effects of magnetic field curvature on heating efficiency. Heating occurred mainly on what would be the "outside" of an equivalent torus, peaking near the hybrid resonant layer. The best conditions for heating were seen to be a relatively flat density profile of magnitude slightly below that where hybrid resonance would be expected. The density profile was seen to move "outward" as cant angle was increased, while the hybrid layers were seen to move oppositely, toward what would be the inside of the torus. No significant deleterious effects on the efficiency of the lower hybrid resonant heating (LHRH) were observed as the canting was changed. 相似文献
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Shohet J. L. Hamann J. R. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1975,3(3):179-181
Experiments were performed on an electron cyclotron resonance plasma in a dc magnetic mirror to determine the effects of lower hybrid resonance radiation on the anisotropy of the plasma. It was found that the anisotropy of the plasma hot electrons decreased, the flux of hot electrons escaping through the mirror throats decreased and the midplane wall bremsstrahlung rate slightly increased as lower hybrid resonance power was increased. This is explained by observing that cold plasma, expelled by the lower hybrid radiation, decreases the number of scattering centers in the midplane, which results in a deeper diamagnetic well for the hot electrons. 相似文献