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1

Digitale Medien

Effect of space-charge limited emission on measurements of plasma potential using emissive probes (2000)

Ye, M. Y. ; Takamura, S.

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 7 (2000), S. 3457-3463

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Effects of space-charge limitation have been considered for an analytical estimation of plasma potential with use of emissive probes, taking account of a correct expression of emission current under space-charge limited condition. The analytical results are obtained for the floating potential method of emissive probe and for the differential emissive probe method, both without and with an oscillating ac potential. In the case of the floating potential method, the operating condition is discussed for different plasma parameters at several probe temperatures. These results indicate that the floating potential of the emissive probe gives us the plasma potential to an accuracy of the order of the plasma electron temperature Te/e for a strong probe emission. In the case of the differential emissive probe method, the relations among space-charge effects, the ratio of thermoelectron emission current to plasma electron collection current, the plasma electron temperature, the probe temperature, and the amplitude of the oscillating ac potential are discussed in terms of determination of plasma potential. In addition, the analytical results also indicate that the midpoint of the two peaks in the derivative d〈Iem〉/dV curve is a good method for measuring the time-averaged plasma potential. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.874210

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2

Digitale Medien

Nonlinear interactions between high heat flux plasma and electron-emissive hot material surface (1996)

Ye, M. Y. ; Masuzaki, S. ; Shiraishi, K. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 3 (1996), S. 281-292

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Nonlinear dynamic behaviors are investigated for a system composed of high heat flux plasma and electron-emissive hot material surface. Phase transitions due to bifurcation have been observed in the experiments and analyzed numerically by using a series of simple equations describing energy balance as well as sheath formation, including a new Child–Langmuir expression for an electron emission from the material surface into the plasma. It is found that the thermal insulation between these two constituent parts depends not only on plasma parameters but also strongly on electron-emission characteristics of the material surface in a nonlinear way. The electron emission leads to a strong reduction of sheath voltage and a large enhancement of heat flux density on the material surface. The plasma is cooled when it is in contact with a strongly electron-emissive material surface. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.871854

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3

Digitale Medien

Heat flows through plasma sheaths : The 39th annual meeting of division of plasma physics of APS (1998)

Takamura, S. ; Ye, M. Y. ; Kuwabara, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 5 (1998), S. 2151-2158

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Plasma heat flow to material surfaces through sheaths is studied, taking several key physics factors into account. Electron emission from the surface, which breaks a thermal insulation of the sheath, is studied in both thermoelectron emission (TEE) and secondary electron emission (SEE), in which a correct expression under space charge limited condition is given for arbitrary sheath voltages. Nonlinear thermal bifurcation induced by electron emission is analyzed in the experiment and the theory. The local heat flow was found to be enhanced by a thermal contraction induced by cross-field potential variation in a plasma. An enhancement of SEE of hydrogen-absorbed graphite, and a suppression of SEE by the gyromotion of emitted electrons in obliquely incident magnetic field are identified. The effects of ion reflection on the surface and ponderomotive force are also discussed in terms of energy transmission factor δ. An anomaly of δ in detached recombining plasmas is discussed. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.872888

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4

Digitale Medien

The crystal structure of the seramic superconductor of the Y−Ba−Cu−O compounds (1987)

Shu, J. F. ; Shen, J. C. ; Yao, K. L. ; [weitere]

Springer

The European physical journal 69 (1987), S. 29-31

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ISSN: 1434-6036

Quelle: Springer Online Journal Archives 1860-2000

Thema: Physik

Notizen: Abstract The crystal structure of one phase of superconductor Y−Ba−Cu−O Compound is analysed by RASA-5RP Four-circle single crystal diffractometer. It is found that the crystal is tetragonal with parametersa=3.8614 Å,b=3.8614 Å,C=11.6803 Å. In the crystal structure Ba situates at the Wyckoff (0, 0, 0.3094) position, Y at the special position (0, 0, 0), Cu ions occupy another special position (0.5, 0.5, 0.5) and the Wyckoff position (0.5, 0.5, 0.1391) with some substitution by Y and some Oxygen vacancies surrounding Cu and Y.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01560606

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