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1

Digitale Medien

Novel gas-doping technique for local spectroscopic measurements in pulsed-power systems (1998)

Arad, R. ; Ding, L. ; Maron, Y.

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

Review of Scientific Instruments 69 (1998), S. 1529-1533

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: A novel method for doping plasmas in pulsed-power experiments with gaseous elements has been developed. A fast gas valve, a nozzle, and a skimmer are used to generate an ultrasonic gas beam that is injected into a planar-geometry microsecond plasma-opening switch (POS). An array of ionization probes with relatively high spatial and temporal resolutions was developed for diagnosing the absolute injected-gas density and its spatial profile. The properties of the gas column were also studied using spectroscopy of line emission that results from the interaction of the doped gas with the POS prefilled plasma. The doped column is found to have a width of (approximate)1 cm and a density of (0.8–1.7)×1014 cm−3. Observations of characteristic emission lines from the doped atoms and their ions allow for various spectroscopic measurements, such as the magnetic field from Zeeman splitting and the ion velocity distributions from Doppler shifts, that are local in three dimensions. It is shown that this gas doping technique can also be used to study proton-dominated plasmas that cannot be studied with simple emission spectroscopy due to the lack of light emitting ions. The variety of gases used with this method, together with the small valve dimensions and its fast opening, make it potentially useful for broad diagnostics of various short-duration plasma experiments. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1148791

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2

Digitale Medien

Spectroscopic determination of the magnetic-field distribution in an imploding plasma (1998)

Davara, G. ; Gregorian, L. ; Kroupp, E. ; [weitere]

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

Physics of Plasmas 5 (1998), S. 1068-1075

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The time-dependent radial distribution of the magnetic field in a high density z-pinch plasma has been determined by observation of the contribution of the Zeeman effect to the spectral profiles of ionic emission lines. The dominance of the line profiles by the Stark broadening required high-accuracy profile measurements and the use of polarization spectroscopy. The plasma implodes in (similar, equals)600 ns, and the field distribution was measured up to 90 ns before stagnation on axis. During the implosion the plasma was found to conduct the entire circuit current. By comparing the data to the solution of the magnetic diffusion equation the electrical conductivity of the plasma was determined, found to be in agreement with the Spitzer value. These measurements, together with our previously measured ion velocity distributions, allowed for the determination of the time-dependent relative contributions of the magnetic and thermal pressure to the ion radial acceleration across the plasma shell. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.872637

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3

Digitale Medien

Observations of two-dimensional magnetic field evolution in a plasma opening switch (1998)

Shpitalnik, R. ; Weingarten, A. ; Gomberoff, K. ; [weitere]

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

Physics of Plasmas 5 (1998), S. 792-798

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The time dependent magnetic field distribution was studied in a coaxial 100-ns positive-polarity Plasma Opening Switch (POS) by observing the Zeeman effect in ionic line emission. Measurements local in three dimensions are obtained by doping the plasma using laser evaporation techniques. Fast magnetic field penetration with a relatively sharp magnetic field front (≤1 cm) is observed at the early stages of the pulse (t(approximately-less-than)25). Later in the pulse, the magnetic field is observed at the load-side edge of the plasma, leaving "islands" of low magnetic field at the plasma center that last for about 10 ns. The two-dimensional (2-D) structure of the magnetic field in the r,z plane is compared to the results of an analytical model based on electron-magneto-hydrodynamics, that utilizes the measured 2-D plasma density distribution and assumes fast magnetic field penetration along both POS electrodes. The model results provide quantitative explanation for the magnetic field evolution observed. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.872766

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4

Digitale Medien

Spectroscopic investigations of the plasma behavior in a plasma opening switch experiment (1995)

Sarfaty, M. ; Maron, Y. ; Krasik, Ya. E. ; [weitere]

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

Physics of Plasmas 2 (1995), S. 2122-2137

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The electron density, the electron kinetic energy, the particle motion, and electric fields in a coaxial positive-polarity plasma opening switch (POS) were studied using spectroscopic diagnostics. A gaseous source that injects the plasma radially outward from inside the inner POS electrode was developed. The plasma was locally seeded with various species, desired for the various measurements allowing for axial, radial, and azimuthal resolutions both prior to and during the 180 ns long current pulse. The electron density was determined from particle ionization times and the electron energy from line intensities and time dependent collisional-radiative calculations. Fluctuating electric fields were studied from Stark broadening. The ion velocity distributions were obtained from emission-line Doppler broadenings and shifts. The early ion motion, the relatively low ion velocities and the nearly linear velocity dependence on the ion charge-to-mass ratio, leads to the conclusion that the magnetic field penetrates the plasma early in the pulse. The ion velocity dependence on the axial location were thus used to infer the time dependent axial distribution of the magnetic field, indicating the formation of a relatively high current density at the load-side edge of the plasma. This is expected to cause plasma acceleration towards the load, found to be supported by charge-collector measurements. The fast magnetic field penetration could be explained by mechanisms based on the Hall effect. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.871299

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5

Digitale Medien

Spectroscopic investigation of fast (ns) magnetic field penetration in a plasma (1995)

Sarfaty, M. ; Shpitalnik, R. ; Arad, R. ; [weitere]

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

Physics of Plasmas 2 (1995), S. 2583-2589

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The time-dependent magnetic field spatial distribution in a coaxial positive-polarity plasma opening switch (POS) carrying a current (approximately-equal-to)135 kA during (approximately-equal-to)100 ns, was investigated by two methods. In the first, ionic line emission was observed simultaneously for two polarizations to yield the Doppler and Zeeman contributions to the line profiles. In the second method, the axial velocity distribution of ions was determined, giving the magnetic field through the ion equation of motion. This method requires knowledge of the electron density, here obtained from the observed particle ionization times. To this end, a lower bound for the electron kinetic energy was determined using various line intensities and time-dependent collisional-radiative calculations. An important necessity for POS studies is the locality of all measurements in r, z, and θ. This was achieved by using laser evaporation to seed the plasma nonperturbingly with the species desired for the various measurements. The Zeeman splitting and the ion motion showed magnetic field penetration through the 3.5 cm long plasma at a velocity (approximately-equal-to)108 cm/s. The current density was found to be relatively high at the load-side edge of the switch plasma. It is suggested that this may cause plasma acceleration into the vacuum section toward the load, which is supported by charge-collector measurements. The fast magnetic field penetration agrees with estimates based on the Hall-field mechanism. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.871220

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