[en] An interferometric method for measuring the displacement of diffuse surfaces moving with velocities of a few microsecond is presented. The method utilizes the interference between two light beams reflected from a constant area of the moving surface at two different angles. It enables the detection of high rate velocity variations. Light source of a fairly low temporal coherence and power around 100mW is needed. (author)

[en] An interferometric technique for measuring displacements of surfaces moving at velocities in the range of a few millimeters per microsecond is presented. The Doppler shift of frequency of light scattered from such surfaces is too high to be detectable by known devices. The present technique is based upon monitoring the signal resulting from the interference between two beams reflected from the surface at different incidence angles. Measurement systems for specularly as well as diffusely reflecting surfaces are described. Light source with very modest temporal coherence delivering about 100 mw power is required. The accuracy of the technique is discussed. (author)

[en] Excited C++ and Al++ ions produced in the surface flashover plasma in a magnetically insulated diode have been used to measure the electric field and ion transverse velocities in the acceleration gap by spectroscopic techniques. The emission lines of ions traversing the gap are Stark shifted from their natural wavelength because of the diode electric field; this allows a determination of the electric field as a function of distance across the gap by appropriate choice of an ion line to observe. If the light is viewed transverse to the acceleration direction, the width of lines which are not Stark shifted will be mostly determined by Doppler broadening due to the ion transverse velocities. The authors use the OMNI II generator (up to 500kV, 25kA, 80 nsec), with a planar diode, an insulating field of 5-10 kG and an A-K gap spacing of 6-9 mm. Surface flashover on a sheet of polyethylene covering the anode is the source of the anode plasma and provides a source for the C++ ions

[en] Spectroscopic methods have been developed to determine the electric field distribution and the plasma properties in pulsed power systems. This investigation was motivated by the suggestion that the electric field distribution across the acceleration gap of intense ion diodes can be measured by observing the Stark shift of spontaneous line emission or the laser-induced fluorescence of ions traversing the gap. The measurements show that electrons drifting in the diode gap spread beyond the theoretical electron-sheath region. These results, together with the measured distance between the field-excluding plasmas, are used in theoretical analyses of electron diffusion and diode impedance

[en] We describe a self-consistent statistical approach to account for plasma density effects in collisional-radiative kinetics. The approach is based on the characterization of three distinct types of electron states, namely, bound, collectivized, and free, and on the formalism of the effective statistical weights (ESW) of the bound states. The present approach accounts for individual and collective effects of the surrounding electrons and ions on atomic (ionic) electron states. High-accuracy expressions for the ESWs of bound states have been derived. The notions of ionization stage population, free electron density, and rate coefficient are redefined in accordance with the present characterization scheme. The modified expressions for the probabilities of electron-impact induced transitions as well as spontaneous and induced radiative transitions are then obtained. The influence of collectivized states on a dense plasma ionization composition is demonstrated to be strong. Examples of calculated ESWs and populations of ionic quantum states for steady state and transient plasmas are given

[en] Abstract only

[en] Excited ions, produced in the surface-flashover plasma in a magnetically insulated diode, spontaneously emit light from the anode plasma region as well as (if the life time of the excited level is at least a few ns) from the diode acceleration gap. The emission lines of the ions traversing the gap are shifted from their natural wavelength because of the Stark effect due to the diode electric field. If the light is viewed transverse to the acceleration direction, the line width will be mostly determined by Doppler broadening due to ion transverse velocities. The authors use the OMNI II diode (up to 500 kV, 25 kA, 80 ns) with an insulating B field of ≅12 kG and an A-K gap of ≅7mm. The light emission from the entire 6.5 x 12 cm area in front of the anode is viewed parallel to the applied B field. A spectral resolution of 0.5 A is obtained by dispersing the light using a spectrometer followed by 6 optical fibers attached to PM-tubes. Each channel output is calibrated in situ. The spatial resolution across the gap could be made as small as 0.3 mm and the temporal resolution was varied between a few to a few tens of ns. The line spectral profile is obtained at a single discharge for a given distance from the anode surface

[en] Local electron flux to the anode of a magnetically insulated diode is monitored. Intense electron burst to the anode and slow variations in the electron flux are observed. Unlike the slow signals the bursts are accompanied by sharp increases in microwave emission and by increases in the ion current density. The electron bursts are not affected by the presence of the anode plasma. Indications suggest that the bursts are initiated by processes in the cathode plasma

[en] Measurements of divergence of ion beams extracted from ion diodes using tiny holes yield ambiguous information since at each instant of time ions from different areas of the anode may be observed. Streak photographs of ion beamlets which passed through such holes do not provide unambiguous information as to the source of the observed ion deflections since these can be affected within the diode by time dependent magnetic fields, and cathode and anode phenomena, as well as by space charge fields outside the diode. Here ion beam deflections were observed by extracting a portion of an ion beam through a 1.4 cm diam aperture. Then the ions hit a scintillator which was photographed with a streak camera, allowing us to observe ions from a specific area (about 2 cm²) of the anode throughout the diode pulse. We also monitored the electron flux to the same anode region with two collimated x-ray detectors which helped to associate ion deflections with sources inside the diode. A thorough analysis of the data was used to infer the presence of perturbations in the diode potential surfaces which have specific characteristics. In the paper of Maron et al. an explanation of the observations in terms of different electrostatic potential perturbations is presented. In this paper, we present the complete data analysis which led to these explanations. Observations show that ion deflections are too large (up to 20⁰) to be explained by local magnetic effects. Different classes of data will be shown that imply different shaped perturbations in the equipotentials. Finally, we will show data which implies that the perturbation transverse scale length was one to a few cm (gap spacing is <1 cm). These experiments were performed using the LONGSHOT magnetically insulated diode, an annular, 100 kV, long pulse (about 600 ns) system having a radial magnetic insulation field

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