Tesis Doctorado
Experimental observatións of pulsed capillary discharges
Autor
Wyndham, Edmund
Pontificia Universidad Católica de Chile
Institución
Resumen
In this thesis we present experimental results obtained with two configurations of a low stored energy fast capillary discharge. In one configuration a smooth, continuous capillary was used and in the other a novel segmented structure was studied.We implemented a refractive diagnostic to study fast dynamics in capillary discharges. It consists of a moiré-Schlieren deflectometry technique that provides a quantitative analysis ofthe refractive index gradients. The technique is composed of an angular deflection mapping system(moiré deflectometry) and a spatial Fourier filter (Schlieren). Temporal resolution of 12ps, 50 μm of spatial resolution and mínimum detectable gradient of (Vnc) min = 6x1018cm-4 were obtained. The diagnostic was implemented axially along the alumina tube of the continuous capillary of 1.6 mm inner diameter and 21 mm length. The detectable electron density for these conditions was 1x1017 cm-3.With this diagnostic we were able to observe for the first time the zippering effect in two different pressure gradients in the continuous capillary. We also could relate the spectral emission from filtered detector and time resolved spectra with the compression of the plasma due to the Lorentz force. Electron densities of the arder of (0.7-1)x1018 cm-3 were found at the timeof maximum emission in argon plasma and (2-4)x1017 cm-3 in xenon plasma (continuouscapillary configuration).We developed a scanning-monochromator system to obtain time resolved spectra. This system together with time integrated spectra provide important information about the emissionproperties of the plasma and also of the plasma dynamics. With this system, absolutemeasurement of emitted radiation energy from the plasma is possible. We obtained in thecontinuous configuration conversion efficiencies of 1.5% at 135A±1% and 3.6% at 110 A±2% when it is operated with xenon. These conversion efficiencies are the highest reported so far.In the segmented configuration we found that impurities are almost absent compared withthe smooth capillary. In this configuration we also found substantial differences in the time resolved argon spectra and in time integrated xenon spectra, compared with the smooth configuration.