Abstract

An experimental study of the effect of the initial radius on the formation of hollow gas embedded z-pinches is presented. These hollow pinches are formed using a ring precursor plasma generated by focussing a 10ns, 0.2J, 1064nm, Nd:YAG laser pulse onto the cathode surface. The laser pulse is focussed into a ring shape, by using a combination of a converging lens and an axicon. Ring radius variation give place to different initial radius of hollow z-pinches. The experiments were carried out on the Gepopu generator at 110kA, 50ns rise time using flat electrodes. The anode had a central hole, allowing the laser to be focussed onto the cathode surface. Experiments were performed in hydrogen at 1/3 of atmosphere. Schlieren and interferometry are the main plasma diagnostics using the second harmonic of the same laser. Comparison between initial radius of 2 and 3mm are presented, where electron densities on the order of 10 18 cm-3 were measured in both cases. Temperature estimates using Bennett relation are of 185 eV and 75 eV respectively. Pinch effect was observed for current density ∼ 5MA/cm2. © 2006 American Institute of Physics.