Comparison Between Laser Initiated Hollow Gas Embedded Z‐pinches with Different Initial Radius

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 1018 cm−3 were measured in both cases. Temperature estimates using Bennett relation are of 18...