Laser initiated hollow gas-embedded Z-pinch

A preliminary study of a shell gas-embedded Z-pinch initiated by a 8 ns Nd-YAG laser pulse (1.06 µm) is presented. The experiment was carried out on a pulsed power generator (GEPOPU) capable of delivering a peak current of 200 kA with a rise time of 35 ns, 120 ns pulse length. The experiments reported here were carried out in Hydrogen gas at 1/3 atm. Flat electrodes were used with a 10 mm separation, with a 3 mm central hole at the anode to allow the passage of the preionizing laser. The laser was focussed onto the cathode, creating a circular metallic plasma from which an annular preionization is established after the discharge voltage is applied. Different optical configurations were used to obtain an annular focal spot were tested, the results shown here were obtained using a diverging lens with its central part blocked off in combination with a converging lens. The second harmonic of the Nd-YAG laser used to preionize the plasma was used to do the optical diagnostics. A compression from 1.5 to .5 mm of the resulting plasma is observed, no instabilities are observed during the compression phase. Further work is planned to study the stability properties of the discharge after peak compression.