First results of radial array experiments in microsecond regime

Summary form only given. The Sphinx machine1 has been used to implode cylindrical Z- pinches to produce k-shell emission from Aluminum wire arrays and Argon gas puffs. Despite the long implosion time of Sphinx driver, efficient plasma radiation sources were obtained especially with the use of multi microsecond prepulse technique for wire array loads4. However, the interest of such k-shell emitter is reduced due to the dimension of the return current can that does not allow to work close to the source. Therefore, Centre d'Etudes de Gramat has started to look at the possibility of getting efficient plasma radiation sources with different initial geometries. Nice results were recently obtained on Magpie3 with radial array loads. In that configuration, wires are radially connecting two concentric electrodes and higher ablation rate close to the cathode generates a magnetic cavity that implodes axially and radially. Then accretion of mass on the axis generates a small z-pinch source. We present here results of preliminary experiments done on a small test bed (730 kA, 1.2 I¿¿s) that was built to study radial wire array loads behavior with longer current rise time than on Magpie. Experimental results of radial wire array and radial array focus loads of typical dimensions 70 mm diameter for the anode and between 6 and 50 mm for the cathode are given. Comparison of the two schemes is proposed and the main parameters used to describe the dynamics of the implosion such as the ablation rate, ablation velocity and the time of the end of the ablation are experimentally determined4. We show that the ablated fraction near the cathode may be less than the classical value of 50% used for cylindrical wire arrays. Numerical simulations using the 3D MHD Gorgon code are shown.