Laser probing experiments with X-pinches

Summary form only given. For investigating the internal structure of the neck, the position of the neck in the relation to the cross-point of the X-pinch wires, the neck structure during pinching, plasma parameters in the vicinity of the neck and in the plasma around of the wire´s core were studying using pulsed lasers. For solving this problem we used shadowgraphy and interferometry. For the plasma probing we used a second harmonic of Nd laser with /spl sim/7 nsec pulse duration and /spl sim/50 mJ energy. Accuracy of synchronization current was /spl plusmn/5 ns. Spatial resolution was /spl sim/15 /spl mu/m. An X-pinch is formed by placing two fine (20-50 /spl mu/m) wires between the output electrodes of a high current pulser so that the wires cross and touch in mid-gap. The parameters of installation were: maximum current /spl sim/300 kA, voltage /spl sim/50 kV, pulse duration /spl sim/100 ns. The axial displacement of the position of the neck from cross-point of the wire on value /spl sim/50 /spl mu/m was recorded. Reconstruction of the electron density in the transparent region of the neck gives value /spl sim/1.6/spl times/10/sup 20/ cm/sup -3/ at a distance of /spl sim/50 /spl mu/m from axis. Behavior of the interference lines shows that two different regions in X-pinches exist.