First diagnostics of the z-pinch plasma target

The aim of the plasma target project is the investigation of the interaction of fast heavy ion beams with hot matter (1). For this beam-plasma experiment a plasma target was developed, that can be integrated into the beam line geometry of the UNILAC stripper region at GSI. The plasma is generated electrically in a z-pinch discharge, which is driven by a fast capacitor bank operating at pulsed powers in the GW-regime. Details of the z-pinch device are described elsewhere (2,3). Fig. 2a shows schematically the discharge vessel consisting of a cylindrical glass tube and two plane electrodes. The gas filling is hydrogen at pressures in the mbar-range. The capacitor bank is coupled to the electrodes via a high power switch (3). After triggering of the switch, the discharge starts close to the inner wall of the glass tube. Strong azimuthal magnetic fields generated by currents of up to 1 MA compress the hollow plasma cylinder towards the axis. Finally a pinch is formed on the axis, as it is illustrated in Fig. 2a. The visible plasma emission is used to diagnose the discharge dynamics. The collapse and pinch phase is observed with a streak camera, where the slit is aligned perpendicular to the axis of symmetry (i.e. the z-axis in Fig. 2a). Fig. 1 shows the corresponding streak image. The plasma sheath starts at a radius of about 7 cm and collapses to the center, forming a pinched plasma column. Typical collapse velocities range from 10 high 5 cm/s to 10 high 7 cm/s depending on the discharge parameters