The effect of the initial gas density and gas shell profile in a small gas-puff Z-pinch

The authors determined the thickness and mass of the initial gas shell from three different kinds of nozzles and measured the corresponding X-ray yield (2 kev < hv < 6 kev) in a small gas-puff Z-pinch device which consists of a fast valve, a supersonic nozzle of Mach 4 and a capacitor bank charged to 25 kv-30 kv. The authors also studied the plasma dynamics with laser differential inteferometery. The experimental results have revealed that the thinner gas shell creates higher implosion velocity, higher X-ray yield and smaller minimum radius of the pinched plasma column. For example, the thickness of gas shell is 18 mm and 4 mm respectively for No.1 and No.3 nozzle, their corresponding maximum implosion velocities are 12.7 cm/us and 16.4 cm/us, their X-ray yields are 0.21 J/shot and 0.32 J/shot. This phenomenon might be explained in the following way: As the thinner gas shell has a small mass, the velocity of plasma will be higher under the same discharge current, producing higher temperature and higher x-ray