Tarantula¿100 kV pinch discharge apparatus for studying shock waves

An experimental apparatus for research on powerful shock waves in a plasma is described. The shock waves are produced by the cylindrical compression of a plasma by the pinch effect. The experiment is performed in a fused-silica discharge tube im long by 0.5 m bore. An initial axial magnetic field of up to 0.5 Wb/m2 is provided. A low-pressure gas in the tube is preionised by using various capacitor discharge circuits. A high voltage is then applied inductively between the end electrodes of the tube from a low- inductance circuit. This circuit, which stores up to 100 kJ at 100 kV, is switched by 40 spark gaps and can deliver up to 1 MA with a peak of dI/dt of 2.5 TA/s. These high currents generate large impulsive forces which, without care, could damage the fragile silica tube. This tube is held in place by silicone rubber which also provides the main insulation. The design and operation of the apparatus are described with particular emphasis on the two major problems encountered: (a) switching the 100 kV circuit and (b) providing insulation and support for the silica tube.