Preliminary Results of a Novel Designed 7.7 kJ Plasma Focus Device with Hemisphere Electrodes

The Hemisphere Plasma Focus Device, a new construction of plasma focus devices is constructed and operated with total energy of 7.7 kJ. The discharge takes place between two concentric hemispherical electrodes. The plasma sheath is accelerated and confined by electromagnetic force. Rogowiski coil and potential divider are used to characterize the discharge current, the discharge voltage and obtain the pinch effect in shape of sharp crevice. The deposited energy is about 31.5% of the input energy for 6kV charging voltage. The total system inductance is about 285 nH with low resistance of about 23 mΩ. The plasma inductance has maximum value at the pinch time. The pinch time decreases by increasing input energy and also by decreasing the helium gas pressure. The average sheath velocity varies in range between 1.5 and 2.7 cm/µs which indicates that the charge state is about 2 and plasma temperature should mostly be over 11.2eV.