Dependence of neutron yield on the deuterium filling pressure in a plasma focus device

A Mather-type plasma focus device (32 μF, 4 kJ), called Hanyang University Plasma Focus device, is developed as a prototype device for the irradiation test of neutrons for electric probes and cables to be used in Korea Superconducting Tokamak Advanced Research with pure deuterium gas. The six different lengths of electrode are used in order to see the dependence of neutron yield on the deuterium filling pressure at given system conditions such as capacitance, currents and inductance, after optimizing the focusing condition in terms of electrode length versus filling pressure. The relationship between the pressure and electrode length is to be fitted well by the snow-plow model. The neutron fluence and angular distribution are measured at the angles of 0 deg., 25 deg., 60 deg. and 90 deg. by locating the bubble neutron dosimeter at a distance 30 cm from the inner electrode head at each electrode length. The anisotropic factor tends to increase with pressure and the total neutron yield is strongly dependent on the isotropic emission. The maximum neutron yield is estimated to be about 1.6 x 108 (n/shot) at a pressure of 3.4 Torr