Neutron production rate and plasma characteristics of spherically convergent beam fusion

Experimental and simulation results of a spherical glow discharge for a portable neutron source are presented. The experimental device is a 45-cm-diameter, 31-cm-high stainless-steel cylindrical chamber, in which a spherical mesh-type anode 30 cm in diameter is installed. The spherical grid cathode consists of 2.0-mm-diameter stainless-steel wire, which is made into an open spherical grid of 5-cm diameter. The system is maintained at a constant pressure of 1 to 15 mTorr by feeding hydrogen or deuterium gas. The basic characteristics of breakdown voltages versus pressure and electrostatic potential profiles were measured for hydrogen discharge. Using deuterium, a steady-state neutron production of 104 s–1 was observed at a discharge of 40 kV, 2 mA. Motions of ions and electrons in the device were simulated by using a particle code, which is one-dimensional in coordinate system and two-dimensional in velocity space. It was confirmed by both the measurement and simulation that a virtual anode is formed in the central part inside the grid cathode. © 2001 Scripta Technica, Electr Eng Jpn, 135(2): 1–8, 2001