Discharge characteristics of the spherical inertial electrostatic confinement (IEC) device

The University of Illinois inertial electrostatic confinement (IEC) device provides 10/sup 7/ 2.5 MeV D-D neutrons/second when operated with a steady-state deuterium discharge at 70 kV. Being compact and lightweight, the IEC potentially represents an attractive portable neutron source for activation analysis applications. The plasma discharge in the IEC is unique, using a spherical grid in a spherical vacuum vessel with the discharge formed between the grid and the vessel wall, while the -70 kV grid (cathode) also serves to extract high-energy ions. Two key features of the IEC discharge are discussed: 1) the breakdown voltage characteristics as a function of pressure-grid/wall distance (pd), and 2) the formation of ion "microchannels" that carry the main ion flow through grid openings.