Ion trap physics in a spherical IEC

Summary form only given, as follows. The spherical inertial electrostatic confinement (IEC) is of interest as a near-term neutron source and as a future alternate fusion power concept. In spherical inertial confinement devices, virtual cathode-anode formation creates an ion trap, improving ion confinement and increasing beam-beam fusion reactions. First proposed by Farmsworth and Hirsch, ion trap formation, (or multiple traps called "poissors") has been questioned. However, recent experimental studies at the University of Ilinois using collimated detection of D-D protons have demonstrated trap evolution once the IEC operation exceeds a critical pervance value of 1-2 I(mA)/V(kV)/sup 3/2/ in deuterium. In this small device, the background neutrals are not yet "burned out", so the earlier trap theory must be extended to this case. Charge-exchange plays two key roles in the dynamics: the energy spread of ions entering the trap region is narrowed and trapped thermalized ions are preferentially removed. This model for trap dynamics and corresponding measurements will be discussed.