Studies of the collective focusing ion accelerator

The collective focusing ion accelerator uses the strong electrostatic focusing of an electron cloud to radially confine an ion beam which is accelerated in a glass torus. A "bumpy" toroidal geometry is produced by using 16 discrete field coils, forming a series of 16 mirror cells around the torus. This configuration prevents the electrons from being accelerated by the toroidal electric field used for accelerating the ions. To load the entire torus with electrons a separate thermionic emitter is required for each cell. The electron cloud is trapped and compressed nearly adiabatically by the rising toroidal magnetic field, and is subsequently stable for the lifetime of the field. A flashboard injector introduces deuterium ions at a mirror plane where the electron density is minimum so that they are not electrostatically trapped toroidally by the electrons. Their low magnetic moment insures they are not also trapped by the mirrors. Conversely, the electrons are seen to be trapped even under ion acceleration conditions. Since the ion source must be on the surface of the torus, the radial field of the electron cloud is used to compress the ions to the toroidal axis by delaying the ion injection relative to that of the electrons. To date the injection and containment of the electrons is well developed, and the details of injection and acceleration of the ions is under study.