Charge neutralization of heavy-ion ICF driver beams

Summary form only given, as follows. For heavy ion beams to be successful as a driver for inertial confinement fusion targets it must be possible to project a very high beam over several meters in the reactor chamber onto a spot a few millimeters in diameter. This is physically possible with ions of mass A /spl sim/ 200, energy /spl sim/ 10 GeV, and very low charge state 1-2. However, the technology is easier if beam space charge effects can be reduced without excessive increase in beam emittance. Using an electromagnetic, r-z PIC (particle-in-cell) code called BICrz, the author is modeling the processes by which an unneutralized ion beam from the accelerator becomes partially neutralized, by entraining electrons from a preexisting plasma cloud or produced by collisional ionization of chamber vapor, or perhaps other mechanisms. With focal spot size in mind, the degree of neutralization at the front and back of the pulse, and nonlinearity of the radial fields are measured.