Heavy ion beam degradation from stripping in near vacuum reactor chambers

With the use of a particle simulation code we have investigated the ballistic transport of heavy ion beams through a gas-filled reactor for inertial confinement fusion. The background gas pressure has been taken to be 10⁻⁴ torr–10⁻³ torr of Lithium vapor as is appropriate to the HYLIFE reactor (1) concept. During transport to the pellet, Coulomb collisions of beam particles with the background gas will convert a fraction of the beam to charges states higher than the initial value. Collisions will also produce an associated swarm of knock-on electrons. As the beam approaches the pellet, anharmonic components of the space charges forces will lead to a distortion of the phase space of the beam and a consequent degradation of the focal properties of the beam. This degradation can be described in terms of an increase in the rms emittance of the beam (2). The degree of emittance growth depends sensitivity upon the initial spatial distribution of particles in the beam.