Beam mismatch and emittance oscillations in magnetic transport lines

The behavior of axisymmetric space-charge dominated beams in magnetic transport lines is examined using numerical simulation. A transport line containing two linear focusing solenoids used to match a continuous, unneutralized beam from an ion source to a radio-frequency quadrupole (RFQ) is considered. The beam evolution is compared for beams with different initial emittances and density profiles. The initial emittance growth caused by nonlinear space-charge forces for a drifting beam expanding from a waist can be described by a universal curve. Subsequent emittance oscillations in the transport line result in beam mismatch at the RFQ entrance, but the effects diminish with increasing initial emittance.>