Collimation and decoupling of ECR source beams for brilliance optimization

The four-dimensional transport of the transverse phase space of the extracted beam was calculated for the CAPRICE electron cyclotron resonance (ECR) ion source at GSI. It is especially of interest for an ECR ion source, where asymmetric beams of the transverse phase spaces are extracted in the presence of a strong solenoidal field, and this axial magnetic field adds an angular momentum to extracted beam, resulting in a strong horizontal and vertical (x–y) coupled beam. The paper presents multi-particle tracking simulations using the well-established particle-in-cell code BEAMPATH. The results illustrate that the beam brilliance can be improved by combination of multi-stage collimation with skew quadrupole decoupling.