Speaker
Description
Static linear focusing is a standard part of photoinjector emittance compensation. It can reduce slice-envelope mismatch, but it cannot in general make all slice envelopes evolve identically. We study this limitation using the envelope-slope ratio α = r′/r, where r is the slice envelope and r′ is its derivative along the beamline. We then explore the use of azimuthally modulated EM modes to remove the non-linear residual phase space distortions due to space charge. Several independent Bayesian optimisation runs converge to the same sparse solution, with only TE31 retaining a finite amplitude. In the best case, the final projected normalised emittance objective is improved by 12.6%. Sensitivity scans in gun phase and solenoid current show that this improvement persists over a finite but bounded region. Our main outcome is a TE31-dominated beam-dynamics working point.