Potential additional beam loss from energy discrepancy due to dipole–kicker-induced RF phase changes

Ascertain whether the energy discrepancy between bunch modes, introduced by effective RF phase differences arising from dipole–kicker combinations in bunch compressors, causes additional beam loss—particularly of halo particles—under CW XFEL operation where RF voltage cannot be rapidly adjusted due to high cavity quality factors.

Background

In the dipole–kicker scheme, altering R56 changes the path length and arrival time, which leads to variations in effective RF phase and consequently energy gain downstream of the chicane. Due to the high Q-factor of superconducting cavities, rapid RF adjustments are not feasible to compensate for these energy differences.

The authors highlight that such energy discrepancies may produce optics mismatches and potentially induce beam losses, especially of halo particles. Whether this occurs—and to what extent—remains uncertain and requires investigation to ensure reliable and safe operation.