Rapidity of resonant kicker flanks returning to zero between successive bunches

Determine the achievable rise and fall times of resonant kicker magnet pulses used to implement dipole–kicker-based compression switching in continuous-wave X-ray free-electron lasers with microsecond bunch spacing, ensuring that both flanks of the magnetic field waveform return to effectively zero before the next bunch arrives to avoid residual kicks.

Background

The proposed scheme integrates fast kickers into bunch compressor chicanes to adjust the longitudinal dispersion R56 on a bunch-by-bunch basis, enabling multi-bunch-length operation in CW XFELs such as SHINE. Implementing this approach depends critically on kicker performance, including switching speed, stability, and field strength.

While resonant kickers at SwissFEL demonstrate suitable properties, the authors note uncertainty about how quickly the magnetic field decays (flanks going to zero) before the next bunch arrives, which is essential at MHz repetition rates to prevent unintended kicks and preserve beam quality. Clarifying this timing behavior is necessary to validate the feasibility of the scheme for CW operation.