Physical Review Accelerators and Beams (Aug 2022)
Slice energy spread measurement in the low energy photoinjector
Abstract
Slice energy spread is one of the key parameters in free electron laser optimizations, but its accurate measurement is not straightforward. Two recent studies from high energy (≥100 MeV) photoinjectors at SwissFEL and European x-ray free electron laser (XFEL) have reported much higher slice energy spread than expected at their XFEL working points (200–250 pC). In this paper, a new method for measuring slice energy spread at lower beam energy (∼20 MeV) is proposed and demonstrated at the PhotoInjector Test facility at DESY Zeuthen, and the results for 250 pC are much lower than those measured at high energy injectors.