Bunch length measurement setup for femtocoulomb bunch charges at the superconducting Darmstadt electron linear accelerator S-DALINAC

A new bunch length measurement system has been implemented at the superconducting Darmstadt electron linear accelerator (S-DALINAC). Optical transition radiation pulses are created from the electron beam when it hits a smooth conducting surface, having the same duration as the electron bunches. A streak camera is used to measure the duration of the light pulses to determine the bunch lengths. The new setup can be deployed easily at multiple locations to track the evolution of the bunch length along the beamline. Commissioning measurements were performed using the normal-conducting buncher cavity, a superconducting cavity of the injector linac, and the injector arc of the S-DALINAC. From these measurements, both the bunch length and the longitudinal dispersion of the injector arc were obtained. The measurement process and typical measurement results are presented and discussed.