Commissioning and Diagnostics Development for the New Short-Pulse Injector Laser at FLASH

In order to extend the parameter range of FLASH towards shorter electron pulses down to a few fs SASE pulses, shorter bunches with very small charges of a few tens of picocoulombs are necessary directly at the photo injector. Therefore a new injector laser delivering pulses of 1 to 5 ps has been installed and commissioned. The influence of the laser parameters on the electron beam was studied theoretically. In this paper we discuss the required laser beam diagnostics and present measurements of critical laser and electron beam parameters