We report an on-going temporal characterization project and method on a shot-to-shot basis for free electron laser pulses by using THz photoelectron spectroscopy at the European XFEL facility. Shot to shot FEL time jitter and pulse profile information can be reconstructed by resolving the photoelectrons energy spectra in an external THz field. Laser based THz generation and optimization, photoelectron generation and detection are described. Further considerations of the temporal resolution based on proposed photoelectron lines are presented and intuitive simulations are made to demonstrate the feasibility of such technique.
SwissFEL is the Free Electron Laser (FEL) facility under construction at the Paul Scherrer institute (PSI), aiming to provide users with X-ray pulses of lengths down to 2 femtoseconds at standard operation. The measurement of the length of the FEL pulses and their arrival time relative to the experimental laser is crucial for the pump-probe experiments carried out in such facilities. This work presents a new device that measures hard X-ray FEL pulses based on the THz streak camera concept. It describes the prototype setup called pulse arrival and length monitor (PALM) developed at PSI and tested in Spring-8 Angstrom Compact Free Electron Laser (SACLA) in Japan. Based on the first results obtained from the measurements, we introduce the new improved design of the second generation PALM setup that is currently under construction and will be used in SwissFEL photon diagnostics.