Single-shot transverse coherence in seeded and unseeded free-electron lasers: A comparison

The advent of x-ray free-electron lasers (FELs) drastically enhanced the capabilities of several analytical techniques, for which the degree of transverse (spatial) coherence of the source is essential. FELs can be operated in self-amplified spontaneous emission (SASE) or seeded configurations, which rely on a qualitatively different initialization of the amplification process leading to light emission. The degree of transverse coherence of SASE and seeded FELs has been characterized in the past, both experimentally and theoretically. However, a direct experimental comparison between the two regimes in similar operating conditions is missing, as well as an accurate study of the sensitivity of transverse coherence to key working parameters. In this paper, we carry out such a comparison, focusing in particular on the evolution of coherence during the light amplification process

Start-to-end simulations for the soft X-ray FEL at the Max IV laboratory

A Soft X-ray FEL (the SXL) using the existing 3 GeV linac at the MAX IV Laboratory is currently in the design phase. In this contribution, start-to-end simulations, including the photo-injector simulations using ASTRA, the linac simulations using ELEGANT and the FEL simulations using GENESIS, are presented for 100 pC and 10 pC operation modes. The features of the electron beam from the MAX IV linac and their impact on the FEL performance are discussed