Soft x-ray seeding studies for the SLAC Linac Coherent Light Source II

• Main Authors: E. Hemsing, G. Marcus, W. M. Fawley, R. W. Schoenlein, R. Coffee, G. Dakovski, J. Hastings, Z. Huang, D. Ratner, T. Raubenheimer, G. Penn
• Format: Article
• Language: English
• Published: American Physical Society 2019-11-01
• Series: Physical Review Accelerators and Beams
• Online Access: http://doi.org/10.1103/PhysRevAccelBeams.22.110701

We present the results from studies of soft x-ray seeding options for the LCLS–II x-ray free electron laser (FEL) at SLAC. The LCLS-II will use superconducting accelerator technology to produce x-ray pulses at up to 1 MHz repetition rate using 4 GeV electron beams. If properly seeded, these pulses will be nearly fully coherent, and highly stable in photon energy, bandwidth, and intensity, thus enabling unique experiments with intense high-resolution soft x-rays. Given the expected electron beam parameters from start to end simulations and predicted FEL performance, our studies reveal echo enabled harmonic generation (EEHG) and soft x-ray self-seeding (SXRSS) as promising and complementary seeding methods. We find that SXRSS has the advantage of simplicity and will deliver 5-35 times higher spectral brightness than EEHG in the 1–2 nm range, but lacks some of the potential for phase-stable multipulse and multicolor FEL operations enabled by external laser seeding with EEHG.