Paul Scherrer Institut Sven Reiche SwissFEL Design PSI, PSI, 13. September 2018 13. September 2018

Design Goals for SwissFEL Compact FEL Facility , reaching 1 Ångstrom: Low beam energy Compact undulator Low Emittance Gun Short period undulator with sufficient gap and ield strength (K>1) lu = 15 mm, K = 1.2  E = 5.8 GeV, en = 0.43 mm mrad PSI, 13.09.2018

Design Goals for SwissFEL SwissFEL facility covers 0.1 – 7 nm with 1- 5 nm seeded, variable polarization > 1nm Natural cut of wavelength range by photon optics (0.1-0.7 nm and 0.7 – 7 nm) Tuning of hard X-ray FEL (ARAMIS) mostly by beam energy (2- 5.8 GeV) (K value allows only small tuning) Tuning of soft X-ray FEL (ATHOS) by K-value and beam energy Independence of both beamlines ATHOS is instrumented with APPLE II type undulator modules with 4 cm period (K=1-3.5) Self-seeding scheme preferred over EEHG and HHG seeds PSI, 13.09.2018

Expected FEL Performance of ARAMIS @ 1 A FEL Beam Design Parameters Nominal Operation Mode Special Operation Mode Long Pulses Short Pulses Large Bandwidth Ultra-Short Pulses Undulator period (mm) 15 Undulator parameter 1.2 Energy spread (keV) 350 250 17000 (FW) 1000 Saturation length (m) 47 50 Saturation pulse energy (µJ) 150 (*) 3 100 Effective saturation power (GW) 2.8 0.6 2 Photon pulse length (fs, rms) 21 2.1 0.06 Beam radius (µm) 26.1 17 26 Divergence (µrad) 1.9 2.5 Number of photons (×109) 73 1.7 7.5 Spectral Bandwidth, rms (%) 0.05 0.04 3.5 (FW) Peak brightness (# photon/mm2.mrad2.s1.0.1% bandwidth) 7.1032 1.1032 8.1030 1,3.1033 Average brightness (# photon/mm2.mrad2.s1.0.1% bandwidth) 2,3.1021 5,7.1018 3.1019 7,5.1018 PSI, 13.09.2018

Layout SwissFEL 600 m Technology choice: RF photo-electron gun (2.5 cell), S-band 2 Stage compression at highest energy possible to minimize RF tolerances C-band linac (less RF stations, real estate and mains power than S-band, chirp removal after BC 2) X-band for linearizing phase space before BC 1 2 bunch operation (28 ns) with distribution to Aramis and Athos at 100 Hz Laser Heater to mitigate microbunch instability PSI, 13.09.2018

Microbunch Instability – Gain Curve for SwissFEL sd = 5e-5 PSI, 13.09.2018

Laser Heater Layout ✜ ✜ ✜ ✜  ✜  ✜ BPM X [m] Screen ICT BAM BLM    ✜ ✜ ✜ ✜     ✜ BPM X [m]  Screen  ICT  BAM  BLM ✜   Steerer Z [m] PSI, 13.09.2018

Laser Heater Schematic PSI, 13.09.2018

Laser Heater Specification/Interface Two bunches with 28 ns separation, diagnostic must resolve both bunches and laser pulses EPICS control system mandatory, following the PSI/SwissFEL naming convention Actuator/Sensor of the feedback system must have a RocketIO interface (same for machine protection) Laser position, intensity and overlap must be part of the feedback system. Modulator undulator will be built by STFC/Daresbury Dipole magnets will be built by PSI Electron beam diagnostic will be built by PSI (including the overlap screens in the chicane) Vacuum chamber within the laser heater has an inner diameter/height of 16 mm. Undulator and Vacuum chamber will be movable between two fixed position (on/off position) Contributed by the collaboration: Vacuum chamber Movers for vacuum chamber and undulator Laser transport & laser diagnostic (arrival time, overlap, intensity for set-up & feedback) Mechanical support and girder PSI, 13.09.2018

Time Schedule PSI, 13.09.2018