The BESSY Soft XRay SASE FEL Free Electron

The BESSY Soft X-Ray SASE FEL (Free Electron Laser) The BESSY Soft X-Ray SASE FEL Roland Müller EPICS Meeting Spring `02, BESSY, Berlin

Classical FEL Scheme SASE FEL Scheme (Self Amplified Spontaneous Emission)

SASE-FEL Setup

History of SASE 1980 1996 Dec. 1999 Feb. 2000 Sep. 2000 Feb. 2001 Apr. 2001 Sep. 2001 Oct. 2001 First proposal First experimental observation UCLA: = 16 m APS: lasing at = 523 nm DESY: lasing at = 80 nm APS: saturation at = 523 nm VISA/BNL: saturation at = 800 nm APS: saturation at = 385 and = 265 nm DESY: saturation at = 100 nm First user experiments @ DESY-TTF Development steps towards VUV and X-ray FELs

SASE FEL User Facilities Under construction and/or operational • TTF / DESY* • LEUTL / APS* > 6 nm (80 nm) > 120 nm (265 nm) Proposed • • • BESSY SLAC SPring 8 TESLA ELETTRA, ³ 1. 2 nm (1 ke. V) ³ 1. 5 Å (8 ke. V) ³ 15 nm 3. 6 nm ³ 0. 85 Å (14 ke. V) ENEA, Daresbury …. . . 0. 1 nm * Hybrid between FEL development & user facility

TESLA X-ray FEL > 0. 85 Å (14 ke. V): X-rays linear collider

TTF FEL: TESLA Test Facility > 6 nm (200 e. V): VUV & XUV

User Feedback Important issues: • Photon energy: …………… 20 e. V - 1. 0 ke. V (60 £ £ 1. 2 nm) • Micro-pulse duration: …………… t £ 20 fs • Narrow spectral width: …………… / £ 10 -4 • Synchronization with fs lasers • As many as possible photons per pulse • High average brilliance Proposal: FEL user-facility that becomes operational after 2007

The BESSY FEL 1. 5 - 2. 25 Ge. V linac multiple undulators TESLA module drift for monochromators and beam-blowup 3 rd extraction harmonic cavity bunch compressor BESSY II undulator UE 46 injector

The BESSY FEL Separate focussing undulator (control of the b-function)

The BESSY FEL Injector Hall BESSY II Linac Tunnel Cryogenic Hall > 1. 2 nm (1 ke. V): VUV & soft X-rays Experimental Hall

Performance

The BESSY Soft X-Ray SASE FEL COMPLEMENTARITY of the VUV and X-RAY FEL VUV and SOFT X-RAYS BESSY FEL 20 e. V to 1 ke. V 1 m. J 200 fs to 20 fs 1 k. Hz (1 -25 pulses) PHOTON ENERGY PULSE LENGTH REPETITION RATE X-RAYS TESLA X-FEL 500 e. V to 15 ke. V 1 m. J 100 fs 5 Hz (7200 pulses)

Critical Issues +For any SASE-FEL Project: – Stability of the electron beam – Diagnostics – Spiking nature of the SASE-FEL radiation – Synchronization with other laser sources +Specific for the BESSY SASE-FEL: – Cryogenic requirements (15 MV/m, cw) – Optimization of the photo-injector – Beamlines

Summary (1) Building of a “basic” FEL user facility (based on super-conducting linac technology from DESY) Goal: +construction of a SASE-FEL for the UV to soft X-ray spectral range +construction of three parallel SASE-FEL beamlines +Synchronization with conventional fs laser-sources: jitter £ 200 fs (rms) Critical tasks: Major cost factors: +Injector system +Civil engineering +Cryogenic plant +Accelerators +Undulators +Beamlines +Bunch compressors +Diagnostics +Feedback (Microphonics, Timing …) +Beamlines

Summary (2) Implementing FEL enhancements* + Enhancing the spectral resolution: / = 10 -3 <10 -4 (Seeding) + Shortening the micro-pulse duration: t = 160 fs 20 fs ? fs + Flexible FEL output (fast scanning, chirping, etc. ) + Increasing the average brilliance *Not all enhancements can be obtained simultaneously