1. FLASH. Free-Electron Laser in Hamburg Lessons from FLASH FLASH Upgrade FLASH II Lessons Siegfried Schreiber DESY FLS 2010 SLAC 1-6 March 2010

2. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg FLASH at DESY, Hamburg FLASH

3. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg FLASH at DESY in Hamburg > Single-pass high-gain SASE FEL  SASE = self-amplified spontaneous emission > Photon wavelength range from vacuum ultraviolet to soft x-rays > Free-electron laser user facility since summer 2005  1 st period: Jul 2005 – Mar 2007  2 nd period: Nov 2007 – Aug 2009  3 rd period: starting late summer 2010 > FLASH is also a test bench for the European XFEL and the International Linear Collider (ILC) > FLASH is now being upgraded in a shutdown started 21-Sep-2009 to 1.2 GeV to approach the water window

4. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg FLASH layout – after the upgrade 315 m Bunch Compressor Bypass Undulators sFLASH Bunch Compressor 5 MeV160 MeV500 MeV1200 MeV Accelerating StructuresDiagnostics FEL Experiments

5. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Electron Source: RF-Gun and Laser > New RF-Gun from PITZ with strongly reduced darkcurrent – by a factor of ~10 (at 3.8 MW) > Prepared for higher RF power > 5 MW – once a 10 MW klystron is available > Two fully diode pumped laser systems – replacing the old flash lamp pumped heads > 10 Hz operation > Improved low level RF controls of RF Gun and 1 st accelerating module > New synchronization system based on fiber laser reference – phase control over bunch train

6. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg PITZ – Photo Injector Test Stand at DESY Zeuthen > Develops electron sources for FLASH and European XFEL > Has demonstrated key parameters for the European XFEL:  low emittance  high average power operation 10 Hz, 7 MW, 0.7 ms RF pulse length ~50 kW av. power Talk on PITZ this afternoon, WG5 session

7. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Example for smaller bunch charges > Emittance approaches 0.3 mm mrad for 100 pC preliminary results 1 nC results for similar machine conditions (~3 weeks period) measurements hampered by RF phase stability issues Laser Spot Size (mm) Emittance (mm-mrad)

8. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg 3.9 GHz (3 rd harmonic) Module and Module 1 > New 1 st accelerating module with better sc cavities, now equipped with Piezo tuners > 3 rd harmonic module with four nine-cell superconducting cavities operated at 3.9 GHz  Built by FNAL in a collaboration with DESY

9. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Accelerating Modules > 7 TESLA type accelerating modules  Superconducting 9-cell Niobium 1.3 GHz cavities operated at 2 K > Electron beam energy 1.2 GeV > 7 RF stations  five 5 MW, one 10 MW multibeam klystron, one 3.9 GHz station  Pulse length 1.5 ms  10 Hz > XFEL type waveguide system on modules 1, 6, and 7  RF power to cavity pairs individually adjusted → optimization of performance

10. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg 7 th Accelerating Module > 7 th superconducting accelerating module (XFEL prototype PXFEL1) > Tested in the module test stand at DESY (CMTB) > Expected gradient more than 200 MeV – excellent state of the art cavities > Waveguide distribution system allows gradient optimization

11. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Flying modules during installation at FLASH

12. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Mounting module 7 into the FLASH tunnel

13. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg sFLASH: Experiment for Seeded FEL Radiation > Generation of seeded FEL radiation for piloting experiments > Synchronisation goal for pump probe experiments: 10 fs > Installed between the collimator and SASE undulators → new electron beamline with a length of ~ 40 m > Collaboration of DESY and U Hamburg > HHG seeding at ~ 35 nm (13 nm as an option) 4 variable gap undulators In-coupling (seed) Out-coupling (photons) Optical replica synthesizer (longitudinal beam diagnostics) Top-view sFLASH SASE undulators FLASH Exp. Hall Experimental hut

14. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg sFLASH Section with new Undulators and Mirror Chambers

15. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Undulators > High-gain single-pass SASE FEL > Fixed gap undulator  6 modules with a total length 27 m  permanent NdFeB magnets  gap 12 mm > Changing photon wavelength requires a change of the electron beam energy > Wavelength reach with 1.2 GeV = 5 nm

16. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Experimental Hall Visible Laser FIR -Beamline Plane Grating Monochromator BL3 unfocused (5 -10 mm), optional multilayer mirror in experiment for few to sub-μm focus BL2 20 μm focus BL1 100 μm focus PG2 50 μm focus, monochromatized PG1 sub-10 μm focus, monochromatized 2-stage Raman- Spectrometer (under commissioning) > ~ 95 publications on photon science at FLASH in high impact journals > ~ 50/year on technical developments  http://hasylab.desy.de/facilities/flash/publications/selected_publications http://hasylab.desy.de/facilities/flash/publications/selected_publications

17. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Photon diagnostics upgrades Experimental hall Beam distri- bution area Tunnel New installations: > Focusing mirror at BL3 > Fast switching mirror unit > Split and delay unit as a permanent device in the direct beam lines > Additional Photon beam position monitors (BPM) with MCP / fluorescence screen monitor > New online spectrometer based on atomic photoionization > Micro channel plate (MCP) / fluorescence screen monitor > and many more

18. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Online Spectrometer > Online determination of the spectral distribution using ion and electron time-of- flight spectrometer Gas inlet with ~10 -7 mbar (rare gases) Ǿ 22mm apertures at both ends > Important to tune wavelength and spectral width

19. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg User experiments at FLASH > 4 calls for proposals so far (pilot + 3 user periods) > Typically ~300 12-h shifts per period scheduled for users > 3 rd user period: 324 shifts for 28 experiment User operation FLASH Proposals (submitted / approved) Pilot experiments

20. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Organization of beam time > Beamtime is scheduled in blocks > A user block has 4 weeks > Between user blocks: 1 or 2 study weeks and 1 week user run preparation  FEL physics studies  Improvements of the FLASH facility  Preparation of the next user block (beamlines) > General accelerator studies weeks  a few blocks per year for general studies, mostly related to the European XFEL or ILC User period UserUser period 200520062007200820092010 Periods for upgrade and commissioning

21. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Organization of beam time > Up to now two periods with user experiments:  1 st period: Jul 2005 – Mar 2007  2 nd period: Nov 2007 – Aug 2009  3 rd period starts late summer 2010 > A total of 14000 hours of user beamtime > 1st → 2nd period:  Uptime 87% → 93%  45% → 49% of beamtime to users (within user periods)  30% → 33% of total time > Beam time is overbooked by a factor of ~3 > Experiments form collaborations to work more efficient > In average one experiment is scheduled for 11.6 12h-shifts  large pressure on experiments and machine to succeed in a short time

22. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Beam time distribution during 2 nd user period FEL user experiments 49% FEL studies + user preparation 30% Scheduled off 11 % Accelerator studies 10% SASE FEL radiation delivery 78 % Set-up 1 % Tuning 14 % Down 7 % up-time during user experiments: 93% Nov-26, 2007 – Aug-16, 2009

23. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg SASE Tuning for Experiments Wavelength changes 55% Intensity, position, etc. 17 % After failures 7% Quality 8% narrow bandwidth, exact wavelength, etc. After maintenance 6% Single, multi, (long), rep.rate 5% > Wavelength has been changed ~ 140 times > Tuning time required for wavelength changes is typically ~ 2 hour Other 2% scheduled 48 hours to setup 5 th harmonic of 8 nm Time used for wavelength changes / week hours # user week 2 nd user period

24. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Photon Wavelengths > More than 30 different wavelengths between 6.8 nm and 40.5 nm delivered for users > Most favorite wavelengths  around 7 nm - as short as possible  around 13.5 nm - availability of multilayer mirrors, best compromise with other users > Experiments using higher harmonics  3rd harmonic of 7 nm  5 th harmonic of 8 nm  3 rd harmonic of 40.5 nm > Shortest wavelength delivered  1.59 nm (5 th harmonic of 7.97 nm)

25. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg SASE performance Typical user operation parameters Wavelength range (fundamental) 6.8 – 47 nm Average single pulse energy 10 – 100 µJ Pulse duration (FWHM) 10 – 70 fs Peak power (from av.) 1 – 5 GW Average power (example for 500 pulses/sec) ~ 15 mW Spectral width (FWHM) ~ 1 % Peak Brilliance 10 29 - 10 30 B B = photons/s/mrad 2 /mm 2 /0.1%bw Multibunch SASE signal (µJ)

26. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Summary Upgrade 2009 / 2010 > Upgrade shutdown started September-21, 2009 > Technical commissioning started February-15, 2010 > First beam expected in April, user runs to be started in late summer 2010 upgraded photon diagnostics and beamlines new RF gun7 th accelerating module seeding experiment sFLASH + redesigned electron beamline transverse deflecting cavity + spectrometer arm / tuning dump 3 rd harmonic module + RF station exchanged 1 st accelerating module additional RF station + exchanged RF station exchanged RF stations optimized llrf controls new synchronization and feedback systems improved survey and alignment of accelerator components (incl. SASE undulators) upgraded magnet controls upgraded personnel interlock und radiation safety systems upgraded and optimized waveguide distribution new diode pumped photocathode laser; upgraded old laser system installation of a second master oscillator (as backup) new cabling/layout injector llrf electronics maintenance of infrastructure: water supplies, cryogenics exchanged injector steerers

27. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Upgrade Status > Upgrade in schedule – technical commissioning started > First beam to be expected mid April > Commissioning until summer: Main goals:  lasing with wavelength below 5 nm  tailor phase space using the 3 rd harmonic cavities to improve lasing and to have more flexibility in FEL pulse length  routine operation with long bunch trains and improved synchronization  stable seeding in sFLASH

28. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Compression Scheme w/o 3 rd Harmonic Cavities > Non-linearity in the longitudinal phase space leads to a roll-over compression → development of a sharp spike ~ 50 fs with high peak current > Very sensitive to phase and orbit changes in the collimators Z (mm) 2 mm 1 MeV Z (mm) 2 mm 1 MeV Energy (MeV) Z (mm) 2 mm 1 MeV Current (A) 40 A 2 mm 1.5 kA 0.5 mm 1 mm 400 A

29. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Compression Scheme w/o 3 rd Harmonic Cavities > Non-linearity in the longitudinal phase space leads to a roll-over compression → development of a sharp spike ~ 50 fs with high peak current > Very sensitive to phase and orbit changes in the collimators Z (mm) 2 mm 1 MeV Z (mm) 2 mm 1 MeV Energy (MeV) Z (mm) 2 mm 1 MeV Current (A) 40 A 2 mm 1.5 kA 0.5 mm 1 mm 400 A Measured longitudinal shape of a compressed bunch Measured by a transverse deflecting cavity placed after the last accelerating module

30. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg 2 mm Compression with and w/o 3 rd harmonic cavities > Non-linearity in the longitudinal phase space leads to a roll-over compression → development of a sharp spike ~ 50 fs with high peak current > Very sensitive to phase and orbit changes in the collimators Z (mm) 2 mm 1 MeV Z (mm) 2 mm 1 MeV Energy (MeV)Z (mm) 2 mm 1 MeV Without 3 rd harmonic cavities With 3 rd harmonic cavities 50 μm

31. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Regular Compression with 3 rd Harmonic Cavities > Flattening of the longitudinal phase space > More regular compression with high peak current > About a factor of ~10 more photon energy, longer pulses ~150 fs 50 A Current (A) S (mm) 200 A Current (A) S (mm) 2.4 kA Current (A) S (mm) 315 m Bunch Compressor Bypass Undulators sFLASH Bunch Compressor 5 MeV160 MeV500 MeV1200 MeV Accelerating StructuresDiagnostics FEL Experiments Charge: 1 nC 100 μm 1 mm 5 mm

32. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Expected Photon Energy and Pulse Length > Regular compression scheme with 3 rd harmonic cavities, charge 1 nC → larger single pulse energy, pulse lengths ~100 fs > Compression Schemes with lower bunch charge → short pulses down to ~5 to 50 fs 1 nC 0.25 nC 0.02 nC Radiation pulse width (RMS) 0. 25 nC 1 nC Radiation pulse energy/charge (av.) 0. 02 nC Undulator length z (m) Pulse energy/Charge (μJ/nC) rms Pulse Length (fs)

33. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Synchronization and Beam Based Feedbacks > Even with an excellent energy stability of ~1 10 -4 the magnetic chicane bunch compressors translates this into arrival time jitter > Also phase jitter of laser/ RF Gun contributes plus various sources of slow drifts > jitter and drift along the bunch trains → synchronization system based on stable fiber lasers → beam picks-ups and other instrumentation at various places along the linac → feedbacks using this information → successful tests with prototypes of these pick-ups (BAMs) (2008) 40 fs rms achieved – goal: 10 fs 2008 data

34. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Layout of the Synchronization System > Most components will be ready for the FLASH start-up > Synchronization and beam based feedbacks need careful commissioning > In close cooperation with users, especially with pump-probe experiments

35. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Operation with Long Electron Bunch Trains > FLASH will (again) offer trains of a few hundred pulses at 10 Hz  number of pulses / train depends on the pulse spacing within the train, and on the demands concerning the photon beam parameters > Lasing with 800 bunches / train (1 MHz bunch spacing, 5 Hz rep. rate) demonstrated in spring 2007, user runs in 2008 > Long train operation has not been possible for a year due to a leak in the dump line > Successfully repaired in August 2009, new dump line and new diagnostics and loss monitors tested successfully in Sep 2009 > Full beam-loading experiment in Sep-2009  800 bunches at 1 MHz stable, 2400 bunches demonstrated  ILC driven international collaboration

36. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Long Bunch Train Run at 7 nm in 2008 > 100 bunches 500 kHz for two experiments in March 2008 > Wavelength: 7.05 ± 0.1 nm > Average SASE level ~30 μJ (14 mW average power) Wavelength (nm) Bunch Number

37. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg FLASH II – 2nd Undulator Line and Experimental Hall > Common proposal by DESY and HZB with participation of PSI > In planning phase, kick-off meeting 28-Jan-2010 FLASH II FLASH

38. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg FLASH II layout > Main features: Seeding and polarized radiation > Extend user capacity with SASE and HHG/HGHG seeding > Tunability of FLASH II by moveable undulator gap > Using existing infrastructure > Separation FLASH and FLASH II behind last accelerator module 315 m Bunch Compressor Bypass Undulators sFLASH Bunch Compressor 5 MeV160 MeV500 MeV1200 MeV Accelerating StructuresDiagnostics FEL Experiments

39. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg FLASH FLASH II FLASH II EXP HALL PETRA III Extraction area Artist view of FLASH II

40. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Lessons The upgrade plans I showed actually reflect many lessons we learnt from 4 years of user operation FEL experiments – accelerator > Close cooperation of accelerator and FEL users is essential for success  experimental success often depends on fine adjustment of beam parameters  example: 5 th harmonic experiment at 1.59 nm > Machine upgrades need to be planned and discussed together with users to understand their needs  short wavelength (water window), better synchronization (to fs level) and stability (seeding), fast tuning of wavelength (variable gap), polarization (left and right) > On the other hand, users need to understand the potential and the limitations of the facility > Users need to be prepared to take advantage of hundreds or thousands of bunches per second and need to be able to cope with the burst structure  requires new experimental techniques and detectors > Electron and FEL beam data must be acquired (DAQ) and need to be provided to users – since they are essential for their data analysis

41. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Lessons Organization of experiments > Every experiment has quite different demands on the FEL beam and need to be accounted for > Flexibility in FEL beam properties required  single pulse energy, number of bunches per sec, distance between bunches, wavelength, spectral width, arrival time stability and so on  frequent changes of beam parameters (from shift to shift, even within shifts) > Bundling of experiments with similar requirements and good preparation of the run > Serving a single user at a given time not very efficient (→ FLASH II) > The often complex experiments need a long preparation phase, but have only a very short running time (11.6 shifts) and a long time spans between experiments

42. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Lessons Stability of Beam > An excellent stability of the beam is essential (sounds trivial…) > The llrf system turns out to be a key issue for good beam quality: the long rf pulses and high beamloading together with the complicated compression scheme requires tight tolerances in amplitude and phase stability which have to be met > To complete the llrf system, synchronization to the fs level and beam based feedbacks are important for many experiments > Climate needs to be taken into account  in Hamburg we observe a large difference between summer and winter runs - especially the summers are quite hot and produce difficulties > As much non-destructive diagnostics as possible, both for electrons and FEL beam  we need to access the longitudinal phase space (slice parameters) with high precision (fs)  online FEL beam parameters (energy, position, spectrum) > Operators do have difficulties to learn to run FLASH  efficient operation needs many tools and procedures especially restore procedures,  operator training

43. Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010 FLASH. Free-Electron Laser in Hamburg Summary > FLASH finished in August 2009 a very successful 2 nd user period > ~ 95 publications on photon science at FLASH up to now > Upgrade shutdown started in autumn 2009, beam to be expected in April 2010 > Major modifications of FLASH  energy reach of 1.2 GeV to approach wavelengths below 5 nm  shaping of longitudinal phase space with 3 rd harmonic module  synchronization to 10 fs level with new system based on fiber lasers  sFLASH: test of seeding option > One aim is it to provide routinely long bunch trains to users > FLASH II in sight: seeding and polarization  Second undulator beamline + new experimental hall (FLASH II) in the planning phase