The Next Generation Light Source Test Facility at Daresbury

1. The Next Generation Light Source Test Facility at Daresbury Jim Clarke ASTeC, STFC Daresbury Laboratory Ultra Bright Electron Sources Workshop, Daresbury, June 2011

2. Context: NLS – UK FEL Project 1. Photon energy range and tunability: FEL1 @ 50 – 300 eV FEL2 @ 250 – 850 eV FEL3 @ 430 – 1000eV 2. Repetition rate: 1 kHz with an upgrade path to 1 MHz 3. Pulse length & pulse energy: 20 fs FWHM photon pulse length at all photon energies 1011 photons/pulse at 1 keV – upgrade path to sub-fs pulses 4. Transverse and longitudinal coherence 5. Polarisation: FEL1 & FEL2: complete polarisation control FEL3: at least horizontal and circular polarisation over the full range 430-1000 eV.

3. NLS Layout • 2.25 GeV, 1 kHz rep rate increasing in phases to 1MHz • 3 independent FELs with variable gap undulators • SC Linac

4. FEL Hall Layout

5. Science Case and CDR • Strong science case developed and accepted, published July 2009 • The CDR was published in May 2010 • But project put on hold for 3 to 5 years • UK maintains clear ambition for a next generation light source • Reports and more information available atwww.newlightsource.org

6. Next Step • Take advantage of the project ‘pause’ to carry out targeted R&D • A key part of this will be a light source test facility • To test new ideas and concepts • Enhanced radiation output (short pulses, coherence, high harmonics, stability, ...) • New technologies (diagnostics, synchronisation, LLRF, undulators, ...) • More compact solutions – more economic • ... • To reduce the risks for a future light source facility (time, cost, quality)

7. Ultimate Aim • To develop a normal conducting test accelerator able to generate longitudinally and transversely bright electron bunches and to use these bunches in the experimental production of stable, synchronised, ultra short photon pulses of coherent light from a single pass FEL with techniques directly applicable to the future generation of light source facilities. • Stable in terms of transverse position, angle, and intensity from shot to shot. • A target synchronisation level for the photon pulse ‘arrival time’ of better than 10 fs rms is proposed. • In this context “ultra short” means less than the FEL cooperation length, which is typically ~100 wavelengths long (i.e. this equates to a pulse length of 400 as at 1keV, or 40 as at 10 keV). A SASE FEL normally generates pulses that are dictated by the electron bunch length, which can be orders of magnitude larger than the cooperation length.

8. Other Aims and Prerequisites • To lead the development of low charge single bunch diagnostics, synchronisation systems, advanced low level RF systems, and novel short period undulators. • To develop skills and expertise in the technology of NC RF photoinjectors and seed laser systems. • To develop novel techniques for the generation and control of bright electron bunches • manipulation by externally injected radiation fields • mitigation against unwanted short electron bunch effects (e.g. microbunching and CSR). • To demonstrate high temporal coherence and wavelength stability of the FEL, for example through the use of external seeding or other methods. • To develop the techniques for the generation of coherent higher harmonics of a seed source. • To develop new photon pulse diagnostic techniques as required for single shot characterisation and arrival time monitoring.

9. Fixing the Parameters ... • If we define... • Shortest wavelength • Longest wavelength • Minimum undulator gap • Minimum undulator parameter aw • ...this then defines the undulator period and required beam energy to tune over this wavelength range in a single undulator • Longest wavelength is at minimum gap and shortest wavelength is at maximum gap (min aw) • We know we might want resonant interactions with • Ti:Sa @ 800nm + harmonics • OPA at ~ 5um • HHG at 100nm – 50nm • So these are the wavelengths of interest... • Need to set energy/period to give us access to these wavelengths and some tunability across them

10. 1. Assume 8mm Gap, aw > 0.7 Tune from OPA at 5um to Ti:Sa at 800nm: 96MeV / 38mm At 100MeV, minimum wavelength is 370nm At 200MeV can just reach 100nm Tune between 3rd and 5th Harmonic of Ti:Sa: 170MeV / 24mm 5 4 5 1 2 3 4 1 2 1 3 4 5 3 2 Resonance with HHG at 100nm, no tunability: 190MeV / 19mm Resonance with HHG at 50nm, no tunability: 268MeV / 19mm Tune between 100nm and 50nm: 315MeV / 26mm

11. 2. More aggressive: 4mm gap, aw > 0.5 Tune from OPA at 5um to Ti:Sa at 800nm: 75MeV / 28mm At 100MeV, minimum wavelength is 185nm At 200MeV can reach 50nm Tune between 3rd and 5th Harmonic of Ti:Sa: 126MeV / 16mm 5 4 5 1 2 3 4 1 2 1 3 4 5 3 2 Resonance with HHG at 100nm, no tunability: 133MeV / 11mm Resonance with HHG at 50nm, no tunability: 189MeV / 11mm Tune between 100nm and 50nm: 237MeV / 17mm

12. Emittance Requirement 4

13. Genesis Modelling (SS) 250 MeV 100nm 60 keV energy spread 290A 1mm mrad

14. Preliminary Parameters • Beam Energy ~250 MeV • SASE Saturation length <15m • Seed with Ti:Sa 800nm, lase up to 8th harmonic • Seeding with HHG at 100nm also possible • Single spike SASE, electron bunch length ~50fs FWHM and charge <20 pC • Seeding, peak current ~400A, flat top ~300fs and charge <200 pC

15. Conceptual Layout

16. Cockcroft Institute ALICE & EMMA Light Source Test Facility

17. Possible Layout

18. Summary • The UK has the ambition to construct a next generation light source facility • The NLS CDR was published in 2010 • However, in the current financial climate this is unlikely to happen in the short term • We are planning to take advantage of this situation by building a next generation light source test facility that will ensure that the UK project (when funded) will be at the forefront in terms of output characteristics and underpinning technology • The full parameters are presently being discussed to ensure that the test facility has the flexibility we require

19. Acknowledgement • Thanks to Neil Thompson for the FEL parameter studies and Neil Bliss for the layouts