1. FEL R&D goals and potential in UK Institutes Brian McNeil, Department of Physics, University of Strathclyde For: Peter Ratoff, Director, Cockcroft Institute, Daresbury Laboratory

2. UK-XFEL R&D goals Critically examine potential FEL output performance enhancements over current generation of X-ray FELs. a)Achieving the best FEL output stability shot to shot (intensity and wavelength). b)Generation of flexible FEL output pulse structures (eg two colour, two pulse, …). c)Generating ultra-short photon pulses (sub fs). d)Generating transform limited FEL output (time-bandwidth product). Other potential enhancements (higher peak power, generating useful high harmonics of fundamental, polarisation control, …). We now want: Unique X-Ray output (for a while)

3. Preparing a suitable e - beam for the FEL interaction

4. Beam dynamics, beam diagnostic methods and tuning techniques. Lead academic: Andy Wolski, University of Liverpool Include space charge and wakefield effects, and general issues associated with the transport and manipulation of high-quality beams (such as the effects of multipole fringe fields) doi:10.1016/j.nima.2011.04.002 doi:10.1016/j.nima.2014.03.050 doi:10.1016/j.nima.2013.05.004 http://dx.doi.org/10.1088/1748-0221/7/04/P04016 VELA experimental results: Horizontal and vertical emittance asymmetry Coupling evident in the "tilt" of the beam distribution in the cross-plane phase space sections py-x and px-y

5. Experience to inform linac choices

6.  Common goals and issues to Superconducting (SC) & Normal Conducting (NC) Machines: -Preservation of Beam Quality (Emittance) -Machine Reliability and Stability, -Machine Cost (construction and Operational)  Superconducting (CW, short bunch) -Capitalize on expertise on 1.3 GHz/3.9 GHz ILC/XFEL/FLASH Beam Dynamics + HOM R&D (R.M. Jones et al) -Moderate Accelerating Gradients (30 - 40 MV/m) -Ongoing HOM Diagnostics at XFEL  Normal Conducting (Pulsed, Short Bunch) -Compare salient advantages and shortcomings of S, C, X-band options -Capitalize on CLIC/NLC Expertise (R.M. Jones et al) -Investigate Devlopments in the Availabilty of RF Sources -Potential for High Rep Rate (100 -1000 Hz) -Implications of Wakefields on Tolerances and Bunch Shaping -High Gradients (~100 MV/m) => Shorter Linacs -Leading Personnel: R.M. Jones (CI/Uman), A. Wheelhouse (ASTeC) Normal Conducting and Superconducting FEL Machine R&D Challenges and Goals Lead Academic: Roger Jones, University of Manchester

7. NC High Gradient CLIC Cavities Developed at CI/Univ. Manchester  Damped and Detuned Structure (DDS) with moderate damping Q~1000  Well-Suppressed Wakefield with 24 x Less Loads - remotely located  Prototype Built and Cold Tested –Excellent RF Characteristics  Next Stage –High Power/High Gradient Test Wakefield Transmission Cold Test of Completed Prototype DDS CAD of DDS Prototype Overview of CLIC  Requires More Than 71,000 Accelerating Structures Per Linac Single Cells Diamond Pt Machined

8. P1 C1 P3F P4 P2 C1 P7F P5 P6 P8 C3 P10FP9 C4 P13F P11 P12 P14 C5 P16F P15 C6 P19F P17 P18 P20 C7 P22F P21 C8 P25F P23 P24 P26 Higher Order Modes (HOMs) excited by passing bunch in accelerating cavity, are coupled out using HOM couplers. The HOM signals can be used to calculate beam position, angle, and arrival phase. Acting as a built in diagnostics, it can used to optimize beam trajectory, and parameters during operation, and to align cavities. SC Cavity FLASH/XFEL SRF HOM Diagnostics Developed at Cockcroft/Univ. of Manchester Bunch arrival phase + + x8 Generalized Scattering Matrix (GSM) code developed to characterize 8-cavity module Vast increase in speed and minimised memory requirements –obviates need for HPC Kick factors, and eigenmodes of overcoupled systems rapidly characterized Essential for HOM-based diagnostics Electronics Bunch Position HOM coupler Time Domain Radiation to HOM Ports Multi-Cavity HOM Transmission NAMES X

9. Carsten Welsch: “…interested in beam dynamics (transport and error) studies, multi colour and short pulse schemes, as well as in specialized beam diagnostics. …contribute to the definition of optimized (high resolution) longitudinal/transverse beam profile, emittance and possibly tomography monitors.”

10. Our ideas to push the FEL interaction towards the theoretical limits +

11. Electron-light phase shifting: π-shift Use chicanes to delay electrons c c c c

12. 12 *McNeil, Robb, Poole & Thompson, PRL 96, 084801 (2006) Schneidmiller & Yurkov, PRST-AB 15, 080702 (2012) Penn, PRST-AB 18, 060703 (2015) Harmonic Lasing in a FEL Seeded at fundamental DESY LBNL

13. X-ray FEL amplifier with mode-locking* Spike FWHM ~ 23 as *Thompson, McNeil, PRL 100, 203901 (2008) Kur, Dunning, McNeil, Wurtele & Zholents, NJP 13, 063012 (2011) Electron energy modulation at mode spacing LBNL

14. Few-cycle hard X-rays pulses* *Dunning, McNeil & Thompson, Phys. Rev. Lett. 110, 104801 (2013) Can generate few-cycle pulses – this takes x-ray FELs into the zeptosecond regime (10 -21 s) Extending to shorter wavelengths ( ≈ 0.2Å) few-cycle pulse durations ≈ 150 zs are predicted – entering the timescale of nuclear processes.

15. SASE: HB-SASE: 15 High Brightness-SASE * Thompson, Dunning & McNeil, TUPE050, Proceedings of IPAC’10, Kyoto, Japan *McNeil, Thompson and Dunning, Phys. Rev. Lett., 110, 134802 (2013) Poor temporal coherence Excellent temporal coherence SLAC- iSASE

16. SwissFEL

17. SLAC * *

18. “So, let’s build a completely new, improved UK-XFEL source: X-Ray, short pulses….” Maybe I should have practised this a little first!

19. We should have a FEL test facility Start as a R&D FEL test facility investigating the novel methods for short pulses etc. This can develop towards prototyping different elements of a UK-XFEL design. Already started on VELA gun, 400MHz C-band.

20. CLARA – a new UK test facility? 20 [Compact Linear Accelerator for Research and Applications]

21. What will CLARA look like? ELECTRONS GENERATED HERE ELECTRONS ACCELERATED AND MANIPULATED INTERACTIONS WITH LASER BEAMS FEL OUTPUT GENERATED FEL OUTPUT STUDIED PLASMA TEST LINE Total length about 90m Electron energy 250 MeV Fundamental wavelengths: 100nm - 400nm (ultra violet to violet)

22. The need for simulation First generation XFELs (LCLS, SACLA, EU-XFEL) can be modelled relatively simply with theortical estimates of performance ~10% of experimental reality. Most novel methods (Mode-Locking, Multi-Colour, ‘Beam-by-Design’) cannot. They rely upon non-linear processes and complex beam manipulation not easily described using theory. Require relatively complex computer simulation. It is a ‘Data Intensive Science’ requiring HPC such as that provided at The Harwell Centre. Summary: HPC resources are required for the design of a UK-XFEL incorporating novel output

23. Futue XFEL (FXFEL) simulator EPSRC ‘Software for the Future’ grant (EP/M011607/1) PI: Brian McNeil; CoI: Lawrence Campbell Partners:

24. ASTRAelegantVSim Analysis & visualisation essentials PUFFIN SDDS processing sdds2hdf hdf2vizschema Visit Common electron data set in SI units Common electron + field data set in SI units

26. Cannot be modelled using conventional FEL simulators

29. Conclusions  We can design a UK-XFEL that would generate unique X-Ray output allowing transformational new science to be carried out in the UK.  We need: To test, prototype and optimise the ideas and enabling technology on a FEL test facility – CLARA HPC resources required for an optimum UK-XFEL design. This cannot be done on workstations!  Other facilities are aware of the new methods – Can we do it before them and reap the scientific rewards?

30. Thank you!