FEL R&D goals and potential in UK Institutes

Transcription

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, ).

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) 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 doi: /j.nima doi: /j.nima doi: /j.nima

5 Experience to inform linac choices

6 Normal Conducting and Superconducting FEL Machine R&D Challenges and Goals Lead Academic: Roger Jones, University of Manchester 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 ( 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)

7 NC High Gradient CLIC Cavities Developed at CI/Univ. Manchester S-Parameter (db) 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 Overview of CLIC Requires More Than 71,000 Accelerating Structures Per Linac CAD of DDS Prototype Wakefield Single Cells Diamond Pt Machined /2 (S 11 +S 31 +S 13 +S 33 ): Measurement -40 HFSS scaled in Air ( = ) r Frequency (GHz) Transmission Cold Test of Completed Prototype DDS

8 P4 SC Cavity FLASH/XFEL SRF HOM Diagnostics Developed at Cockcroft/Univ. of Manchester P26 Higher Order Modes (HOMs) excited by passing bunch in accelerating cavity, are coupled out using HOM couplers. X 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. Bunch arrival phase 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 HOM coupler Time Domain Radiation to HOM Ports Bunch Position Multi-Cavity HOM Transmission Electronics NAMES x8 + + P1 C1 P7F C1 P6 P8 C3 P13F C4 P12 P14 C5 P19F C6 P18 P20 C7 P25F C8 P24 P3F P2 P5 P10F P9 P11 P16F P15 P17 P22F P21 P23

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: c c π-shift c c Use chicanes to delay electrons

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

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

14 Few-cycle hard X-rays pulses* 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. *Dunning, McNeil & Thompson, Phys. Rev. Lett. 110, (2013)

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

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? [Compact Linear Accelerator for Research and Applications] 20

21 What will CLARA look like? Electron energy 250 MeV Fundamental wavelengths: 100nm - 400nm (ultra violet to violet) FEL OUTPUT STUDIED Total length about 90m

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 Analysis & visualisation essentials ASTRA elegant VSim PUFFIN SDDS processing SDDS processing SDDS processing SDDS processing Common electron data set in SI units sdds2hdf hdf2vizschema Visit Common electron + field data set in SI units

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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!