1. Plasma Wakefield Acceleration G. Xia Cockcroft Institute University of Manchester 124/03/2015Novel acceleration topical meeting

2. Outline Motivations Current status worldwide Plasma wakefield acceleration at CLARA Other research topics at CLARA Summary 224/03/2015Novel acceleration topical meeting

3. Long term future of High-Energy physics requires the need for new high-gradient technology----Stressed at the updated European Strategy Report for Particle Physics in 2013. Gradients from 1GeV/m to 100 GeV/m are possible from relativistic plasma waves. Why plasmas? 3Novel acceleration topical meeting24/03/2015

4. Why plasmas? 4 e.g. n p =10 18 cm -3, the accelerating field will be 100 GeV/m! 10 3 orders of magnitude higher than the fields in conventional accelerators ! Novel acceleration topical meeting24/03/2015

5. Current status worldwide (Laser wakefield accelerators -LWFA) 24/03/2015Novel acceleration topical meeting5 Short pulse laser laser guiding in plasma (3’D’ effect: diffraction, dephasing, depletion)

6. LWFA @ LBNL 6 E. Esarey Novel acceleration topical meeting24/03/2015

7. Novel acceleration topical meeting7 Recent results-LWFA W.P. Leemans et al., PRL 113, 245002 (2014)

8. 8 driving force: Space charge of drive beam displaces plasma electrons. restoring force: Plasma ions exert restoring force Space charge oscillations (Harmonic oscillator) + + + + + + + + + + + + ++ ++ + + + + + + + + + + + + + + - -- -- - - - - - - - -- - - - -- - - - - - - - - - - --- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - -- - - - - - - - - -- - - - - - - - - - - - - - - -- - - - ---- - - - - - - - --- - - - - - - - - - - - - - - - - -- - - - - - - - - - - electron beam +++++++++++ +++++++++++++++ +++++++++++++++ +++++++++++++++ - - - - - -- -- Ez 24/03/2015Novel acceleration topical meeting Plasma wakefield accelerators (PWFA)

9. PWFA - Energy doubling @ FFTB 9 Electron beam (beam energy 42 GeV, bunch length 50 fs, bunch charge 2.9 nC) Plasma (heat Li oven, length 85 cm, density 2.7e17 cm-3) Max. energy gain 43 GeV (85 cm column) = 52 GeV/m ! Energy spectrum of the electrons in the 35-100 GeV range as observed in plane 2 Blumenfeld et al., Nature 445 (2007) 741 Novel acceleration topical meeting24/03/2015

10. Recent results-PWFA 24/03/2015Novel acceleration topical meeting10 M. Litos et al., Nature 515, 92-95 (2014)

11. Proton-driven PWFA A. Caldwell et al, Nature Physics 5, 363 (2009). p+p+ e-e- 600 GeV e - beam ≤1% ΔE/E in ~500 plasma Drive beam: p + E=1 TeV, N p =10 11 σ r =0.43 mm, σ θ =0.03 mrad, σ z =100 μm, ΔE/E=10 % Witness beam: e - E 0 =10 GeV, N e =1.5x10 10 Plasma: Li + n p =6x10 14 cm -3 External magnetic field: Field gradient: 1000 T/m Magnet length: 0.7 m 11 Novel acceleration topical meeting24/03/2015

12. CERN AWAKE experiment 12Novel acceleration topical meeting24/03/2015

13. CERN AWAKE experiment Scientific goals 1.Demonstrate self-modulation effect of a long proton bunch and realize 1 GeV electron energy gain with a ~10 m plasma 2.Develop and test the diagnostic equipments for the first and later experiments 3.Benchmark data against simulation results 4.Provide inputs for future experiment for 100 GeV in 100 m plasma Inject 10-20 MeV electron beam Acceleration of electrons to multi- GeV energy range after the plasma exit. 13Novel acceleration topical meeting24/03/2015 Strong UK Involvement, CI, JAI, RAL, Universities…

14. Why PWFA at CLARA? Why it makes sense – Free space available close to CLARA beam line – Unique beam properties (low emittance, high charge, relativistic) – Diverse beam operation modes – Well developed beam diagnostic equipment for VELA and CLARA (deflecting cavities, longitudinal bunch length measurement, etc.) Possible contributions to advanced accelerator community – Two-bunch experiment for energy doubling of CLARA beam – High transformer ratio (laser shaping of the bunch density profile, hard-edge bunch for an efficient wakefield excitation) – Ultrashort pulse x-rays production from betatron radiation – Plasma lens focusing effect – Hybrid wakefield acceleration/plasma photocathode injector – The self-modulation effect for a long beam (same gamma as SPS beam) 24/03/2015Novel acceleration topical meeting14

15. Plasma acceleration research station (PARS) 24/03/2015Novel acceleration topical meeting15

16. PARS beam line at CLARA 1624/03/2015Novel acceleration topical meeting

17. PARS beam line design VELA PARS at CLARA (D. Angal-Kalinin) 24/03/2015Novel acceleration topical meeting17

18. The proposed dogleg beam line design using “–I “ transform between the dipoles using two FODO doublets keeps the transverse beam emittance blow up due to coherent synchrotron radiation within acceptable limits for 250 pC at 250 fsec bunch length and for 20 pC at 30 fsec. The possibility of using the additional take off line at lower angle (~6  ) from the 30  dipole for high energy diagnostics spectrometer or a seeding dogleg dipole is being investigated. The proposed beamline is contained within the CLARA shielding area with a transverse centre-to- centre offset of ~1.5m. Extract CLARA beam at full energy of 250 MeV Dipoles -6  Dipoles +6  PARS at CLARA 24/03/2015Novel acceleration topical meeting18

19. PARS at CLARA Compared to electron driven plasma wakefield experiments at ATF@BNL, FACET@SLAC, FLASH II @DESY, beam energy at CLARA is intermediate, easy to handle and less radiation. Many interesting topics will be investigated: Two-bunch experiment (crafting two bunches via laser or mask collimator, one for driving plasma wakefield, the other for sampling the wakefield); for demonstrating energy doubling of CLARA beam, the witness beam with low emittance and low energy spread; High transformer ratio study (beam density profile shaping by shaping the laser pulse), e.g. multi-bunches or hard-edge beam can be an ideal driver beam; Ultrashort X-ray pulse generation via betatron radiation; Self-modulation of a long electron bunch—provide inputs to CERN proton-driven PWFA experiment (AWAKE); As the electron injector for a laser-driven wakefield acceleration (combined with LWFA research). 1924/03/2015Novel acceleration topical meeting

20. CLARA beam parameters 20 CLARA CDR, July 2013 24/03/2015Novel acceleration topical meeting

21. CLARA PARS Project Work packages: Electron Beam Delivery (design, operation and optimization of electron beam to the PARS; dogleg, final focus, e - beam dump, laser beam dump)—design work partly done. Plasma Source (produce a 5-200 mm long discharge plasma source with diameter of ~1 mm, density of 10 14 -10 17 cm -3, plasma diagnostics, density and temperature)---funding secured, ongoing work. Beam Diagnostics (measurement of beam specifications before and after plasma, emittance, energy, beam size, bunch length, charge, etc. energy spectrometer, CTR, OTR, streak camera, ICT, etc.)---under study. Simulations (electron beam simulation, PIC simulation of interactions between plasma and beam, code benchmarking, benchmarking the simulation results against the experimental data, optimize beam and plasma parameters for next round of experiments etc.)---ongoing work. 24/03/2015Novel acceleration topical meeting21

22. Two-bunch acceleration 24/03/2015Novel acceleration topical meeting22

23. Two-bunch acceleration 24/03/2015Novel acceleration topical meeting23

24. Two-bunch acceleration 24/03/2015Novel acceleration topical meeting24

25. Plasma density scan 24/03/2015Novel acceleration topical meeting25

26. Plasma density scan 24/03/2015Novel acceleration topical meeting26

27. High transformer ratio 24/03/2015Novel acceleration topical meeting27 High efficient acceleration with shaped electron bunches – with a long rise time and a shorter fall time. Such bunches can produce wakes that have a high transformer ratio. (CERN Courier, Feb. 2011)

28. Self-modulation instability Long bunch gets modulation in the wakefield excited by itself (bunch head). Many ultra-short bunch slices (scale of a plasma wavelength) are produced and then excite the wakefield and add up coherently to a high amplitude (AWAKE experiment at CERN). CLARA beam has a similar gamma factor (gamma ~ 500) as SPS beam, many plasma-beam dynamics could be similar and could be tested here at PARS. 2824/03/2015Novel acceleration topical meeting electrons

29. The plasma can be used as undulator to produce high brightness, ultra-short, keV to MeV photon pulse via betatron radiation. 24/03/2015Novel acceleration topical meeting29 X-ray from betatron radiation

30. Discharge plasma source 24/03/2015Novel acceleration topical meeting30

31. Plasma source 24/03/2015Novel acceleration topical meeting31

32. CLARA front-end 24/03/2015Novel acceleration topical meeting32

33. CLARA front-end Bunch length: 75 μm, beam radius: 20 μm, beam energy: 30 MeV, bunch charge: 250 pC, plasma density: 3E15 /cm^3 24/03/2015Novel acceleration topical meeting33

34. Other research topics at PARS Some advanced beam dynamics issues can be investigated in this dedicated test bed as well, e.g. Coherent synchrotron radiation-CSR (THz radiation), microbunching instability and its countermeasures, etc. ----crucial to FEL operation Beam manipulation and emittance exchange (deflecting cavities + dipole magnets)----for novel FEL modes like EEHG Beam instrumentation R&D for ultra-short electron beam (Electro-optical sampling, Smith-Purcell radiation etc.) 3424/03/2015Novel acceleration topical meeting

35. Summary Plasma wakefield acceleration has made tremendous progress in the last decades. It may change the field dramatically. The Plasma Accelerator Research Station (PARS) at CLARA will provide an ideal platform to investigate the key issues in plasma-based accelerators. A high accelerating gradient can be achieved with the relativistic CLARA beam. For the two-bunch experiment, a trailing bunch can gain energy from the wakefield and preserve its low emittance and low energy spread and get energy doubled. Many other issues on the advanced beam dynamics, beam instrumentation R&D, hybrid wakefield accelerators etc. can be investigated at PARS as well. 3524/03/2015Novel acceleration topical meeting

36. Next step… Funding application-STFC PRD grant, or EPSRC grant, £500k (beam lines, plasma source, beam and plasma diagnostics) Some dedicated ASTeC staff’s contribution to beam lines and diagnostics One PhD (T. Pacey) has been secured at the moment, he will concentrate on the CLARA PWFA experiment (plasma source + diagnostics) A dedicated PDRA will be needed to focus on this project (theoretical, simulation and experimental aspects) Collaboration with ASTeC, other CI Universities (including Strathclyde), Oxford and Imperial College London 24/03/2015Novel acceleration topical meeting36

37. 24/03/2015Novel acceleration topical meeting37 Acknowledgements ASTeC colleagues: J. Clarke, D. Angal-Kalinin, J. Jones, P.H. Williams, J.W. Mckenzie, B.L. Militsyn… Our team in Manchester O. Mete, H. Kieran, T. Pacey, Y. Li, M. Wigram, M. Dover, J. Zhang, J. Wright, G. Xia Tech-X UK J. Smith

38. 24/03/2015Novel acceleration topical meeting38 Thank you very much !