Plasma Wakefield Acceleration G Xia Cockcroft Institute University

Plasma Wakefield Acceleration G. Xia Cockcroft Institute University of Manchester 24/03/2015 Novel acceleration topical meeting 1

Outline • • • Motivations Current status worldwide Plasma wakefield acceleration at CLARA Other research topics at CLARA Summary 24/03/2015 Novel acceleration topical meeting 2

Why plasmas? 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 1 Ge. V/m to 100 Ge. V/m are possible from relativistic plasma waves. 24/03/2015 Novel acceleration topical meeting 3

Why plasmas? e. g. np=1018 cm-3, the accelerating field will be 100 Ge. V/m! 103 orders of magnitude higher than the fields in conventional accelerators ! 24/03/2015 Novel acceleration topical meeting 4

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

LWFA @ LBNL 24/03/2015 Novel acceleration topical meeting E. Esarey 6

Recent results-LWFA W. P. Leemans et al. , PRL 113, 245002 (2014) 24/03/2015 Novel acceleration topical meeting 7

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

PWFA - Energy doubling @ FFTB Electron beam (beam energy 42 Ge. V, bunch length 50 fs, bunch charge 2. 9 n. C) Plasma (heat Li oven, length 85 cm, density 2. 7 e 17 cm-3) 35 -100 Ge. V range as observed in plane 2 Max. energy gain 43 Ge. V (85 cm column) = 52 Ge. V/m ! 24/03/2015 Energy spectrum of the electrons in the Blumenfeld et al. , Nature 445 (2007) 741 Novel acceleration topical meeting 9

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

Proton-driven PWFA Drive beam: p+ e- =1011 E=1 Te. V, Np σr=0. 43 mm, σθ=0. 03 mrad, σz=100 μm, ΔE/E=10 % Witness beam: e- p+ 600 Ge. V e- beam E 0=10 Ge. V, Ne=1. 5 x 1010 ≤ 1% ΔE/E in ~500 plasma Plasma: Li+ np=6 x 1014 cm-3 External magnetic field: Field gradient: 1000 T/m Magnet length: 0. 7 m 24/03/2015 A. Caldwell et al, Nature Physics 5, 363 (2009). Novel acceleration topical meeting 11

CERN AWAKE experiment 24/03/2015 Novel acceleration topical meeting 12

CERN AWAKE experiment • • Scientific goals Inject 10 -20 Me. V 1. Demonstrate self-modulation effect of a long proton bunch and realize 1 electron beam Ge. V electron energy gain with a ~10 m plasma Acceleration of 2. Develop and test the diagnostic equipments for the first and later electrons to multiexperiments Ge. V energy range 3. Benchmark data against simulation results after the plasma exit. 4. Provide inputs for future experiment for 100 Ge. V in 100 m plasma Strong UK Involvement, CI, JAI, RAL, Universities… 24/03/2015 Novel acceleration topical meeting 13

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) 24/03/2015 Novel acceleration topical meeting 14

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

PARS beam line at CLARA 24/03/2015 Novel acceleration topical meeting 16

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

Extract CLARA beam at full energy of 250 Me. V PARS at CLARA Dipoles -6 Dipoles +6 24/03/2015 • 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 p. C at 250 fsec bunch length and for 20 p. C 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-tocentre offset of ~1. 5 m. Novel acceleration topical meeting 18

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). 24/03/2015 Novel acceleration topical meeting 19

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

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 1014 -1017 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. 24/03/2015 Novel acceleration topical meeting 21

Two-bunch acceleration 24/03/2015 Novel acceleration topical meeting 22

Two-bunch acceleration 24/03/2015 Novel acceleration topical meeting 23

Two-bunch acceleration 24/03/2015 Novel acceleration topical meeting 24

Plasma density scan 24/03/2015 Novel acceleration topical meeting 25

Plasma density scan 24/03/2015 Novel acceleration topical meeting 26

High transformer ratio 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) 24/03/2015 Novel acceleration topical meeting 27

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. electrons 24/03/2015 Novel acceleration topical meeting 28

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

Discharge plasma source 24/03/2015 Novel acceleration topical meeting 30

Plasma source 24/03/2015 Novel acceleration topical meeting 31

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

CLARA front-end Bunch length: 75 μm, beam radius: 20 μm, beam energy: 30 Me. V, bunch charge: 250 p. C, plasma density: 3 E 15 /cm^3 24/03/2015 Novel acceleration topical meeting 33

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. ) 24/03/2015 Novel acceleration topical meeting 34

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. 24/03/2015 Novel acceleration topical meeting 35

Next step… • Funding application-STFC PRD grant, or EPSRC grant, £ 500 k (beam lines, plasma source, beam and plasma diagnostics) • Some dedicated ASTe. C staff’s contribution to beam lines and diagnostics • One Ph. D (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 ASTe. C, other CI Universities (including Strathclyde), Oxford and Imperial College London 24/03/2015 Novel acceleration topical meeting 36

Acknowledgements ASTe. C 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 24/03/2015 Novel acceleration topical meeting 37

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