Laser plasma wakefield acceleration and ICAN

Transcription

1 Laser plasma wakefield acceleration and ICAN Laura Corner John Adams Institute, University of Oxford Special thanks to S.M. Hooker ICAN workshop, Paris, April 28 th 2014

2 Outline The basic idea. Experimental results. What does ICAN bring? Future plans. Simulation: Cameron Geddes, LBNL Visualization: Peter Messmer, Tech-X Corp.

3 The basic idea The ponderomotive force in a laser pulse with intensity ~ W cm -2 expels electrons from the region of the pulse to form a trailing plasma wakefield (laser wakefield acceleration LWFA). In a conventional particle accelerator the gradient is limited by electrical breakdown to: A plasma accelerator can reach gradients of order: Smaller (cheaper!) accelerators.

4 Early results Z. Najmudin et al. Phys. Plasma (2003) S. D. Mangles et al. Nature (2004) Early experiments on laser-driven plasma accelerators show continuous, quasithermal energy spectrum. Electrons injected from background plasma. Maximum electron energy ~ 100 MeV. Laser parameters Energy: 1 J Pulse duration: 30 fs

5 The first quasi-monoenergetic beams Typical output parameters: Output energy: MeV Energy spread: 2.5-8% Bunch charge: pc Plasma parameters: Plasma density of ~ cm -3 Length of gas jet ~ 1-2 mm C. G. R. Geddes et al. Nature (2004) S. D. Mangles et al. Nature (2004) J. Faure et al. Nature (2004)

6 Gas-filled capillary discharge waveguide Mechanisms responsible for channel formation described in detail in: N. A. Bobrova et al. Phys. Rev. E (2002) B. H. P. Broks et al. Phys. Rev. E (2005) B. H. P. Broks et al. J. Phys. D (2006) B. H. P. Broks et al. Phys. Plasm (2007) Plasma channel formed by heat conduction to capillary wall. Channel is fully ionized and stable.

7 Guiding in 33mm long channels W. P. Leemans et al. Nature Physics (2006) K. Nakamura et al. Phys. Plasmas (2007) no capillary with capillary laser beam profile in capillary exit plane Laser pulse energy approx. 100 mj Entrance Exit Capillary 190 um Input laser power 40 TW Input intensity > W cm -2 Plasma: cm -3 Spot size at entrance 26 μm Spot size at exit 33 μm

8 Generation of 1 GeV electron beams W. P. Leemans et al. Nature Physics (2006) K. Nakamura et al. Phys. Plasmas (2007) Experiment conditions: Capillary: 33 mm, 312 μm diam. Density cm -3 Laser: 40 TW: 1.5 J, 37 fs E = (1.0 +/- 0.06) GeV ΔE = 2.5% r.m.s Δθ = 1.6 mrad r.m.s. Q = 30 pc

9 Recent high energy results Recent rapid progress in electron energy: 2 GeV : Wang et. al. Nature Commun (2013) 100J, 150fs, shot/hr. 3 GeV : Kim et. al. PRL 111, (2013) 2 stage accelerator, 25J, 60fs, 0.1Hz. 4.2 GeV : Leemans et. al. reported at NPAC (2013) 15J, 40fs, 1Hz. This progress driven by better technology: Gas stage design Capillary design Clever experiment But mainly the lasers! So the lesson is that to fundamentally change LWFA need to fundamentally change the laser driver.

10 An ideal laser? What would we like? High energy 10s J. Laser? Short pulse 10s fs. High rep. rate 10s khz. High efficiency 10s %. Good contrast - > 10 12? Good spatial quality M 2 ~ 1. Low maintenance & running costs. Not impossibly expensive. An ideal laser? Oh, I don t think I should like that. It sounds like something out of the next world. Oscar Wilde (paraphrased)

11 What does ICAN offer for LWFA? Rep rate! From shots / hour or few Hz to khz complete paradigm shift for experiments. Enhanced statistics. Fully explore parameter space. Confirm (or not) theoretical predictions. Realistic applications for imaging etc. Exciting applications for driving FEL. Courtesy Stefan Karsh et al. MPQ

12 Future plans Any demonstration of accelerated electrons > 1 khz major game changer. High energy desirable but not necessarily essential. Produce prototype laser and run high rep. rate demonstration experiment? ~1 J, few 100 fs, > 1 khz? Need facility development in parallel with laser development though: Target/diagnostic development for khz rates very important. High average power handling issues? Requires co-ordinated approach between several groups to develop experimental technology while prototype laser being built.

13 Summary Laser-driven plasma accelerators have made significant advances in last few years very exciting recent results. Now possible to generate monoenergetic electron beams with energies comparable to those used in synchrotrons. The first applications are being investigated incoherent sources of tunable, femtosecond x-rays very compact FELs? THz generation for security applications? But applications limited by properties of laser drivers rep. rate, expense, efficiency. ICAN project could revolutionise progress in LWFA. Requires combined approach to design suitable experiment in parallel with laser.

14 Thanks to... S. Bajlekov, N. Bourgeois, L. S. Caballero, J. Cowley, S. Dann, G. Doucas, T. Ibbotson, W. Rittershofer, T. Rowlands-Rees, A. Seryi, P. A. Walker, R. Walczak. E. Esarey, C. G. R. Geddes, A. J. Gonsalves, B. Nagler, K. Nakamura, C. B. Schroeder, Cs. To th, W. P. Leemans et al. M. Fuchs, F. Grüner, D. Habs, S. Karsch, Zs. Major, J. Osterhoff, A. Popp, U. Schramm, G. D. Tsakiris, R. Weingartner, B. Zeitler, F. Krausz et al. C. Kamperidis, S. Kneip, S. P. D. Mangles, S. R. Nagel, C. Palmer & Z. Najmudin et al. O. Chekhlov, R. Clarke, E. Divall, K. Ertel, S. J. Hawkes, C. J. Hooker, C. Murphy, B. Parry, P. Rajeev, R. Trines, P. Foster, D. Symes, M. Streeter & P.A. Norreys. EPSRC, STFC, EU (EuroLEAP), Leverhulme Trust, the MathWorks for financial support.