The LIBRA project: progress in source development and radiobiology applications

1. The LIBRA project: progress in source development and radiobiology applications M.Borghesi Centre for Plasma Physics, School of Mathematics and Physics The Queen’s University of Belfast Meeting on Laser-Plasma accelerators, Imperial College, 13 December 2012

2. Contributors S. Kar, D. Doria, R. Prasad, K.F. Kakolee, K. Quinn, B. Ramakrishna, G. Sarri, B. Qiao, M.Geissler, M. Zepf, Centre for Plasma Physics, Queen’s University Belfast, J.Kavanagh, G. Schettino, K. Prise, Centre for Cancer Research and Radiation Biology, Queen’s University Belfast D. Neely, D. Carroll, J. Green STFC-Rutherford Appleton Laboratory, P .McKenna, X. Yuan, University of Strathclyde, Z.Najmudin, N.Dover, C. Palmer, J Schreiber Imperial College, F. Fiorini, D.Kirby, S. Green, University of Birmingham, M. Merchant, C.J.Jeynes, K.Kirkby, University of Surrey, M. Cherchez, J. Osterholtz, O. Willi, Heinrich Heine University Dusseldorf, A. Macchi, University of Pisa

3. Laser Induced Beams of Radiation and their Applications Basic Technology programme, 2007-2012 Collaboration STFC Project aimed to develop target, detector and interaction technology required for high repetition, high energy operation of radiation sources. NPL LIBRA

4. Outline • Current properties of laser-ion beams • Proposed applications/requirements • Current research applications: • Radiobiology • Future applications: cancer therapy • Prospects for energy increase • Radiation Pressure Acceleration

5. Petawatt-class laser systems at the CLF, RAL VULCAN Energy : up to 500 J (on target) Wavelength : 1.05 m Pulse duration : 0.5 ps Intensity : ~1-5 1020 Wcm-2 Repetition : 8 to 10 shots / day GEMINI Laser, CLF, RAL: E ~ 12 J ,  = 0.8 µm,  = 50 fs Focal spot : 5 µm FWHM Intensity~ 1021 W/cm2 Rep rate : 1- 10 second

6. Sheath acceleration: ion beam properties • Low emittance: rms emittance < 0.01  mm-mrad • Short duration source: ~ 1 ps (Et < 10-6 eV-s) • High brightness: 1011 –1013 protons/ions in a single shot (> 3 MeV) • High current (if stripped of electrons): kA range • Divergent (~ 10s degrees) • Broad spectrum • Maximum energies: ~ 70 MeV • Scaling: E ~ (Il2) 0.5 Ion beam from TARANIS facility, QUB E ~10 J on target in 10 µm spot Intensity: ~1019 W/cm2, duration : 500 fs Target: Al foil 10um thickness

7. Prospective applications of laser-driven ion acceleration Applications already active with TNSA beams 150-250 MeV protons Carbon ions at 2-4 GeV Energies >GeV (high repetition)

8. What would ion beam users require ? • Wide energy and fluence range ✔ • Different ion species ✔ • Homogeneous transverse beam distribution ✔ • Stability in terms of energy/fluence distribution • Variable beam spot size • Beam control (diagnostic/dosimetry) within 5% error • High repetition Unique to laser-driven beams: Ultrashort particle burst duration (ps at sources) Ultrahigh dose rate (> 109Gy/s) Beamline approach (ELIMED beamline, Prague)

9. Charged particle therapy of cancer Compared to conventional x-ray radiotherapy: Ballistic advantages Biological advantages Large number of direct DNA damage. More effective in destroying radioresistanttumours (particularly with Carbon) Ions permit precise targeting of the tumor, minimizing the dose deposition in healthy tissues

10. Hadrontherapy centres worldwide are limited in number Only 3 facilities use Carbon ions • 8 in the USA • 6 in Japan • 12 in Europe/Russia • 3 in China, Korea, South Africa • 1 in UK ( Clatterbridge, limited to 60 MeV) 2 protontherapy trial centrescurrently being developed in the UK (active by 2017, UCLH London, Christie Hospital Manchester). Very high cost: >£ 100 M for protons, >£ 250 M for proton+Carbon Significant fraction of costs: transport/delivery systems (up to 50-70%) There is need for developing alternative approaches to hadrontherapy which may in future, help the treatment becoming more widespread / more efficient.

11. Laser-driven ions: a source for future radiotherapy? • Compared to conventional accelerators what do we need to improve? • - Narrow angular distribution • Narrow energy distribution (not simply slicing) • Beam purity • High repetition, stability • Higher endpoint energy • Reduced cost/shielding/size: • possibility to avoid/reduce size of gantry • laser transport rather than ion transport • (vast reduction in radiation shielded space) • Flexibility: • Possibility of controlling output energy and spectrum • Possibility of varying accelerated species • (H, C , but also intermediate species) • Novel therapeutic/diagnostic options • Mixed fields: x-ray + ions , multiple beams • In-situ diagnosis • High dose rates effects Several projects worldwide: SAPHIR (France) FDZ Dresden/ MPQ (Germany) ELIMED (Cz) Fox Chase Centre (USA)

12. Radiobiology experiments • We carried out tests of biological effectiveness of • laser-driven ions on V79 cells by using the TARANIS laser at QUB • Main aims: • establish a protocol for proton irradiation compatible with a laser-plasma environment • establish a procedure for on-shot dosimetry • Demonstrate dose-dependent cell damage • on single exposure, high dose irradiations • test for any deviation from known results using conventional sources Chinese hamster (Cricetulus griseus) TARANIS proton spectrum Previous work: S. Yogoet al, APL, 98, 053701 (2011) S.D. Kraft et al, NJP, 12, 085003 (2010) Dose of ~ 1-10 Gy is delivered in several fractions Each fraction has a short duration – 10 ns But effective dose rate ~ Gy/s – Gy/min

13. Setup for cell irradiation S D D ~ 27 cm Focusing Parabola N Vacuum chamber Wall 0.9 T magnet Laser Beam Target Slit (500 µm) 1 cm 50 um Mylar window 1 cm Mylar window : 50 µm Dispersion: in 20mm from 3MeV to 10MeV Energy Res.: ~ 2 MeV energy overlapping (500um slit) Delivered dose @ 1-5MeV: ~ few Gy/shot Proton beam characteristics at cell plane

14. Cell Irradiation Protocol for clonogenic assay Chinese Hamster Cell culture Sample preparation Colony formation Cell Irradiation Post-irradiation processing Energy Shadows of the cell dots

15. D.Doriaet al, AIP Advances 2, 011209 (2012) Single shot survival curve! Cell damage investigated at ultrahigh dose rates(> 109Gy/s) RBE10 estimated at ~1.4 In line with “standard” results with V79 cells e.g. Folkard et al, (1996) – Same RBE with LET=17.8 Kev/µm SF comparable with literature data at similar dose and energy but longer pulses Higher dose/dose rates obtainable with beam colllimation, or low dispersion magnetic systems Future tests: DNA damage, higher LET ions, Effects of oxygen depletion

16. Enhanced options offered by access to CLF lasers (GEMINI experiment scheduled in summer 2013) High efficiency producton of H and C beams from ultrathin foils (e.g. 25 nm at 5 1020 W/cm2)

17. Ion energy increase: several emerging mechanisms are being explored (besides TNSA optimization) • Radiation pressure acceleration • Hole boring • Relativistic transparency/ • Break out afterburner C.A. Palmer et al, Phys. Rev. Lett, 106, 014801 (2011) A. Henig, et al, Phys. Rev. Lett. 103, 045002 (2009) D. Jung et al, Phys. Rev. Lett.,107, 115002 (2011) Shock acceleration Radiation pressure acceleration Light Sail D. Haberberger et al, Nat Phys, 8.95 (2012)

18. Z+ e- Radiation Pressure on thin foils - light sail T.Esirkepov, et al. Phys. Rev. Lett., 92, 175003 (2004) O.Klimo et al, Phys. Rev. ST, 11, 031301 (2008) APL Robinson et al, NJP, 10, 013021 (2009) A.Macchi, S. Veghini, F. Pegoraro, Phys. Rev. Lett. , 103, 085003 (2009) • Cyclical re-acceleration of ions • Narrow-band spectrum (whole-foil acceleration) • Fast scaling with intensity • Issues at present intensities • Competition with TNSA • Hot electron heating cause foil disassembly • (ultrathin foils are needed for moderate a0) Areal density Scaling decreases for relativistic ions : linear scaling with I for vi~ c

19. PIC investigations of Radiation Pressure Acceleration (Light Sail regime) 2D PIC ILLUMINATION code Condition for stability of Light Sail identified (smooth transition between hole boring and light-sail phase,GeV protons at > 1022 W/cm2) B. Qiao et al, Phys Rev Lett,102,145002 (2009) Generally unstable at lower intensities, but: 2-species targets lead to stabilized acceleration of lighter species already at ~1020 W/cm2. B. Qiao et al, Phys Rev. Lett., 105, 1555002 (2010) B.Qiao, et al, Phys. Plasmas, (2011)

20. LIBRA campaigns at the CLF, RAL VULCAN Petawatt Pulse duration ~ 750 fs Energy on target up to 200 J Intensity up to 3 x 1020W/cm2 • Scans made by varying : • Laser Intensity, polarisation • Target density, thickness

21. Typical feature from ultrathin foils: Co-moving ions of diff e/m Density profile at two different times S. Karet al, Phys. Rev. Lett, 109, 185006 (2012) 100nm Cu; Linear Pol; I = 3 x 1020 W/cm2 2D PIC, multilayer, multispecies 50nm Cu; Cirular Pol; I = 1.5 x 1020 W/cm2 Cu e/m = 1 e/m = 0.5 e/m = 0.42 C p Hybrid regime where RPA cohexists with TNSA No significant dependence on polarization Solid line: TP1 (laser axis) Dotted line: TP2 (13o off axis)

22. Scaling of carbon peak with Light sail parameter S. Kar et al, Phys. Rev. Lett, 109, 185006 (2012) Henig, PRL (2009) Energy of peak scales ~ Conversion efficiency into peak ~ 1%

23. Scaling highly promising for achieving high Ion energies Inset : PIC simulation scaled up from VULCAN data (2 X I, 1/2.5 target areal density) Increase Fluence, or, Decrease  450 fs @ 5x1019W/cm2 45 fs @ 5x1020 W/cm2 Red dots: 2D and 3D results from multispecies simulations of stable RPA taken from literature

24. Similar spectra and scaling in GEMINI results – (Similar intensities but shorter pulses) C - 25 nm GEMINI data : Laser parameters : 50 fs, 6 J , 1-5 10 20 W/cm2 Targets : Carbon (amorphous), density: 2g/cc, thickness: 10-100 nm PIC syms Only lightest species shows peaks – not bulk component Onset of target transparency for the thinnest targets?

25. Conclusions The LIBRA project: progress in source development and radiobiology applications • Some of present applications of laser-driven ions exploit unique and distinctive properties of laser-ion beams (short duration, low emittance, small source): • proton radiography/deflectometry, Warm dense matter studies • Real time material damage studies, Ultra-high dose rate radiobiology • Applications currently covered by conventional accelerators (e.g. cancer therapy) require a marked improvement of parameters for laser-drivers to be competitive: • Compactness Is a clear advantage, but improvements are required in terms of energy, flux, etc.., but also high-average power, towards a beamline approach. • Radiation Pressure Acceleration is emerging from experiments, and promising for future delivery of pulses at high flux and high energies (medical energies and beyond)

26. Orbital Rhabdomyosarcoma X-Rays Protons Courtesy T. Yock, N. Tarbell, J. Adams

27. Radiation pressure acceleration in the light sail mode: GeV energies at 1022 W/cm2 B. Qiao et al, Phys Rev Lett,102,145002 (2009) Unstable case A.P.L. Robinson et al, NJP (2009) 30 nc • Stable acceleration requires smooth transition • between “hole boring” phase and LS phase • RP in phase 1: 2I/c Χ (1-vb/c)/(1+vb/c) • RP in phase 2: 2I/c Χ (1-vi/c)/(1+vi/c) • Need to drive target quite “hard” to achieve a high • hole-boring velocity (vb~c) before transition 100 nc 5 1022 W/cm2 Unstable case Rayleigh Taylor instability F. Pegoraro, S.V. Bulanov PRL (2007) ILLUMINATION 2D PIC code (M. Geissler) ILLUMINATION PIC code (M. Geissler, QUB)

28. In multi-species targets the acceleration of the lighter species is inherently more stable B. Qiao et al, Phys Rev Lett , 105, 1555002 (2010) • Target: electron density ne0=200nc, thickness l0=8nm<ls C6+ and H+ : nic0=32.65 nc, nip0=4.1nc with nic0:nip0=8:1 I0 ~ 51019W/cm2, 40 laser cycles, l= 1 µm Electrons C6+ The C6+ layer has insufficient charge-balancing electrons- Coulomb explosion H+ the protonlayer moves ahead of the C6+ layer. Debunching of the electron layer - complete separation of the C6+ and proton layers. Strong electron leakage Proton layer is surrounded by an excess number of electrons--->Stable RPA!!