WG-6 Laser-Plasma Acceleration of Ions

1. WG-6 Laser-Plasma Acceleration of Ions Leader: Sergei Tochitsky, UCLA Co-leader: Manuel Hegeleich, LANL AAC-2012, Austin

2. Goals: Ion Beam with a narrow energy spread Energy Frontier ≥200 MeV protons ≥1 GeV MeV ions High-Rate Reproducible Ion source

3. Main Laser Plasma Acceleration Mechanisms • RPA • (bulk/volume) • TNSA • (surface) • BOA • (bulk/volume) • SWA • (bulk/volume) LASER Shock reflected Ions e- ions Challenges & Boundary conditions Results Experimental & PIC Ion beam Characteristics LA-UR-12-22090

4. Ion acceleration mechanisms in solid targets Difficulty Acceleration mechanism TNSA (surface) BOA (bulk/volume) RPA (bulk/volume) Requirements IL>1018 W/cm2 IL>5x1019 W/cm ~100 nm Ultra-high contrast (>108) IL>1020-1022 W/cm2 1-50 nm Ultra-high contrast (>108) 1D geometry 1-100 micron Targets Ion beam Characteristics All species Emax>100 MeV/amu, CE ~ 10% Typically exp. decaying All species Emax* >1 GeV/amu, CE* 10% Monoenergetic distribution* *Prediction Highest q/m (H+) Emax~60 MeV CE ~ 1-10% Typically exp. decaying LA-UR-12-22090

5. 40 MeV proton generation by 7.5 J 200TWlaser pulse interaction with robust SUS 2 mm targetkTe confirms 2x1021 Wcm-2 laser intensity on target 60° Strong charge separation regime OAP F=2.14 ＋5.2° 〜9.3 MeV Laser pulse 8 J , 40fs, contrast level 1x1010 Proton Estimated Emax =54MeV 30° Electron spectrum 20° FWHM~40fs 5° FWHM 4x3 mm2 1.6x1021 Wcm-2 +10.3° kTe ~ 16MeV ＋11.3° +10.3° 37.2〜38.9 MeV 25.5〜27.5 MeV 38.9〜40.5 MeV Ogura, Nishiuchi, Pirozhkov et al. 2012 Opt. Let.

6. From TNSA towardsthe RPA regime • JETI40 withplasmamirror: • 15 nmParylene (C8H6F2) revealsprotonpeaksbetween 1…2.1 MeV on top ofexponentialbackground • POLARIS laser: • TNSA study on target material andthickness • complexinterplaybetweentargetandlaserparametersturned out Ta(Z=73) Ag(Z=47) Cu(Z=29) Ti(Z=22) Proton cutoff energy [MeV] • supportedbynumerical 2D PIC simulations Al(Z=13) Target thickness [µm] 6

7. Simulations show a competition between two parameters. M. Carrié et al. Phys. Of Plasma, 16, 053105 (2009). Laser-plasma coupling: Absorption and electron-temperature. Exα λd0/lss*(nhot*Thot)1/2 T. Grismayer et P. Mora. Phys. Plasmas 13, 032103 (2006). Plasma gradient: Increases with time because of target expansion. 2D simulations using the PIC code CALDER.

8. Efficient proton acceleration during intra-pulse phase • Proton beam deflection at oblique incidence • Most energetic protons are deflected in experiment • History of most energetic protons from 2D PIC simulation overlaid • Protons initially emitted under optimal angle • Injection into expanding sheath • Test experiment with tilted pulse front • Prominent non-target-normal proton beam emission • Spatiotemporal asymmetry restricted to coherent short pulse • Proton deflection as signature of the promptly accelerated electrons • Efficient proton acceleration during intra-pulse phase prior to the plasma expansion (pre-thermal) Zeil et al. Nature Communications 6:874 (2012)

9. High Energy, High Quality TNSA Beams From Microcones and Limited Mass Targets Trident 75 MeV from LMT Preplasma from high contrast (>10-10 ASE) Trident “main sequence” follows I1/2 Constant energy Constant spot size M. Schollmeier et al. in prep (2012) 67 MeV from Cones t = -7ps Laser contrast Blue and green correspond to lineouts above High Quality Beams 108 Cu Ka 2D transverse image -5 K. A. Flippoet al. J. Phys.: Conf. Series244 022033 (2010) S. Gaillard et al., Physics of Plasmas18, 056710 (2011)

10. 24MeV Proton Bunches Using Microstructured Snow Targets Irradiated by 5TW LaserHebrew University/MBI/NRL • Microstructured Snow Targets are providing: High laser-target coupling (95%); Easy to manufacture and control; Debris free ; Reduce demands on pre-pulse high contrast ratio; Geometrical features that enhance acceleration • 24 MeV protons were measured during the interaction of a 5TW laser with micro-structured snow target CR-39 Stack Laser Thompson Parabola Protons Snow Landscape Snow target

11. Front curvature - Heating Mechanism • Finite Spot effects strongly influence heating • Target deformation increases with decreasing target thickness Electron Density Electron Density Thin Electron Density Thick

12. Stable RPA with two-component target a0~5 V. Hudik, UT • intensity dependant optimum • low divergence (140mrad) • containing ~6.5% of the laser energy (0.5% H+) • RT signatures appearing at highest intensity & thinnest target • l = 25 nm target • circular laser polarization • average of 4 consecutive shots • creation of a stable ion-ion interface at 2MeV/amu Formvar(mass: C:H~ 5:1) ~25nm (35fs), ~13nm (70fs) Target Results I Results II

13. Igor Pogorelsky, BNL “Optical probing of laser hole-boring into overdense plasma” ne ncr laser Vsh 2Vsh 2V V 0 • 5% energy spread • 5x106 protons within 5-mrad • spectral brightness 7×1011 protons/MeV/sr jet foil

14. Exceeding 100MeV/amu with BOA with a 150 TW laser • >1GeV C6+ from Diamond target (measured on CR39 and Stack) • Increased carbon C6+ energies to over 1GeV • Increased maximum energy by a factor of 20 over previous results achieved with TNSA • >100MeV H+ from CH2 target (measured on IP and CR39-Stack) • Increased proton energies to over 100MeV • Increased maximum energy by a factor of 2 over previous results achieved with TNSA/BOA CR39 Stack LA-UR-12-22090

15. Up to 8 Gray in a single 1 ns proton bunch, 1.3 m from target • Combination of all “cutting edge” methods for an application • PM + nm targets (high particle numbers, low secondary radiation) • Compact setup with PM-QPs (setup could be smaller than 50 cm) • low laser energy (400 mJ, in principle 10 Hz operatable) • truly ns-biology (single shot high dose) • E = 5.5 MeV, DE/E=6% cells 1 cm Courtesy of Dan Keifer

16. G. Turchetti et al University of Bologna Transport and post acceleration The LILIA experiment at LASERLAB Frascati (Rome) is devoted to prove Injection at 30 MeV of a TNSA proton beam into a compact linac ACLIP Phase 1: I=1020 a=8 diagnostics and targets tests (2012) Phase 2: I=2 1021 a=30 injection and post acceleration 3D PIC simulations with PIC codes AlaDyn and Jasmine (GPU) with composite targets (foil+foam layer) give more than 108 protons at E=30 MeV DE=0.5 MeV Energy selection with solenoid and collimators allows to post-acc ~ 107 protons First module of ACLIP

17. UCLA Shock Wave Acceleration in gas jet 10µm Laser – Gas Jet Gas plume Emax ~a03/2 F. Fiuza SWA scaling (submitted PRL) Extended Plasma hybrid PIC E TNSA ~ 1/L

18. 100 μm Strong shockwave generation M. Helle, D. Gordon, D. Kaganovich and A. Ting Gas Flow 10 TW Laser Shock Front 50 μm Shockwave Laser Gas Jet w/ Block • A block placed within the gas jet aids in coupling laser energy into shock. • A sharp gradients produced by this shock has been seen in experiments and simulations preformed using the hydrodynamics code SPARC. • Experiments show density gradients <50 um and peak density >1020 cm-3 *D. Kaganovich, M.H. Helle, D.F. Gordon, and A. Ting, Phys. Plasmas 18, 120701 (2011)

19. Laser ion acceleration with low density targetsE. d’Humières, S. Bochkarev and V.T. TikhonchukUniv. Bordeaux - Lebedev Institute (Russia) • Efficient underdense laser proton acceleration is possible for various laser and target conditions. Depends strongly on the laser pulse shape. First experimental validation at LULI (few MeV protons with 500 nm exploded foils and few J of laser energy). First high laser energy experiments at Titan/LLNL this summer • The shock regime can be very efficient and offers an interesting alternative to overdense ion acceleration schemes. Modeled using 2D and 3D PIC simulations and a Boltzmann-Vlasov-Poisson Difficult to use gas jets with nowadays nozzle technology but exploded foils could help to highlight this mechanism experimentally. • Accelerated proton beam characteristics are similar to the ones obtained using solid targets. The ratio of maximum proton energy over laser energy is even higher for low density targets (when interaction is optimized in both cases). High laser energy and intensity allow to explore high density/thickness couples and lead to very energetic ions. • Requires high laser energies and long gradients to efficiently reflect ions with the targets available today.

20. UCLA Laser-Driven Ion Beams:applications

21. Laser-Plasma Potential Applications • >50 MeV high-brightness injector for a large RF accelerator. • ~200 MeV/u Plasma accelerator for hadron therapy. • 5-10 MeV ion source at 1-10 Hz (for example for F18 Medical isotopes for PET). • Neutron source driven by LDIA, very short neutron pulses for material science. • Very high peak current ion beams for R & D. :WDM, Fast Ignition, etc.

22. Pulsed Neutron Source 10 mm Cu with D20 ice coating X-Ray & Neutron Generation • d p d 0224_2012_shot#4 A. Maksimchuk, UM Experiment at Trident 20-40 MeV Deuterons 1010-1011 Neutrons/shot M. Roth, DTU

23. Status: Where we are in 2012 LANL >100 MeV from a nanofoil, LANL UCLA, Neptune Lab JAEA 22 MeV protons with a narrow Energy spread from H2 gas jet plasma UCLA 40 MeV protons from a TNSA Japan -K. Zeil et. al., New J. Phys 12, 045015 (2010) AAC-2012, Austin