The ‘Fission–Fusion‘ Reaction Mechanism: Using dense laser-driven ion beams

1. The ‘Fission–Fusion‘ Reaction Mechanism: Using dense laser-driven ion beams for nuclear astrophysics Peter G. Thirolf, LMU Munich Outline: • motivation: nucleosynthesis of heavy elements •  r process path: waiting point N=126 • ultra-dense laser-accelerated ion beams •  novel reaction mechanism: fission-fusion • experimental requirements at ELI-NP ELI-NP Workshop, Bucharest, March 10-12, 2011

2. r process: waiting point N=126 • r process: • - path for heavy nuclei far in ‚terra incognita‘ • - astrophysical site(s) still unknown: • core collapse SN II, neutron star merger ? Au, Pt, Ir,Os - waiting point N=126: bottleneck for nucleosynthesis of actinides - last region of r process ‘close’ to stability ELI-NP Workshop, Bucharest, March 10-12, 2011

3. ions electrons driver laser Radiation Pressure Acceleration relativ. electrons at solid density nm foil • cold compression of electron sheet, followed by electron breakout • dipole field between electrons and ions • ions + electrons accelerated as neutral bunch (avoid Coulomb explosion) • - solid-state density: 1022 - 1023 e/cm3 • ‘classical’ bunches: 108 e/cm3  ~ 1014 x density of conventionally accelerated ion beams ELI-NP Workshop, Bucharest, March 10-12, 2011

4. Exp. Scheme for “Fission-Fusion” Production target Reaction target 232Th: 560 nm 232Th:~ 50mm 1.2.1023 W/cm2 32 fs, 273 J, 8.5 PW ~ 1 mm Fission fragments APOLLON laser : Fusion products focus: ~ 3 mm 1.0.1022 W/cm2 32 fs, 23 J, 0.7 PW CD2: 520 nm CH2~ 70 mm beam (~ 7 MeV/u): d, C, 232Th target: p, C, 232Th 232Th + p, C → FL + FH : beam-like fission fragments d, C + 232Th → FL + FH : target-like fission fragments D. Habs, PT et al., Appl. Phys. B, in print ELI-NP Workshop, Bucharest, March 10-12, 2011

5. FL FH Fission Stage of Reaction Scheme • fission mass distribution: 232Th: <AL> ~ 91, DAL ~ 14 amu (FWHM) DAL ~ 22 amu (10%) <ZL> ~ 37.5 (Rb,Sr) • fusion-evaporation calculations (PACE4): • (Z=35,A=102) + (Z=35, A=102): Elab= 270 MeV (E* = 65 MeV) • 190Yb (Z=70,N=126): 2.1 mb • 189Yb ( N=125): 15.8 mb • 188Yb ( N=124): 61.7 mb • 187Yb ( N=123): 55.6 mb ELI-NP Workshop, Bucharest, March 10-12, 2011

6. Collective Stopping Power Reduction • Bethe-Bloch for individual ion: long-range collective interaction wp= plasma frequency binarycollisions kD = Debye wave number • reduction of atomic stopping power for ultra-dense ion bunches: • - plasma wavelength (~ 5 nm) « bunch length (~560 nm): •  only binary collisions contribute • - „snowplough effect“: first layers of ion bunch remove electrons • of target foil • - predominant part of bunch: screened from electrons (ne reduced)  reductionofdE/dx : avoidsiondecelerationbelow VC:  allows for thick reaction targets for fusion reactions ELI-NP Workshop, Bucharest, March 10-12, 2011

7. Exp. Scheme for “Fission-Fusion” Production target Reaction target conventional stopping: 232Th: 560 nm 232Th:~ 50mm 1.2.1023 W/cm2 32 fs, 273 J, 8.5 PW ~ 1 mm Fission fragments APOLLON laser : Fusion products focus: ~ 3 mm 1.0.1022 W/cm2 32 fs, 23 J, 0.7 PW CH2~ 70 mm CD2: 520 nm collective stopping: Production target Reaction target 232Th: 560 nm 232Th: ~ 5 mm 1.2.1023 W/cm2 32 fs, 273 J,8.5 PW ~ 1 mm Fission fragments APOLLON laser : focus: ~ 3 mm Fusion products 1.0.1022 W/cm2 32 fs, 23 J, 0.7 PW CD2: 520 nm ELI-NP Workshop, Bucharest, March 10-12, 2011

8. Fission-Fusion Yield / Laser Pulse laser acceleration (300 J, e~10%): normal stopping reduced stopping 232Th 1.2 . 1011 1.2 . 1011 C 1.4 . 1011 1.4 . 1011 protons 2.8 . 1011 1.8 . 1011 beam-like light fragments 3.7 . 108 1.2 . 1011 target-like light fragments 3.2 . 106 1.2 . 1011 fusion probability 1.8 . 10-4 1.8 . 10-4 FL(beam) + FL (target) neutron-rich fusion products 1.5 4 . 104 (A≈ 180-190) • laser development in progress: • diode-pumped high-power lasers: increase of repetition rate expected ELI-NP Workshop, Bucharest, March 10-12, 2011

9. Towards N=126 Waiting Point • r process path: • - known isotopes ~15 neutrons away from r process path (Z≈ 70) 0.001 sfisfus • measure: • - masses, lifetimes, structure • - b-delayed n emission prob. Pn,n - lifetime measurements: already with ~ 10 pps • visions: • test predictions: r process • branch to long-lived (~ 109 a) • superheavies (Z≥110) •  search in nature ? • improve formation predictions • for U, Th • recycling of fission fragments • in (many) r process loops ? 0.1 x 0.5 key nuclei ELI-NP Workshop, Bucharest, March 10-12, 2011

10. Experimental layout • characterization of reaction products • - decay spectroscopy high power short-pulse laser APOLLON detector (tape) transport system mirror target concrete shielding (gas-filled) separator ELI-NP Workshop, Bucharest, March 10-12, 2011

11. Experimental layout • characterization of reaction products • - decay spectroscopy Penning trap mass measurements (Dm/m= 10-8) • precision mass measurements: • e.g. Penning trap high power short-pulse laser APOLLON gas stopping cell cooler/buncher mirror target concrete shielding (gas-filled) separator ELI-NP Workshop, Bucharest, March 10-12, 2011

12. “The Way Ahead” • exploratory experiments : - staged approach with tests of crucial ingredients at existing facilities prior to operation of ELI-NP  laser ion acceleration of Th ions  collective effects of dense ion bunches (range enhancement) • requirements: • - RPA target chamber • - 232Th target development • - ion diagnostics: Thomson parabola ELI-NP Workshop, Bucharest, March 10-12, 2011

13. Conclusions • novel laser ion acceleration (RPA): - generation of ultra-dense ion bunches - enables fission-fusion reaction mechanism •  fusion between 2 neutron-rich fission fragments • - reduction of electronic stopping ? • - may lead much closer towards N=126 r-process waiting point • ELI-NP: unique infrastructure • - superior to ‘conventional’ radioactive beam facilities • The Way Ahead: • - exploratory experiments at existing laser beams • (Thorium acceleration, collective range enhancement..) • - collaboration has to be formed ELI-NP Workshop, Bucharest, March 10-12, 2011

14. Thanks to the Collaboration: • D. Habs (LMU, MPQ) • T. Tajima (LMU, JAEA/Kyoto) • J. Schreiber (LMU) • M. Gross (LMU) • Henig (LMU) • D. Jung (LMU) • D. Kiefer (LMU) • G. Korn (MPQ) • F. Krausz (MPQ, LMU) • J. Meyer-ter-Vehn (MPQ) • H.-C. Wu (MPQ) • X.Q. Yan (MPQ, Univ. Beijing) • B. Hegelich (LANL, LMU) • V. Liechtenstein (Kurchatov Inst., Moscow) Thank you for your attention ! ELI-NP Workshop, Bucharest, March 10-12, 2011

15. Requirements for E1 @ ELI-NP: Floorspace layout 18 m production- separation area measurement area 12 m 12 m concrete shielding • recoil separator: • wide momentum acceptance • gas-filled ? 15 m ELI-NP Workshop, Bucharest, March 10-12, 2011

16. Experimental Requirements @ ELI-NP Laser clean rooms 120 m E1: laser-induced nuclear reactions  “fission-fusion” experimental areas 110 m ELI-NP Workshop, Bucharest, March 10-12, 2011

17. Cost Estimate • component cost estimate: • - laser target chamber: ~ 200 kEUR • recoil separator : ~ 5000 kEUR • tape station : ~ 150 kEUR • decay detectors : ~ 150 kEUR • buffer gas cell : ~ 300 kEUR • mass analyzer : ~ 300 kEUR • electronics, control, • data acquisition : ~ 200 kEUR total: ~ 6.3 MEUR ELI-NP Workshop, Bucharest, March 10-12, 2011