peter g. thirolf, lmu münchen the ‘fission–fusion‘ reaction mechanism: using dense...

Peter G. Thirolf, LMU München

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

for nuclear astrophysicsfor nuclear astrophysics

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

Peter G. Thirolf, LMU Munich

ELI-NP Workshop, Bucharest, March 10-12, 2011


r process: waiting point r process: waiting point N=126N=126

- waiting point N=126: bottleneck for nucleosynthesis of actinides- last region of r process ‘close’ to stability

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



- 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

Radiation Pressure AccelerationRadiation Pressure Acceleration

driver laser

ions electronsnmfoil

relativ. electrons at solid density

~ 1014 x density of conventionally accelerated ion beams



Exp. Scheme for “Fission-Exp. Scheme for “Fission-Fusion” Fusion”


~ 1 mm Fission fragments

Fusion products

Reaction targetProduction target

CD2: 520 nm

CH2 ~ 70 m

232Th: ~ 50m 232Th: 560 nm

APOLLON laser :

1.2.1023 W/cm2

32 fs, 273 J, 8.5 PW

1.0.1022 W/cm2

32 fs, 23 J, 0.7 PW

focus: ~ 3 m

232Th + p, C → FL + FH : beam-like fission fragments

beam (~ 7 MeV/u): d, C, 232Thtarget: p, C, 232Th

d, C + 232Th → FL + FH : target-like fission fragments

D. Habs, PT et al., Appl. Phys. B, in print


Fission Stage of Reaction Fission Stage of Reaction Scheme Scheme

232Th:<AL> ~ 91, AL ~ 14 amu (FWHM) AL ~ 22 amu (10%)<ZL> ~ 37.5 (Rb,Sr)

FL FH

fission mass distribution:


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


Collective Stopping Power Collective Stopping Power ReductionReduction

p

D

D

e

e

e

vk

ke

vm

vm

eZn

dx

dE

lnln4

2

2

2

42eff

binary collisionskD = Debye wave number

long-range collective interactionp = plasma frequency

Bethe-Bloch for individual ion:

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)

reduction of dE/dx : avoids ion deceleration below VC:

allows for thick reaction targets for fusion reactions



Exp. Scheme for “Fission-Exp. Scheme for “Fission-Fusion” Fusion”

collective stopping:


Fusion products

232Th: ~ 5 mm

CD2: 520 nm

232Th: 560 nm



APOLLON laser :

1.2.1023 W/cm2

32 fs, 273 J,8.5 PW

1.0.1022 W/cm2

32 fs, 23 J, 0.7 PW

focus: ~ 3 m

conventional stopping:


Fusion products


CD2: 520 nm CH2 ~ 70 m

232Th: ~ 50m 232Th: 560 nm

APOLLON laser :

1.2.1023 W/cm2

32 fs, 273 J, 8.5 PW

1.0.1022 W/cm2

32 fs, 23 J, 0.7 PW

focus: ~ 3 m


Fission-Fusion Yield / Laser Fission-Fusion Yield / Laser PulsePulse

laser acceleration (300 J, ~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



Towards N=126 Waiting Towards N=126 Waiting PointPoint

r process path: - known isotopes ~15 neutrons away from r process path (Z≈ 70)

0.5 0.1x

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 ?

- lifetime measurements: already with ~ 10 pps

measure: - masses, lifetimes, structure --delayed n emission prob. P,n

0.001fisfus

key nuclei



Experimental layoutExperimental layout

high powershort-pulselaser APOLLON

(gas-filled) separator

mirrortarget

concreteshielding

characterization of reaction products - decay spectroscopy

(tape) transport system

detector



Experimental layoutExperimental layout

high powershort-pulselaser APOLLON

(gas-filled) separator

mirrortarget

concreteshielding

gas stopping cellcooler/buncher

Penning trapmass measurements (m/m= 10-8)

characterization of reaction products - decay spectroscopy

precision mass measurements: e.g. Penning trap



““The Way Ahead”The Way Ahead”


exploratory experiments :

requirements:

- RPA target chamber - 232Th target development - ion diagnostics: Thomson parabola

- 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)


ConclusionsConclusions

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



Thanks to the Collaboration:Thanks to the Collaboration:

D. Habs (LMU, MPQ)T. Tajima (LMU, JAEA/Kyoto)J. Schreiber (LMU) M. Gross (LMU)A. 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 !Thank you for your attention !ELI-NP Workshop, Bucharest, March 10-12, 2011


Requirements for E1 @ ELI-NP:Requirements for E1 @ ELI-NP:Floorspace layoutFloorspace layout


production- separation area

measurement area

concrete shielding

18 m

12 m

12 m

15 m

recoil separator:- wide momentum acceptance- gas-filled ?


Experimental Requirements @ ELI-NPExperimental Requirements @ ELI-NP

110 m

12

0 m


E1:laser-induced nuclear reactions

“fission-fusion”

experimental areas

Laser clean rooms


Cost EstimateCost 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

peter g. thirolf, lmu münchen the ‘fission–fusion‘ reaction mechanism: using dense...

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