Nuclear Physics with ELI, Population/depopulation of Isomers: modification of nuclear level lifetime F. Gobet, C. Plaisir, F. Hannachi, M. Tarisien, M.M.

Nuclear Physics with ELI, Population/depopulation of Isomers: modification of nuclear level lifetime

F. Gobet, C. Plaisir, F. Hannachi, M. Tarisien, M.M. Aléonard

CENBG, Université de Bordeaux, CNRS,IN2P3

V. Méot, G. Gosselin, P. Morel , CEA/SPN, Bruyères le Châtel

P. Audebert et al., LULI Polytechnique

Nuclear Physics with ELI

Great interest in a PW laser with a high repetition rate for Nuclear Physics:

Typically >1 Hz ( mbarn or sub-mbarn cross sections )

A facility to produce - high energy electrons, protons

- (dense and warm) plasma

- intense (E,B) field

Allowing several synchronous laser beams with modular temporal characteristics: 10 fs to ns(?)

1) create a (warm and dense) plasma

protons, electrons,photons

2) create a bunch of high energy particles

With a high power laser it is possible to :

E 1010 V/cm

B 1000 T

3) Excite nuclei (inside the plasma)

4) Submit these nuclei to high electromagnetic fields or second production particles

Other deexcitation modes of the nucleus may appear: T1/2

Resonant Internal Conversion on unoccupied bound states has been shown.

What we know: the effect of the ionization on the electronic shells:

Internal Conversion can be modified, eventually suppressed: T1/2

125mTe (first excited state at 35,49 keV) 52

ns49.121t

ns1121t 48+

Resonant Internal Conversion on occupied bound states is predicted in 187 Au (2) (experiment at GANIL)

(1) T. Carreyre et al, Phys. Rev.C 62 (2000), 024311

(2) F.F. Karpeshin et al. PRC 65, 034303 (2002)

(1)

neutral

e-

Can nuclear lifetime be modified in a plasma?

Can nuclear lifetime be modified in a plasma?

In a plasma excitation of intermediate states, can modifythe effective lifetime of a nuclear state

N.Klay et al. PRC 44,2839 (1991)10 keV

β-

(n,)β-

72

71

70

176Lu abundancecosmochronometry, cosmothermometry, and s-process branching

1) Petawatt laser to populate the isomer

2) laser (warm plasma) for isomer excitation

3) Observation

of a 251 keV

20’0.463 MeV

= 3.4 keV

9 ns

0.248 MeV E=248 keV

32.7 d

85Rb(,n)84mRbM1

84Rb

Enhanced deexcitation of isomers :the 84Rb isomer, a laboratory case similar to 176Lu

CENBG,LULI, CEA-DAM-DPTA, collaboration

85Rb(,n)84mRb: cross section just measured at the ELSA (19 MeV) electron facility (Bruyères le Châtel); analysis under process

Pumping the isomer state

Several processes are competing to the excitation of a nucleus in a plasma via photon absorption, inelastic scattering of electrons or via the electronic shell structure (NEET, NEEC…processes)

Hypothesis:

T° plasma ~ 2keV:

charge states >28 during t:10 ps – 1ns

Several 100 excited isomers (detection possible)

Experimental data for the theoretical models of nuclear excitations in plasma

plasma = 0,01g/cm3

(Gosselin et al; PRC 70 (2004) 064603 and PRC 76 (2007) 044611

Excitation rate of the 6- level in 84Rb as a function of the plasma charge state

Multilevel system: indirect deexcitation process or lifetime modification

• The 93Mom case:

G.Gosselin, V.Meot and P.Morel PRC 76 (2007) 044611

Lifetime: ~5 orders of magnitude decrease

93Nb(p,n)93Mom

0.2 keV

84Rb

Partial level scheme of 84Rb

Exc

itat

ion

en

erg

y

2 gammas to be detected

219.1 keV 248 keV

Long pulse large diameter (20 ns, =700 µm) to create plasma conditions after the Petawatt shot (up to a some minutes after Petawatt shot)

Or other excitations: e,e’, photoexcitation,… with another Petawatt laser

Al target

converter85 Rb

Electrons

Shielded ray detector

Petawatt:electron production laser

(50 fs, 10J, =20µm)

85Rb(n)84mRb

Absolute need : high repetition ratefor the 2 laser beams

Laser 1L

aser

2

High brightness for secondary particle sources: short pulse (10-100 fs) I > 1020 W/cm2

High repetition rate to overcome low cross sections: 1 Hz < rate < 1 kHz Large warm plasma long pulse (ns?): I~1014 W/cm2,

focal spot ~500 µm2

High electromagnetic fields

Great interest of lasers: they afford several synchronous beams to - excite nuclei or produce new species

- explore their properties in a plasma, in a high (E,B) field, or via another excitation with secondary particles

possibility of different kind of particles on the same target !!To meet these requests we need several laser beams with different

energy and pulse length

Requests on laser characteristics

Collaborators:

CENBG, CNRS/IN2P3, Univ. Bordeaux 1

CEA/DPTA/SPT/Bruyères le Châtel

LULI, Polytechnique, Palaiseau

Members of the Institut Laser Plasma (France)

Open to other collaborators

• Phys. Rev. C 73, 045806 (2006) [7 pages] • Solar abundance of 176Lu and s-process nucleosynthesis• J. R. de Laeter* and N. Bukilic

• An accurate determination of the abundance of 176Lu is required because of the importance of this isotope in cosmochronometry, cosmothermometry, and s-process branching studies. An accurate abundance of 176Lu is also required as it is the parent nuclide of the 176Lu/176Hf geochronometer.