Nuclear Physics with ELI Populationdepopulation of Isomers Cross Rate by MikeJenny

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									     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(?)
With a high power laser it is possible to :
               1) create a (warm and dense) plasma




                                             2) create a bunch of high
                                             energy particles
              protons,
             electrons,
              photons




                                              3) Excite nuclei (inside
                                              the plasma)
           E 1010 V/cm    4) Submit these nuclei to high electromagnetic
           B 1000 T       fields or second production particles
        Can nuclear lifetime be modified in a plasma?

What we know: the effect of the ionization on the electronic shells:
Internal Conversion can be modified, eventually suppressed: T1/2
                                                                           neutral
                   e-        125mTe
                                                                           t 1  1.49ns
                                      (first excited state at 35,49 keV)    2
                               52
(1)                                                                         48+
                                                                           t 1  11 ns
                                                                            2




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

Resonant Internal Conversion on unoccupied bound states has been shown.
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)
                   Can nuclear lifetime be modified in a plasma?
In a plasma excitation of intermediate states, can modify
the effective lifetime of a nuclear state
                   72

                   71




                          β-
              70          (n,)β-

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



                                                 176Lu  abundance
                                                 cosmochronometry, cosmothermometry,
                                                  and s-process branching
                Enhanced deexcitation of isomers :
          the 84Rb isomer, a laboratory case similar to 176Lu


                        2) laser (warm plasma) for isomer excitation
                                                                                9 ns

                                                              M1         D = 3.4 keV
         1) Petawatt laser          85Rb(,n)84mRb          0.463 MeV           20’
      to populate the isomer

                                     3) Observation          0.248 MeV           E=248 keV
                                      of a 251 keV 

                                                                                 32.7 d


   CENBG,LULI, CEA-DAM-DPTA, collaboration                               84Rb

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)

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



                                                     Hypothesis:
                                                     T° plasma ~ 2keV:
                                                     charge states >28 during Dt: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
    Multilevel system: indirect deexcitation process or
                   lifetime modification

 • The 93Mom case:




                                     0.2 keV
93Nb(p,n)93Mom

                             Lifetime: ~5 orders of magnitude decrease
     G.Gosselin, V.Meot and P.Morel PRC 76 (2007) 044611
                                      84Rb


  Excitation energy




                                                                 219.1 keV 
                      248 keV 

                                  Partial level scheme of 84Rb


2 gammas to be detected
                                                       85Rb(,n)84mRb
          Petawatt:
  electron production laser
    (50 fs, 10J, =20µm)
                      converter
                                         85   Rb
                                        


     Laser 1            Electrons
                                                       Shielded  ray
                                                        detector
                Al target
                                    Laser 2




Absolute need :
high repetition rate
for the 2 laser beams           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
             Requests on laser characteristics
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
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.

								
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