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

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

  • Slide 1
  • Nuclear Physics with ELI, Population/depopulation of Isomers: modification of nuclear level lifetime F. Gobet, C. Plaisir, F. Hannachi, M. Tarisien, M.M. Alonard CENBG, Universit de Bordeaux, CNRS,IN2P3 V. Mot, G. Gosselin, P. Morel, CEA/SPN, Bruyres le Chtel P. Audebert et al., LULI Polytechnique
  • Slide 2
  • 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(?)
  • Slide 3
  • 1) create a (warm and dense) plasma 2) create a bunch of high energy particles With a high power laser it is possible to : E 10 10 V/cm B 1000 T 3) Excite nuclei (inside the plasma) 4) Submit these nuclei to high electromagnetic fields or second production particles
  • Slide 4
  • Other deexcitation modes of the nucleus may appear: T 1/2 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: T 1/2 125m Te (first excited state at 35,49 keV) 52 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?
  • Slide 5
  • In a plasma excitation of intermediate states, can modify the effective lifetime of a nuclear state N.Klay et al. PRC 44,2839 (1991) 10 keV -- (n, )- 72 71 70 176 Lu abundance cosmochronometry, cosmothermometry, and s-process branching
  • Slide 6
  • 1) Petawatt laser to populate the isomer 2) laser (warm plasma) for isomer excitation 3) Observation of a 251 keV g 20 0.463 MeV = 3.4 keV 9 ns 0.248 MeVE =248 keV 32.7 d 85 Rb( ,n) 84m Rb M1 84 Rb Enhanced deexcitation of isomers : the 84 Rb isomer, a laboratory case similar to 176 Lu CENBG,LULI, CEA-DAM-DPTA, collaboration 85 Rb( g,n) 84m Rb: cross section just measured at the ELSA (19 MeV) electron facility (Bruyres le Chtel); analysis under process
  • Slide 7
  • 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, NEECprocesses) 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/cm 3 (Gosselin et al; PRC 70 (2004) 064603 and PRC 76 (2007) 044611 Excitation rate of the 6- level in 84 Rb as a function of the plasma charge state
  • Slide 8
  • Multilevel system: indirect deexcitation process or lifetime modification The 93 Mo m case: G.Gosselin, V.Meot and P.Morel PRC 76 (2007) 044611 Lifetime: ~5 orders of magnitude decrease 93 Nb(p,n) 93 Mo m 0.2 keV
  • Slide 9
  • 84 Rb Partial level scheme of 84 Rb Excitation energy 2 gammas to be detected 219.1 keV g 248 keV g
  • Slide 10
  • Long pulse large diameter (20 ns, =700 m) 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 converter 85 Rb Electrons Shielded ray detector Petawatt: electron production laser (50 fs, 10J, =20m ) 85 Rb(g,n) 84m Rb Absolute need : high repetition rate for the 2 laser beams Laser 1 Laser 2
  • Slide 11
  • High brightness for secondary particle sources: short pulse (10-100 fs) I > 10 20 W/cm 2 High repetition rate to overcome low cross sections : 1 Hz < rate < 1 kHz Large warm plasma long pulse (ns?): I~10 14 W/cm 2, focal spot ~500 m 2 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
  • Slide 12
  • Collaborators: CENBG, CNRS/IN2P3, Univ. Bordeaux 1 CEA/DPTA/SPT/Bruyres le Chtel LULI, Polytechnique, Palaiseau Members of the Institut Laser Plasma (France) Open to other collaborators
  • Slide 13
  • Phys. Rev. C 73, 045806 (2006) [7 pages] Solar abundance of 176Lu and s-process nucleosynthesis J. R. de Laeter* and N. BukilicJ. R. de LaeterN. 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.