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as an alternative testament to super heavy elements stability

. LLC with  ≥10 -18 s. as an alternative testament to super heavy elements stability. Fission time measurements. ♪   Z=120 and 124 ♫    not 114 . Information on SHE islands of stability from fission time measurements.

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as an alternative testament to super heavy elements stability

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  1. LLC with ≥10-18s as an alternative testament to super heavy elements stability Fission time measurements ♪ Z=120 and 124 ♫   not114

  2. Information on SHE islands of stability from fission time measurements • Measurements done using blocking effect in single crystals for 3 systems: COLLABORATION/: GANIL Caen, IPN Orsay, SPhN Saclay, GPS Paris, IPN Lyon 208Pb + Ge  Z=114 (A=282) 238U + Ni  Z=120(A=296) 238U + Ge  Z=124(A=312) 3 predicted magic Z numbers (depending on the models) High excitation energies E* < 80 MeV σER with Z  extract information relative to stability from the dominant deexcitation channel i.e. fission • Measurements proposed using the Atomic clock method: COLLABORATION/: GANIL Caen, IPN Orsay, CEA/IRFU/SPhN Saclay, LPC Caen,CEA/DIF/DPTA/SPN Bruyères le Chatel, Université Laval, Québec INFN Legnaro, INFN /Univ. Padova, INFN /Univ. Milano, INFN /Univ. Firenze 238U + Ni  Z=120(A=296) ~ D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  3. Fission times of highly excited super-heavy nuclei ~ 10-22 s ~ 10-21 s init 10-21 s  Probability fission n Quasi-fission time range measured by J. Töke et al., Nucl. Phys. A 440 (1985) 327, from the angular distributions fission n  10-20 s fission n fission fission n n E* Lifetime fission fission p n fission fission fission n  10-18 s n fission fission fission n n n fission fission fission =0 ~ 10-12 s The lifetimes of the residual nuclei after particle emission strongly increase when E* decrease Competition between fission and particle emission at each step of the cooling: very broad fission time distributions Tail at very long times (t > 10-18 s) in highly excited SHE fissions? • fission barriers • friction • shell effects restoration • pairing effects • saddle configuration • level densities at saddle……. Advantages: • discrimination between fusion followed by fission and quasi-fission • The tail at long times and the nuclear stability are strongly correlated • direct evidence for a tail at long times can be reached using the blocking technique in single crystals and/or using inner shell ionization decay processes as an atomic clock

  4. F. Goldenbaum et al., PRL 82 (1999) 5012 Blocking technique in single crystals D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  5. Blocking technique in single crystals Lower sensitivity limit (tmin) given by geometrical effects (thermal vibration amplitude) 1.0 Normalized yield 0.5 For the 3 systems,tmin≈ 10-18 s For a perfect crystal, treactminmin min ( tmin) 0. 0.5 1.0 (deg)  = 0 Direction of the crystal axis For a given selection of events, min= Yield in the axis direction (at  =0) ; depends only, for a given crystal, on reaction time (first order approximation) min> min (tmin) treac> tmin D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  6. Experimental set-up Blocking telescopes 0.02°angular resolution (Z , E , reaction time) INDRA 4p detector (Z, E , q , f , Alcp) Control on the reaction mechanisms: light charged particles, IMFs, heavy fragments detected on 4p rejection of possible incomplete fusion reactions, pre-equilibrium…. D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  7. 208Pb + Ge 6.16 MeV/u 238U + Ni 6.62 MeV/u Blocking dips to search for a fusion-fission Component among the quasi-fission events? Scattered projectile-like 238U + Ge 6.09 MeV/u Atomic Number Projectile-like sequential fission Projectile-like sequential fission Energy ( MeV) Energy ( MeV) Energy ( MeV) Quasi elastic target Quasi- fission +? Fusion-fission D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  8. Direct evidence for long times: Z=120 cmin  0.2  treac > 10-18 s 1.2 1 0.8 0.6 Fusion-Fission? 0.4 0.2 0 1.2 U sequential fission + …….. 1 0.8 Normalized Yield 0.6 0.4 0.2 0 Quasi-elastic (target) 1.2 1 0.8 0.6 0.4 0.2 0 0 0.2 0.4 0.6 0.8 Y (deg) treac < tmin(thermal vibrations)  cmin  0.1 tmin 10-18 s D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  9. Characteristics of fragments detected at 20 deg with 60 ≤ Z1 ≤ 85 (U + Ni) Counts Total charge Ztot χmin (%) Kinematics in good agreement with expectation for fission fragments Ni IE QF-FF QNi FSU Normalized counts  Kinetic energy in agreement with Viola systematics Ektot (MeV) TKE (MeV)  Reaction time longer than 10-18s for at least 10% of the events  Binary with Z1 + Z2 = 120 • Very low intermediate mass fragment multiplicity (MIMF ≈ 4 10-3,as detected by INDRA) as well as light charged particle multiplicity ≈ 7 10-2 , as detected by INDRA Fusion-fission component high fission barriers D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  10. Direct evidence for long times: Z=124 Scattering events t < tmin→ χmin~ 0.1  χmin~ 0.2 → t > tmin Scattering events t < tmin→ χmin~ 0.1 D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  11. Search for long lifetime tail in 208Pb + Ge --> Z = 114 No selection Binary fission  Scattering events t < tmin→ χmin~ 0.2 χmin~ 0.2 χmin~ 0.2 min evolution: - long lifetimes for sequential fission of projectile-like fragments - no hint for long lifetimes for Z = 114 , A = 282 D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  12. From P. MÖLLER et al. At. Dat. And Nucl. Dat. Tab. 59 (1995) 185 Z Bf (MeV) Möller et al. Bf (MeV) Berger et al. * 124 , 312 0.2 8.8 120 , 296 6.8 11.1 114 , 282 6.7 6.3 * HFB calculations by J.F. Berger et al., Nucl.Phys.A685 (2001) 1 LLC LLC Bf >> 0 E*(t=0) ≤80MeV Bf (T)? M. Morjean et al PRL 101 (2008) 072701 M. Morjean et al PRL 101 (2008) 072701 The fission barriers involved for the long fission times are the fission barriers for all the isotopes formed in the cooling chain D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  13. 296120 Bf (MeV) 238U T (MeV) Bf(T)/Bf(T=0) (%) T (MeV) Evolution of the fission barriers with T WORK IN PROGRESS, J.F. Berger, CEA/DAM,Bruyères le Chatel M. Laget Thesis, Oct 2007 Univ Paris XI, Orsay • Stronger pairing at saddle point as compared to ground state • progressive disappearence of pairing with T occurs for lower temperature at gs than at saddle point D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  14. Conclusions from blocking fission time measurements Evidence for survival with large probabilities of excited nuclei with Z= 120 and Z = 124 at times longer than 10-18s, only compatible with compound nucleus formation Tails at fission times longer than 10-18s for Z = 120 and Z = 124 imply very high fission barriers for these elements. HFB calculation at finite temperature predict significant Bf increase at moderate temperature Magic spherical numbers in the vicinity? Shell effects for deformed nuclei? The blocking technique has been demonstrated to be a powerful probe to test SHE stability, but the requirements regarding the target induce limitations on the studied systems that prevent from a careful analysis of the precise location and extension of the stability island(s) D. JACQUET: IPNO, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France

  15. 1500 1500 2000 2000 500 500 1000 1000 t (10-21s) t (10-21s) Stabilisation importante des noyaux à l’approche de la fermeture de couche en neutrons à N=184 Implementation of an alternative fission time measurement technique based on inner shell vacanies decay 6.6 MeV/u 238U+58,64Ni ☺64,58Ni allow to explore neutron shell closure influence on fission time ☺Availability of a new probe to scan SHE stability and locate next Z & N magic numbers 298114 ☺Independent confirmation of the long fission times observed for Z=120 N=184 Bf (MeV) 124 120 304114 Bf (MeV) Bf (MeV) N=190 114 t (10-21s) Y. Aritomo, Phys.Rev. C75 (2007) 024602 HFB calculations, M. Laget Thesis, Orsay 2007

  16. Inner Shell Ionization during the collision Adjustment of electronic orbital United Atom orbitals With an ionization probability PK,LZp2 Which can be measured through coincidences between X & elastic scattering events If the fission time f of the heavy system is similar to the inner shell vacancies lifetime xthe UA vacancies will disappear through the competition between fission and X-ray emission , and if one assumes a single exponential decay dNK/dt=NCN(t)e-twith =1/X and NCN=N0e-t/f =x +f K-1  L-1  X rays f = x Nx PKNf-Nx fission M,N-1  The Atomic Clock Method

  17. COLLABORATION IPN Orsay: D. Jacquet , F. Azaiez, M.F. Rivet , L. Tassan Got INFN Legnaro: M. Cinausero, F. Gramegna, V. Kravtchouk, V. Rizzi INFN/Université Milano: A. Bracco, A. Corsi, F.C.L. Crespi, O. Wieland, INFN/Université Padova: D. Fabris, G. Montagnoli INFN/Université Firenze: S. Barlini GANIL: N. Alahari, A. Chbihi , G. De France , J. Frankland , M. Rejmund , M Morjean, C. Schmitt CEA/IRFU/SPhN: A. Drouart , L. Nalpas, C. Simenel CEA/DIF/DPTA/SPN Bruyères le Chatel: X. Ledoux LPC Caen:N. Le Neindre, M. Parlog Université Laval, Québec: R. Roy, M.O. Frégeau

  18. 3 HpGe X detectors Z1,E1,M1 target 1=17.5±7.5 ° VAMOS Telescope for elastic scattering Fission fragments telescopes E2,Z2,2 • Asymmetric fission of Z=120, light fragment in Vamos, Heavy one in the FF telescopes • Double coincidence FF1-FF2 light fragment A and Z distribution • Double coincidence X-FF2  full statistics for time measurements for 1 Vamos tuning double coincidence X-FF  • search for time effects for doubly magic FF • Triple coincidence for sequential U selection , Ztot validation for SHE 120, study of QF/FF • ratio f()

  19. Kβ3 : 110.42 keV Kβ1 : 111.30 keV Kβ’’5 : 111.96 keV Kβ2 : 114.41 keV Kβ4 : 115.01 keV KO2,3 : 115.38 keV Kβ3 : 110.42 keV Kβ1 : 111.30 keV Kβ’’5 : 111.96 keV 12.3% 36% 36% Counts K2 : 94.67 keV 62.5% K1 : 98.44 keV 100% } } E 238U (6+4+) 158.8 keV E 238U (8+6+) 211 keV (100 eV)

  20. Saddle point Ground state T = 0 MeV Potential T = 0 MeV T T = 0.3 MeV Pairing energy T = 0.4 MeV T = 0.5 MeV V T = 0.6 MeV β2 Bf (MeV) 296120 β2 T (MeV)

  21. d2σ/(dA. dTKE) 6A.MeV 238U + 64Ni Projectile Target 58Fe+244Pu 300 200 100 CompositeSystem Fusion Total Kinetic Energy TKE Quasi-fission Fusion Quasi-fission NC Fission Mass Asymmetry RelativeDistance 40 80 120 160 200 240 Y. Aritomo, M. Otha, Phys. Of Atomic Nuclei 66 (2003) 1105 Fragment mass A … From J. Töke et al, NPA440 (1985) 327 Evaporation Residue Fast fission :dominant process for such heavy systems

  22. 238U + Ni 6.62 MeV/u θ=20° At least 10% to 15% of events with t > 10-18s 1.0 - Normalized yield Exp. <Z/E>=0.1179, 33% Zion-Qion=33.9→aTF=0.1056Å Heavy Fragments Monte Carlo calculations No recoil  << 10-19 s Exp ≡conv 2.5 mrad Heavy fragments zone populated by quasi fission and fusion fission events 1.0 - Exp. <Z/E>=0.034 Zion-Qion=4→aTF=0.1137Å Normalized yield Quasi target Quasi-fission Fast process t < 10-20s Probability 0 0.1 0.2 0.3 0.4 0.5 Ψ(deg) C.N. Fission Pllc Time (s) • Complex time distribution Lowest estimate of f given by F(t)=1/ e –t/  =2.25 10-18s

  23. Mass asymmetry deformation Relative distance

  24. Search for long lifetime tail in 208Pb + Ge --> Z = 114 Coincident fragment in INDRA No selection Sequential fission Binary fission Heavy fragment partner of the light QF fragment  detected at 20°

  25. Y. Aritomo, Phys.Rev. C75 (2007) 024602 298114 304 114

  26. Déformations axiale uniquement γ 296120 Barrière triaxiale Barrière axiale xOy xOy yOz yOz xOz xOz Stabilisation importante des noyaux à l’approche de la fermeture de couche en neutrons à N=184 Hauteurs de barrières à température nulle Restrictions du calcul Noyaux pair-pair uniquement

  27. Z=120 A=296 E*=67 MeV Tlim=1MeV 10-17 40% increase of Bf 102 increase on tf tfission (s) 10-18 10-19 10-20 kmul (multiplicative factor applied on fission barriers) Correlation between Fission barrier and fission time Crude estimate : Fission times calculated through standard Bohr and Wheeler statistical model, with fission barriers from Moller arbitrarily multiplied by a reduction factor kmul for all the nuclei along the deexcitation chain before fission

  28. Motivations • Variation de Bf(T) mal connue •  Paramétrisations empiriques • Contributions macroscopique, effets de couches et appariement traités séparément • Superlourds : importance majeure des effets microscopiques sur Bf • utilité d’une description la plus précise possible à ce niveau  Théorie HFB à température finie : • Prise en compte de l’appariement de manière totalement auto-cohérente par l’utilisation de l’interaction D1s de Gogny, permettant la description à la fois des champs moyen et d’appariement. • Température prise en compte par la minimisation du potentiel grand-canonique • Noyaux étudiés :

  29. 1 0 1 1 0.2 0.4 0.6 0 200400 600800 1000 Y (deg) Energy (MeV) M. Morjean et al PRL 101 (2008) 072701 Pb+Ge 6.16 MeV/u From P. MÖLLER et al. At. Dat. And Nucl. Dat. Tab. 59 (1995) 185 Atomic Number  LLC with ≥10-18s Normalized Yield 40 No selection 20 Binary fission No clear evidence of LLC for this n deficient nucleus 0.6 0.4 0 200400 600800 1000 0.2 Y (deg) Energy (MeV) U+Ge 6.09 MeV/u U+Ni 6.62 MeV/u 1.2 100 100 0.8 0.6 0.4 0.2 Atomic Number Atomic Number 1.2 Normalized Yield Normalized Yield 0.8 0.6 0.4 0.2 40 40 1.2 0.8 0.8 20 20 0.6 0.6 0.4 0.2 0.4 0.6 0.8 0.2 0 200400 600800 1000 Energy (MeV) Y (deg)

  30. Le blocking cristallin: Un chronomètre original pour traquer des noyaux super-lourdsCollaboration entre l’IPN d’ Orsay et le GANIL, l’IPN de Lyon, le SPhN Saclay et l’INS de Paris. Vibns thques + Défauts min=f(Thermal vibrations / velocity of nucleus )< fiss< max

  31. Z=120 1.10-18<  <5. 10-18 s K(Z=120) =(2.8  0.2)  1018 s Marek Polasik, Institute of Physics, Nicholas Copernicus University, 87-100 Toruń, ul. Grudziadzka 5, Poland

  32. Characteristic X-Ray shape For  ≥ 20 where =Ex/ħ Z=120Ex=180 kev.  ≥ 20   ≥ 7. 10-20 s From R. Anholt Rev. Mod. Phys. 57 (1985) 995

  33. 1.0 Normalized yield 0.5 0. 0.5 1.0 (deg)  = 0 Direction of the crystal axis min= Yield in the axis direction (at  =0) ; depends only, for a given crystal, on reaction time (first order approximation) Blocking technique in single crystals Lower sensitivity limit (tmin) given by geometrical effects (thermal vibration amplitude) For E416 and E416a expts tmin≈ 1 as =10-18s Quadratic evolution of min with t above tmin and min(t=)=1 min = 1 - A 1+B t2

  34. Blocking experiments Quadratic dependence of For Ni at room T min(t0)= min(t=0)+0.0177t2 min(t=0)=0.17 , min(t=)=1 min = 1 - 0.83 1+0.0177t2 mes=(1-R) min(t<tlim)+R min(t>tlim) mes- min(t=0) [1+ 1 ] 1- min(t=0) 0.0177t2 R= Fraction R • = 10-17 R=0.3 Fission time (as) Evolution of the fusion fraction R For a measured min = 0.33 min

  35. NXcl+at PK ( Nfis+NQF ) cl RX=  Concernig the FF/QF mixing Rblock at=5 as at=1 as

  36. For E416 experiment, Ni crystal measured min for elastic events (t<<tmin) ~0.17 And min(t>tmin)= min(t<<tmin)+0.0177t2 min = 1 - 0.83 1+0.0177t2 Considering the two processes fusion-fission and quasi-fission, if R is the fraction of fusion-fission, the experimentally measured min value will be mes=(1-R) min(t<<tmin)+R min(t>tmin) i.e. different times t>tmin can lead to the same measured mes Provided the fraction R of fusion events vary R= mes- min(t<<tmin) [1+ 1 ] 1- min(t<<tmin) 0.0177t2 Evolution of the fraction R of fusion events in a QF/FF mixing for which mes = 0.33 For instance • = 10-17 R=0.3 Fraction R Fission time (as)

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