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b -n decay spectroscopy

T NNERRE. b -n decay spectroscopy. TAS Workshop Caen, March 30-31, 2004. The b -decay-n decay Spectroscopy TONNERRE : specifications Results of Physics Experiments Conclusions and Perspectives. J.C. Angélique for TONNERRE Collaboration.

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b -n decay spectroscopy

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  1. T NNERRE b-n decay spectroscopy TAS Workshop Caen, March 30-31, 2004 • The b-decay-n decay Spectroscopy • TONNERRE : specifications • Results of Physics Experiments • Conclusions and Perspectives J.C. Angélique for TONNERRE Collaboration

  2. When N>>Z : Qb , Sn b-delayed neutrons emissiondominant decay mode Exple: 11Li : Qb=20.6 MeV Sn=0.7 MeV Pn~92% b-n decay A-1Z+1N-3 Enaccess to the location and structure of unbound levels Eneutrons Eg A-1Z+1N-2 T NNERRE essential information to map the b-strength function comparisons with theorical predictions (Shell Model…) complete b-g-neutron spectroscopy The b-delayed neutrons decay b-decay: fundamental tool for the investigation of nuclei far from stability. • decay mechanism (Fermi or Gamow-Teller transitions) is well understood  J,p • complementary to other processes: transfer reactions... • applicable at low intensities AZN S2n b-decay Qb Sn Eg AZ+1N-1

  3. TONNERRE TONneaupour NEutRonsREtardés A new detector for Delayed-Neutron Spectroscopy (Collaboration LPC Caen - IFIN Bucarest) SCINTILLATORS Buta A. et al., NIM A455 (2000) pp. 412-423 T NNERRE • Up to 32 scintillators plastic bars • En by TOF , 200 keV < En < 5 MeV • solid angle : up to 45% of 4p • DE(1 MeV): ~ 80 keV • e(1 MeV) ~50 % First test in April 98 (GANIL)

  4. T NNERRE A. Buta et al, NIM A 455 (2000) 412-423 TONNERRE STATUS

  5. know better the region near "island of inversion" around N = 20 N=20 35Al 32Al 33Al 34Al 31Al Si Al 26 Mg 32Mg -926 33Mg -1090 34Mg -685 2 hw excitations Na Ne 24 22 F island of inversion 8 O 20 31Na -502 32Na -1295 33Na -427 18 N C B 16 12 14 Be 30Ne -698 31Ne -891 32Ne -128 Li 10 He 8 E.K. Warburton et al., PRC41(1990) A. Poves et al., NPA 571 (1994) Y. Utsumo et al., Phys. Rev. C60 (1999) 4 6 H 2 E333: b-n-decay of 32,33Mg and 34,35Al Complete neutrons and gammas spectroscopy T NNERRE

  6. Low energy neutron det Leps beam Implant. plastic Exit window Si detector Clover • HI and b : Plastic (N=20) • gammas : 2 Ge clovers (EXOGAM) + 1 LEPs • neutrons : Plastics scintillators T NNERRE E333 Set Up GANIL April 2000 • production of neutron-rich nuclei below 36S • by projectile fragmentation ( 78 MeV/A) • Be (target) • selection using the LISE3 spectrometer • 32, 33Mg, 34, 35Al

  7. 34Al g spectrum ISOLDE: 1999 Beam Time ~ 12 h 34Al g spectrum ( zoom) Intensity ~ 30 pps 12 little neutrons detectors 34Al b-g-n coïncidence TOF(a.u.) GANIL: 2000 Beam Time ~ 8 h 34Al b-g-one neutron coïncidence Intensity ~ 300 pps 19 modules of TONNERRE T NNERRE TOF(ns) 34Al b-nDecay

  8. To mix or not to mix ? 34Al S. Nummela et al. Phys. RevC 63 (2001) T 1/2= 56 (5) ms b-n S. Piétri thesis LPC-Caen T02-03 (2003) En (MeV) 3.57 2.64 2.091.731.23 0.86 B. Fornal et al.,PRC 49 2413 (1994) W. Mittig et al. EPJA (2002) N. Iwasa et al. Phys. RevC 67 (2003) n Pn =26(4)% 1435 1010 0 7/2- 7/2+ 1/2+ 3/2+ 1/2+ 3/2+ Sn = 7530 keV sd-shell 33Si b 2+ 4+ 4970 4379 4255 3326 2133?? (3,4,5)- (3,4)- 3- 2+ 4519 1193 1193 keV ??? 2+ 02+ ??? 02+ e+ e- C.E. T NNERRE 01+ 0 MCSM 34Si sd-shell Y. Utsuno et al.,PRC 64 011301R (2001)

  9. Our results on the 32Mg b-decay : - t1/2:85 ± 5 msec (120 ± 20 msec) M. Langevin et al., NPA414(1984)151 - Pn :3.4± 0.2 % (2.4± 0.5 %) - neutrons : 350 300 250 20015010050 5 1  4.51 MeV 2  2.79 MeV 3  1.78 MeV 4  1.28 MeV 5  973 keV 6  680 keV 7  370 keV number of counts 6 3 4 2 7 1 T NNERRE 40 60 80 100 120 140 160 180 200 time of flight (ns) - g' rays :222 - 735 - 2465 - 2735 keV (old) D. Guillemaud-Mueller et al., NPA426(1984)37 564.5 – 787.5 – 1743.5 - 2030 -3202 keV (new) number of counts 300 400 500 600 700 800 900 1000 1500 2000 2500 3000 energy (keV)

  10. What are the limits of the "island of inversion” ? After Before E333 experiment low energy structure 32Al not pure usd • New g-lines in the 33Al structure • Alimentation of 4+ and 4- levels in 32Al by b-n decay of 33Mg 33Al unknown 32Mg 32Mg b-n b-n T 1/2= 120 (20) ms T 1/2= 120 (20) ms 33Mg 33Mg (3/2)+ (3/2)+ Pn=2.5 % Pn=2.5 % T 1/2= 86 (5) ms b b 2 + not usd T 1/2= 90 (20) ms T 1/2= 90 (20) ms Pn=17.5 % Pn=17.5 % 1+ 1 + usd T 1/2= 93 (11) ms En (MeV) 2.48 1.92 0.630.460.41 0.28 1+ 3 + b-n b-n n 2 + 3 + (4-) (4-) (4+) (4+) isomer 200ns isomer 200ns b b 2+ 2+ 2+ 4+ 1+ 1+ 1+ usd 32Al Eg (keV) 4735 2894 2761 2364 2096 1838 1646 1617 1467 1046 594 80%occurs to normal USD configurations 20%occurs to more complicate structure B. Fornal et al., PRC55 762(1997) B. Fornal et al., PRC55 762(1997) T NNERRE I.O.I. has no sharp boundaries M. Robinson et al., PRC53 R1465(1996) M. Robinson et al., PRC53 R1465(1996) 33Al C. Timis thesis LPCCaen T01-01 (2001) M. Langevin et al., NPA 414 151 (1984) M. Langevin et al., NPA 414 151 (1984) S. Grévy et al., NPA to be published

  11. Theoretically Modification of the shell structure at N=28 • Shell model (Retamosa et al.) • erosion of the shell gap N=28 p3/2 28 36S20 16 f7/2 20 Z=20 d3/2 d3/2 16 s1/2 Z=16 s1/2 d5/2 d5/2 p n J. Retamosa et al. PRC55(1997)1266 Z=14 p3/2 28 44S28 16 f7/2 20 • Rel. Hart. + Bogol. (Lallazissis et al.) d3/2 d3/2 shell gap N=28 is well broken s1/2 s1/2 14 d5/2 d5/2 T NNERRE • Experimentally - t1/2 and Pn around 44S Sorlin et al. (GANIL) - COULEX of S and Si isotopes Glasmacher et al. (MSU) - Mass measurement below 48Ca Sarazin et al. (GANIL) • In-beam g-spectroscopy in S (GANIL) D. Sohler et al. PRC66(2002)054302 p3/2 28 44S28 16 f7/2 20 d3/2 d3/2 s1/2 s1/2 14 • Hart.Fock + Bogol.(Péru et al.) d5/2 d5/2 p n p3/2 28 42Si28 14 f7/2 20 d3/2 d3/2 s1/2 s1/2 14 d5/2 d5/2

  12. beam • HI and b :DS-Strip Si + 2 plastics • gammas : 3 Ge clovers (EXOGAM) + 1 LEPs • neutrons : Plastics scintillators T NNERRE E377 Set Up GANIL June 2001 • production of neutron-rich nuclei below 48Ca • by projectile fragmentation ( 77 MeV/A) • Be (target) • selection using the LISE3 spectrometer • 40, 41, 42Si, 42,43,44P , 44,45,46.S, 46,47.Cl

  13. EVIDENCE OF STRONG DEFORMATION ? • Are the Si isotopes deformed ? 39Si QRPA t1/2(39Si) = 47.52.0 msec 42Si t1/2 (Qb-E*)-5 time (msec) sphérical exp. exp. exp. exp. t1/2(40Si) = 33  1 msec 40Si time (msec) K. L. Kratz and B. Pfeifer 41Si t1/2(41Si) = 20.02.5 msec deformed time (msec) 42Si t1/2(42Si) = 12.53.5 msec time (msec) T NNERRE -0.3 -0.2 0 0.2 0.3 déformation (e2) • half-lives of Si isotopes

  14. 46Ar28 48Ca28 N=28 - complete spectroscopy of 44,45,46Ar 18 20 f7/2 f7/2 d3/2 d3/2 d3/2 p3/2 s1/2 s1/2 s1/2 s1/2 28 d5/2 d5/2 d5/2 d5/2 20 20 14 5/2- 2420 7/2- 2260 2140 1/2- p n 1/2- 1790 J. Mrazek, S. Grévy et al, 5/2- 1330 p3/2 1240 3/2- 28 3/2- 420 20 20 7/2- d3/2 SM (Nowacki) 14 Very good agreement Expt. vs. SM up to 2 MeV. p n • (3/2-)1 state at 543 keV (only 15% intruder) •  progressive reduction of the N=28 shell gap when protons are removed • (3/2-)2 state at 1340 keV •  main part of the intruder strength T NNERRE 16 n

  15. Problematic of the potassium isotopes • Inversion of the ps1/2-pd3/2 orbitals • b decay of K→Ca: connection between the two problematics Characteristics of b decay for neutron rich nuclei : • large Qb window (~15 MeV in K) and low Sn (~4 MeV) • high emission probability of 1 or 2 delayed neutron (Pn~40-90%)  Different prediction on Jp ground state for N>28 depending on the interaction We need a very efficient neutron and gamma detection to perform b-g and b-n-g coincidences IReS Frédéric PERROT Interest of heavy calcium isotopes 2+ levels systematic in even-even Ca isotopes Evidence of the semi-magic character of 52Ca: • Shell closure at Z=20 • Subshell closure at N=32: high Ex of the 2+ state at 2.56MeV with a (np3/2)3-(np1/2)1 configuration How to get information on the position of the f5/2 orbital ? • Ex of the 4+ state in 52Ca: (np3/2)1-(nf5/2)1 • Ex of the 2+ state in 54Ca: (np1/2)1- (nf5/2)1  discrimination between two interactions

  16. ISOLDE Experiments : September 2002 and July 2003 (Z=20) IReS

  17. TOF spectrum from 52K decay IReS Fréderic Perrot

  18. 53K decay: preliminary results in progress IReS

  19. T NNERRE Conclusion Use with Gamma detectors ( EXOGAM, MINIBALL...)  High performance instrument for decay spectroscopy of neutron-rich nuclei Actual physics programms  Spectroscopy in the region of N  20: 32, 33Mg, 34, 35Al  Spectroscopy in the region of N=28 : 40, 41, 42Si, 42,43,44P , 44,45,46.S, 46,47.Cl  Spectroscopy in the region of Z  20: 51,52,53K Mobility of TONNERRE  ISOLDE, GANIL (LISE) ... …. Why not on SPIRAL low energy ? Need some minimum conditions………….

  20. T NNERRE …..Conditions: 1) What beam will be available ??????  region of A  20: 19,...C , 21,...N, …  region of N  20: 30,...Ne , 33,...Na, 34,…Mg, …  region of N=28 : 44,…Si , 45…P, 48…Cl,...  region of Z  20: 54,... K, 54,...Ca, …  8He ? 2) What intensity > LISE, SISSI , ISOLDE..???? > 1 pps, b (T 1/2) > 10 pps, b-g or b-n > 100 pps, b-g -g or b-g -n , ... 3) What identification ????? Event by event , T 1/2, b, g 4) What experimental area??? Background,area>20 m2

  21. T NNERRE COLLABORATION T NNERRE LPC - Caen – France N.L. Achouri, J. C. Angélique, G.Ban, S. Grévy, F. R. Lecolley, E. Liénard, N. A. Orr, J. Peter and S. Pietri IFIN – Bucharest – Romania C. Borcea, A. Buta, F. Negoita, D. Pantelica and M. Stanoiu IreS – Strasbourg - France P. Baumann, G. Canchel S. Courtin, P. Dessagne, C. Jollet, F. Maréchal, F. Nowacki and F. Perrot FLNR – Dubna - Russia Y. Penionzhkevich, S. Lukianov and O. Tarasov GANIL - Caen – France F. de Oliveira, M. Lewitowicz, I. Stefan and C. Stodel IPN – Orsay – France F. Ibrahim, D. Guillemaud Mueller, F. Pougheon, O. Sorlin DAM – Bruyères le châtel J. M. Daugas, V. Meot and O. Roig Univ. of Surrey - UK W. Catford and C. Timis Nucl. Phys. Inst. – Czech Republic Z. Dlouhy and J. Mrazek

  22. Nuclei A at/s ISOLDE at/s ALTO K 49 50 51 52 53 5.4.105 7.4.104 9.103 1.2.103 4 Na 33 34 40 2 Nuclei A at/s ISOLDE at/s SPIRAL 2.102 3-6.103 1.5.104 4.105 Al 34 35 2.6 8 Kr 71 72 73 74 75 3.5 3.103 5.105 2.106 1.8.107 Ni 69 70 4.104 2.104 2.104 1.104 Cu 76 77 78 79 4.104 4.103 4.102 1 2.104 2.103 2.102 Sr 75 76 77 78 5 4.103 2.105 9.2.105 Zn 76 78 80 3.2.107 2.106 2.104 5.9.105 2.105 2.104 Rb 74 2.103 Ga 62 400 Sn 128-132 133 134 135 136 137 4 - 6.108 3.107 4.106 2.105 6.103 2.102 1.2.106 Yield information ISOLDE :http://isolde.web.cern.ch/isolde/ Ulli Koster SPIRAL: http://www.ganil.fr/operation/available_beams/ radioactive_beams.htm ALTO: Fadi Ibrahim (preliminary estimation)

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