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

 - decay : fundamental tool for the investigation of nuclei far from stability. decay mechanism (Fermi or Gamow-Teller transitions) is well understood  J,  complementary to other processes: transfer reactions... applicable at low intensities The  -delayed neutrons decay T NNERRE AZNAZN A Z+1 N-1 QQ EE  -decay SnSn S 2n essential information to map the  -strength function comparisons with theorical predictions (Shell Model…) complete  -  -neutron spectroscopy E n  access to the location and structure of unbound levels Exple: 11 Li : Q  =20.6 MeV S n =0.7 MeV P n ~92% When N>>Z : Q , S n  - delayed neutrons emission dominant decay mode EE A-1 Z+1 N-2  -n decay A-1 Z+1 N-3 E neutrons

TONNERRE TON neau pour NE ut R ons RE tardés A new detector for Delayed-Neutron Spectroscopy (Collaboration LPC Caen - IFIN Bucarest) First test in April 98 (GANIL) Up to 32 scintillators plastic bars E n by TOF, 200 keV < E n < 5 MeV solid angle : up to 45% of 4   E(1 MeV): ~ 80 keV  (1 MeV) ~ 50 % T NNERRE Buta A. et al., NIM A 455 (2000) pp SCINTILLATORS

T NNERRE A. Buta et al, NIM A 455 (2000) TONNERRE STATUS

know better the region near "island of inversion" around N = Li Be B C N O F Ne Na Mg Al Si N=20 H He E333:  -n-decay of 32,33 Mg and 34,35 Al Complete neutrons and gammas spectroscopy E.K. Warburton et al., PRC41(1990) A. Poves et al., NPA 571 (1994) Y. Utsumo et al., Phys. Rev. C60 (1999) island of inversion 33 Al 34 Al 35 Al 2 hw excitations 32 Al 33 Mg Mg Na Na Na Ne Ne Ne Mg Al T NNERRE

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

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

33 Si  -n-n MCSM Si 34 Al S n = 7530 keV sd-shell 2+ To mix or not to mix ? 7/2+ 1/2+ 3/2+ sd-shell S. Piétri thesis LPC-Caen T02-03 (2003) S. Nummela et al. Phys. RevC 63 (2001) ?? (3,4,5)- (3,4) e+ e- C.E ??? T 1/2 = 56 (5) ms Pn =26(4)% 1193 keV ??? 4519 W. Mittig et al. EPJA (2002) N. Iwasa et al. Phys. RevC 67 (2003) /2- 1/2+ 3/2+ B. Fornal et al.,PRC (1994) n E n (MeV) Y. Utsuno et al.,PRC R (2001)

 Our results on the 32 Mg  -decay : - t 1/2 :85 ± 5 msec(120 ± 20 msec) M. Langevin et al., NPA414(1984)151 - Pn :3.4 ± 0.2 %(2.4 ± 0.5 %) -  ' rays : keV (old) D. Guillemaud-Mueller et al., NPA426(1984) – – keV (new) number of counts energy (keV) - neutrons : number of counts time of flight (ns)  4.51 MeV 2  2.79 MeV 3  1.78 MeV 4  1.28 MeV 5  973 keV 6  680 keV 7  370 keV T NNERRE

33 Al unknown low energy structure 32 Al not pure usd Before E333 experiment What are the limits of the "island of inversion” ? 1+1+ M. Langevin et al., NPA (1984) 33 Mg isomer 200ns (3/2) + 32 Mg  -n  T 1/2 = 90 (20) ms (4 + )  -n 2+2+ P n =2.5 % P n =17.5 %  (4 - ) T 1/2 = 120 (20) ms B. Fornal et al., PRC (1997) M. Robinson et al., PRC53 R1465 (1996) usd Al 1+1+ M. Langevin et al., NPA (1984) 33 Mg isomer 200ns (3/2) + 32 Mg  -n  T 1/2 = 90 (20) ms (4 + )  -n 2+2+ P n =2.5 % P n =17.5 %  (4 - ) T 1/2 = 120 (20) ms B. Fornal et al., PRC (1997) M. Robinson et al., PRC53 R1465 (1996) 32 Al E  (keV) n C. Timis thesis LPCCaen T01-01 (2001) New  -lines in the 33 Al structure Alimentation of 4 + and 4 - levels in 32 Al by  -n decay of 33 Mg After E n (MeV) T 1/2 = 93 (11) ms I.O.I. has no sharp boundaries 80% occurs to normal USD configurations 20% occurs to more complicate structure S. Grévy et al., NPA to be published usd T 1/2 = 86 (5) ms not usd T NNERRE

- t 1/2 and P n around 44 S Sorlin et al. (GANIL) - Mass measurement below 48 Ca Sarazin et al. (GANIL) - COULEX of S and Si isotopes Glasmacher et al. (MSU) Experimentally - In-beam  -spectroscopy in S (GANIL) D. Sohler et al. PRC66(2002) Z=20 Z=16 Z=14 J. Retamosa et al. PRC55(1997)1266 Theoretically - Rel. Hart. + Bogol. (Lallazissis et al.) - Shell model (Retamosa et al.) erosion of the shell gap N=28 shell gap N=28 is well broken f7/2 p3/2 d3/2 s1/2 d5/2  36 S f7/2 p3/2 d3/2 s1/2 d5/2 44 S d5/ d3/2 s1/2 14 d3/2 s1/2 d5/ Hart. Fock + Bogol. (Péru et al.) f7/2 p3/2 d3/2 s1/2 d5/2  44 S f7/2 p3/2 d3/2 s1/2 d5/2 42 Si d5/ d3/2 s1/2 14 d3/2 s1/2 d5/2 14 T NNERRE Modification of the shell structure at N=28

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

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

p3/2  f7/2 d5/2 s1/2 d3/ d5/2 s1/2 d3/ Ca p3/2  f7/2 d5/2 s1/2 d3/2 d5/2 s1/2 d3/ Ar J. Mrazek, S. Grévy et al, Very good agreement Expt. vs. SM up to 2 MeV. (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 /2- 3/2- 5/2- 1/2- 3/2- 7/2- 5/2- 1/2- SM (Nowacki) T NNERRE N=28 - complete spectroscopy of 44,45,46 Ar

Interest of heavy calcium isotopes 2 + levels systematic in even-even Ca isotopes Evidence of the semi-magic character of 52 Ca:  Shell closure at Z=20  Subshell closure at N=32: high E x of the 2 + state at 2.56MeV with a ( p 3/2 ) 3 -( p 1/2 ) 1 configuration How to get information on the position of the f 5/2 orbital ?  E x of the 4 + state in 52 Ca: ( p 3/2 ) 1 -( f 5/2 ) 1  E x of the 2 + state in 54 Ca: ( p 1/2 ) 1 - ( f 5/2 ) 1  discrimination between two interactions IR e S Frédéric PERROT  Different prediction on J  ground state for N>28 depending on the interaction  Inversion of the  s 1/2 -  d 3/2 orbitals Problematic of the potassium isotopes  decay of K→Ca: connection between the two problematics Characteristics of  decay for neutron rich nuclei :  large Q  window (~15 MeV in K) and low S n (~4 MeV)  high emission probability of 1 or 2 delayed neutron (P n ~40-90%) We need a very efficient neutron and gamma detection to perform  -  and  -n-  coincidences

September 2002 and July 2003 (Z=20) ISOLDE Experiments : IR e S

TOF spectrum from 52 K decay Fréderic Perrot IR e S

53 K decay: preliminary results IR e S in progress

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, 33 Mg, 34, 35 Al  Spectroscopy in the region of N=28 : 40, 41, 42 Si, 42,43,44 P, 44,45,46. S, 46,47. Cl  Spectroscopy in the region of Z  20: 51,52,53 K Mobility of TONNERRE  ISOLDE, GANIL (LISE)... T NNERRE …. Why not on SPIRAL low energy ? Need some minimum conditions………….

…..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, …  8 He ? T NNERRE 4) What experimental area ??? Background, area > 20 m 2 2) What intensity > LISE, SISSI, ISOLDE..???? > 1 pps,  (T 1/2 ) > 10 pps,  or  n > 100 pps,  or  n  3) What identification ????? Event by event, T 1/2, , 

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 T NNERRE COLLABORATION T NNERRE

at/s ISOLDE ANuclei Ga Rb Sr Kr at/s ISOLDE at/s ALTO ANucle i K Na Al Ni Cu Zn Sn at/s SPIRAL Yield information ISOLDE : Ulli Koster SPIRAL: radioactive_beams.htm ALTO : Fadi Ibrahim (preliminary estimation)