Beta decay around 64Cr

GANIL, March 25th 2010

62V 63V 64V60V 61V

63Cr 64Cr 65Cr61Cr 62Cr60Cr

64Mn 65Mn 66Mn

65Fe 67Fe 1) 2+ in 64Cr

N=40

2) Isomers in 64,66Mn

66Fe

3) 0+2 in 66Fe and isomers in 63,65Cr.

Collectivity in neutron rich N=40 nuclei

decay 64V->64Cr.64,66mMn produced via fragmentation: decay via and e-.

If low lying 0+2 state=> might be isomer.

Isomers present in all N=39 and 41 isotones (from Z=28),why not observed at Z=24?

Experimental method

D2D1

86Kr58Mev.u

4Ae

58Ni : 105m

C

1) Production : 86Kr + 58Ni (Lise target Pos.)

Be : 200 m

2) Selection : LISE Spectro. + Slits + Wedge

Caviar

E; DSSD

E ; Si

3) Identification : B (caviar) + E-E + E-ToF 4 Ge-detectors4) Detection - : DSSD + Ge detectors

Flight Path : From Lise target to 1st focal point 200ns (T1/2~70ns)

Detection : 1) -decay from isomeric states (produced via fragmentation) 2) -decay of the implanted ions (position correlations in the DSSD) 3) -decay (prompt/delayed) following the -decay

Production rates

62V 63V 64V60V 61V

63Cr 64Cr 65Cr61Cr 62Cr60Cr

64Mn 65Mn 66Mn

65Fe 67Fe

N=40

66Fe 3x10-4pps

1x10-2pps

2x10-1pps

Low stat. Experiment: Need for as clean as possible data (bckgd issue).

Few counts per second expected (<10) => Difficulty to make sure tuning is ok.*) 1st run on 64Mn. (up to 10-20pps)?*) Then move on 64V (20Ut’s = 230 counts => about 10 ’s).

Tuning of Lise MUST be quick.

Data analysis

1) Particle Id.2) calibrated.3) Implantation profile in DSSD4) Timing (either following or HI)

No need for half-life reconstruction online (not possible?).

Online

Online + half-life reconstruction.

Offline

Acq electronics

1) Caviar

2) Si detectors: 64 Strips => 2ADCs

3) 4 Ge (among which 1 Clover) => 7 Chan.

4) Timing e-: Centrum + SMC (beam on/off)

5) Timing : TAC (1µs)

6) Scalers for Si & Ge

3 ADC1 TDC2 U2M

Everything in D4 => Noise + Number of chan.

Logic (General)

Si 500µSingle Sided

Si 1500µDouble Sided

Si 1000µSingle Sided

*) Implant.: 1.5GeV Preamp. 2mV/MeV

=>Provides Eion + Yion+ saturation on Xi

E. 1.5GeVRear face(Trig1)

*) Up to 1MeV MaxReset Preamp. 200mV/MeV

=>Provides Ee- + X

(Trig2)

=> Provides Y => Provides Y

Logic (Electronic)Triggers: E + DSSD

Read E & time of Ge for each trigger.

Electronics for HI: standard.

Electronics for

1500µReset pream (14MeV)Reseting time: 20µs.

200mV/MeVSpectr. Ampli

Caen (16 Chan)Out E ADC

OutE *10

Linear fifoSignal inversion?

Low Thresh. Discri.

500µ1000µ

Ge

ADC

Nuclear Structure Towards 28Ni50 (Exp.)

f7/2

f5/2p3/2

g9/2

Z=28

N=40

N=50

Cu isotopes (N>40) :1 proton outside Z=28 core interacting with g9/2 neutrons

Towards N=50 filling of the g9/2 orbits10 neutrons interacting with fp orbitals

S. Franchoo et al. PRL 81, 3100 (1998)

Inversion of f5/2-p3/2 states?

Search for low lying states in 75,77Cu.

75Cu 77Cu

Need of experimental evidences on the crossing of f/2 – p3/2 orbits

Nuclear Structure Towards 28Ni50 (Theo.)Structure of Cu isotopes :

Recent theoretical interest : Shell Model and Mean Field

N. A. Smirnova et al., PRC69, 044306 (2004) A.F. Lisetskiy et al., PRC70, 044314 (2004)EPJA25, s01,95 (2005)

SHELL

MODEL

MEAN

FIELD

T. Nikšić et al., PRC71 (2005) 014308

Depending on the model/approachcrossing 3/2-

1 – 5/2-1 in 73Cu to 79Cu…

Nuclear Structure Towards 28Ni50

> 1s< 1s< 200ns

66Mn 67Mn 68Mn

68Fe 69Fe 70Fe

69Co 70Co 71Co 72Co

71Ni 72Ni 73Ni 74Ni73Co

67Fe

73Cu 74Cu 75Cu 76Cu 77Cu 78Cu 79Cu

81Zn77Zn 78Zn 79Zn 80Zn

82Ga80Ga 81Ga

Z=28

N=5071Fe

72Cu70Ni69Ni

79Ga78GaPossibleisomer

74Co

75Ni 76Ni 77Ni 78Ni

T1/2

Experimental difficulties : 1) Numerous isomeric states 2) Low production rates

As compared to Daugas et al.- Tuned for more exotic species- Beam twice more intense- Improved -efficiency

- decay selection rules- Sensitive to isomeric states- Population of 5/2- and 7/2- states (among others)

Proposed experiment : -spectro.

J.-M. Daugas PhD thesis@GANIL (1999)86Kr on Ni target

75Cu :• Isomeric states• -spectroscopy only• No spin assignments

Coun

ts

E

75Cu

Triggered other studies : -decay or isomers Phys. Rev. C 68 (2003) 044304 – -decay 72Co

Eur. Phys. Journ. A 20 (2004) 109 – Isom. 76Ni Eur. Phys. Journ. A 22 (2004) 455 – -decay 71,73Co

Publi. :Phys. Lett. B 476 (2000) 213 – 78Zn

Beam Time Request

Structure of transmitted nuclei

- decay half-lives (New *, Improved )-Isomeric states (T1/2, J)

- States fed via -decay (J)

Deduced level schemes using -coincidences 21 UT’s required

+3 UT’s for identification & calibrations Total : 24 UT’s

- Isom

75Cu 1115 110 67576Cu 1570 155 95077Cu 890 90 61075Ni 360 36 21576Ni 76 7 4577Ni 9 - 5

66Mn 67Mn 68Mn

68Fe 69Fe 70Fe

69Co 70Co 71Co 72Co

71Ni 72Ni 73Ni 74Ni

73Co 74Co

75Ni76Ni 77Ni

67Fe

73Cu 74Cu 75Cu 76Cu 77Cu 78Cu 79Cu

78Ni

81Zn77Zn 78Zn 79Zn 80Zn

82Ga80Ga 81Ga

Z=28

N=50

71Fe

≥3.10-1 pps

1-3.10-1 pps

10-2-10-1 pps

10-3-10-2 pps

Rates

~85% (measured)~10% @ 500keV (simulated)feeding 5% (assumed from systematic)

*

*Lower limits

Spectroscopy of Cu isotopes

-decay of Ni isotopes

Direct feeding of 5/2- and 7/2- states+

side feeding from higher lying states

Observed -transitions ~ 0.5 – 1.0 MeV

Isomer in 77Cu?

HFB-D1S + blocking : Cu isotopes

3/2-5/2-

Experiment3/2-5/2-

Theory

?

69 71 73 75 77 79 81 A83

Gamma efficiency

Geant4 Simulations [B. Rossé]

Energy [keV]

Efficiency [%]

10

5

20

Config. Daugas et al.2 Coax + 1 Clover + 1LEPS

Proposed Config.3 Coax + 1LEPS + 00 Coax

Enhanced efficiency up to 150keV.Expected efficiency below 150keV : at least same as Daugas et al.

Experimental details

E

E

Implantation Strip

Correlation Strips

1- E-E + E-TOF : Id

2- Spatial correlations -Ion: bckgd subtraction

3- Time correlations : line assignment