-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

AZN

AZ+1N-1

Q

E

-deca

y

Sn

S2n

essential information to map the -strength function

comparisons with theorical predictions (Shell Model…)

complete--neutron spectroscopy

En access to the location and

structure of unbound levels

Exple: 11Li : Q=20.6 MeV Sn=0.7 MeV Pn~92%

When N>>Z : Q, Sn

-delayed neutrons emission dominant decay mode

E

A-1Z+1N-2

-n decay

A-1Z+1N-3

Eneutrons

TONNERRETONneau pour NEutRons REtardés

A new detector for Delayed-Neutron Spectroscopy(Collaboration LPC Caen - IFIN Bucarest)

First test in April 98 (GANIL)

•Up to 32 scintillators plastic bars

•En by TOF , 200 keV < En < 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. 412-423

SCINTILLATORS

T NNERRE

A. Buta et al, NIM A 455 (2000) 412-423

Array No. Of elements

R (m)

(%)

n

(%)2MeV

En

(keV)

n

(%) MSU 16 1.00 15 20 50 3 RIKEN « wall » 15 1.25 11 55 110 6 TONNERRE 32 1.2 45 44 103 19.8

TONNERRE STATUS

know better the region near"island of inversion" around N =20

24 6

810

1216

14

1820

2224

26

8

LiBeBC

NO

FNe

NaMgAlSi

N=20

HHe

E333: -n-decay of 32,33Mg and 34,35Al

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

33Al 34Al 35Al

2 hwexcitations

32Al

33Mg-1090

34Mg-685

31Na-502

32Na-1295

33Na-427

30Ne-698

31Ne-891

32Ne-128

32Mg-926

31Al

T NNERRE

- production of neutron-rich nuclei below 36Sby projectile fragmentation ( 78 MeV/A)

Be (target)- selection using the LISE3 spectrometer

32, 33Mg, 34, 35Al

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 windo

w

LepsLow energy neutron det

Si detector

Beam Time ~ 8 h

Intensity ~ 300 pps

19 modules of TONNERRE

GANIL: 2000

TOF(ns)

Beam Time ~ 12 hIntensity ~ 30 pps

12 little neutrons detectors

ISOLDE: 1999

TOF(a.u.)

34Aln

coïncidence

34Alone neutron

coïncidence

34Al

spectrum ( zoom)

34Al spectrum

34Al -nDecay

T NNERRE

T NNERRE

33Si

-n

MCSM

4+

2+

34Si

34Al

Sn = 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)

497043794255

3326

2133 ??

(3,4,5)-(3,4)-

3-2+

0

e+ e-C.E

.

11

93

02+ ???

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)

02

+

01

+

14351010

0

7/2-1/2+

3/2+

B. Fornal et al.,PRC 49 2413 (1994)

nEn (MeV)

3.572.642.091.731.230.86

Y. Utsuno et al.,PRC 64 011301R (2001)

Our results on the 32Mg -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 %)- ' 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)

nu

mb

er

of

co

un

ts

300 400 500 600 700 800 900

1000 1500 2000 2500 3000

energy (keV)- neutrons :

nu

mb

er

of

co

un

ts 350

300

250

200

150

100

50

40 60 80 100 120 140 160 180 200time of flight (ns)

1

23

4

5

6

7

1 4.51 MeV2 2.79 MeV3 1.78 MeV4 1.28 MeV5 973 keV6 680 keV7 370 keV

T NNERRE

33Al unknown low energy structure 32Al not pure usd

Before E333 experiment

What are the limits of the "island of inversion” ?

1+

M. Langevin et al., NPA 414 151 (1984)

33Mg

isomer 200ns

(3/2)+

32Mg-n

T 1/2= 90 (20) ms

(4+)

-n

2+

Pn=2.5 %

Pn=17.5 %

(4-)

T 1/2= 120 (20) ms

B. Fornal et al., PRC55 762 (1997)

M. Robinson et al., PRC53 R1465 (1996)

usd1+

2+

3 + 2 + 3 +1 + 2 +

4+

33Al

1+

M. Langevin et al., NPA 414 151 (1984)

33Mg

isomer 200ns

(3/2)+

32Mg-n

T 1/2= 90 (20) ms

(4+)

-n

2+

Pn=2.5 %

Pn=17.5 %

(4-)

T 1/2= 120 (20) ms

B. Fornal et al., PRC55 762 (1997)

M. Robinson et al., PRC53 R1465 (1996)

32Al E (keV)

4735 2894 2761 2364 2096 18381646 1617 1467 1046 594

n

C. Timis thesis LPCCaen T01-01 (2001)

•New -lines in the 33Al structure•Alimentation of 4+ and 4- levels in 32Al by -n decay of 33Mg

After

En (MeV)2.481.920.630.460.410.28

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

usd1+

1+

T 1/2= 86 (5) ms

not usd

T NNERRE

- t1/2 and Pn around 44S Sorlin et al. (GANIL)

- Mass measurement below 48Ca 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)054302

Z=20

Z=16

Z=14

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

14 16 18 20 22 24 26 28 30 32

Ca

S

Si

Number of neutrons N

S2n

(MeV

)

J. Reta

mosa

et a

l. PR

C5

5(1

99

7)1

26

6

• 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

d3/2s1/2d5/2

36S 2016

f7/2

p3/2

d3/2s1/2d5/2

44S 2816

d5/2

20

28

20

28

d3/2s1/2

14

d3/2

s1/2d5/2

16

- Hart. Fock + Bogol. (Péru et al.)

f7/2

p3/2

d3/2s1/2d5/2

44S 2816

f7/2

p3/2

d3/2s1/2d5/2

42Si 2814

d5/2

20

28

20

28

d3/2s1/2

14

d3/2s1/2

d5/214

T NNERRE

Modification of the shell structure at N=28

- production of neutron-rich nuclei below 48Caby 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

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

t1/2(39Si) = 47.52.0 msec

t1/2(40Si) = 33 1 msec

t1/2(41Si) = 20.02.5 msec

t1/2(42Si) = 12.53.5 msec

0

50

100

150

200

250

- 0.3 - 0.2 0 0.2 0.3

42Si0

50

100

150

200

25041Si

0

50

100

150

200

25039Si

0

50

100

150

200

25040Si

tim

e (

mse

c)ti

me (

mse

c)ti

me (

mse

c)ti

me (

mse

c)

déformation (2)-0.3 -0.2 0 0.2 0.3

QRPA39Si

40Si

41Si

42Si

exp.

exp.

exp.

exp.

- Are the Si isotopes deformed ?

T NNERRE

deformed

sphérical

t1/2 (Q-E*)-5

K. L

. Kratz and B

. Pfeifer

42Si

p3/2

20

28f7/2

d5/2

s1/2d3/2

14d5/2

s1/2

d3/220

48Ca2820

p3/2

20

28f7/2

d5/2

s1/2d3/2

d5/2

s1/2d3/2

20

14

46Ar2818

16

J. M

raze

k, S

. G

révy

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

420

13301240

1790

22602140

2420

7/2-

3/2-

5/2-

1/2-

3/2-

7/2-5/2-

1/2-

SM (Nowacki)

T NNERRE

N=28 - complete spectroscopy of 44,45,46Ar

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=20Subshell closure at N=32: high Ex of the 2+ state at 2.56MeV with a (p3/2)3-(p1/2)1 configurationHow to get information on the position of the f5/2 orbital ? Ex of the 4+ state in 52Ca: (p3/2)1-(f5/2)1

Ex of the 2+ state in 54Ca: (p1/2)1- (f5/2)1

discrimination between two interactions

IReS Frédéric PERROT

Different prediction on J ground state for N>28 depending on the interaction

Inversion of the s1/2-d3/2 orbitals

Problematic of the potassium isotopes

decay of K→Ca: connection between the two problematicsCharacteristics of decay for neutron rich nuclei : large Q window (~15 MeV in K) and low Sn (~4 MeV) high emission probability of 1 or 2 delayed neutron (Pn~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 :

IReS

TOF spectrum from 52K decay

Fréderic PerrotIReS

53K decay: preliminary results

IReS

in

prog

ress

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) ...

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, …

8He ?

T NNERRE

4) What experimental area ??? Background, area > 20 m2

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 – FranceN.L. Achouri, J. C. Angélique, G.Ban, S. Grévy, F. R. Lecolley, E. Liénard, N.

A. Orr, J. Peter and S. PietriIFIN – 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 - RussiaY. Penionzhkevich, S. Lukianov and O. Tarasov

GANIL - Caen – FranceF. de Oliveira, M. Lewitowicz, I. Stefan and C. Stodel

IPN – Orsay – FranceF. Ibrahim, D. Guillemaud Mueller, F. Pougheon, O. Sorlin

DAM – Bruyères le châtel J. M. Daugas, V. Meot and O. Roig

Univ. of Surrey - UKW. Catford and C. Timis

Nucl. Phys. Inst. – Czech RepublicZ. Dlouhy and J. Mrazek

T NNERRE COLLABORATION

T NNERRE

at/s

ISOLDEANuclei

40062Ga

2.10374Rb

5

4.103

2.105

9.2.105

75

76

77

78

Sr

3.5

3.103

5.105

2.106

1.8.107

71

72

73

74

75

Kr

4 - 6.108

3.107

4.106

2.105

6.103

2.102

3.2.107

2.106

2.104

4.104

4.103

4.102

1

4.104

2.104

2.6

8

40

2

5.4.105

7.4.104

9.103

1.2.103

4

at/s

ISOLDE

1.2.106

5.9.105

2.105

2.104

2.104

2.103

2.102

2.104

1.104

at/s

ALTOANuclei

49

50

51

52

53

K

33

34Na

34

35Al

69

70Ni

76

77

78

79

Cu

76

78

80

Zn

128-132

133

134

135

136

137

Sn

at/s

SPIRAL

2.102

3-6.103

1.5.104

4.105

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)