Coulomb excitation experiments at JAEA (Japan Atomic Energy Institute)

JAEA, Chiba Inst.Tech.a, Kyusyu Univ.b, Hiroshima Univ.c,

KEKd

M. Koizumi, Y. Toh, M. Oshima, M. Sugawarab A. Kimura, A.

Osa, Y. Hatsukawa, T. Morikawab, K. Furutaka,

F. Kitatani, H. Harada, S. Nakamura, N. Imaid, H. Miyataked,

Y. Kojimac

GOSIA work shop 2008/4/8-10 Warsaw, Poland

Japan Atomic Energy Agency

Contents

1. Introduction - Coulomb excitation experiments at JAEA

with GEMINI-II and LUNA -

2. Coulomb excitation experiments at JAEA2.1 Ge isotopes2.2 66,68Zn2.3 132Xe (some problems encountered)

3. Plan for nuclear structure studies with RI beams at TRIAC facility of JAEA

4. Summary

Negative IS

Tandem acc. (18MeV)

Booster acc.

ECR IS

Tandem-booster accelerator facility of JAEA

JAEA tandem-booster accelerator

• Negative ion source, and ECR ion source can provide various ion beams.

• Particles energies are enough for Coulomb excitation experiments.

• Good beam quality, i.e., 1~2 mm in diameter on target

H He

Li Be B C N O F Ne

Na M g Al Si P S C l Ar

K C a Sc Ti V C r M n Fe C o Ni C u Zn G a G e As Se Br Kr

Rb Sr Y Zr Nb M o Tc Ru Rh Pd Ag C d In Sn Sb Te I Xe

C s Ba La Hf Ta W Re O s Ir Pt Au Hg Tl Pb Bi Po At Rn

Developed

：Under developm ent

En

erg

y

mass (A)

Tandem-booster

Tandem only

GEMINI-II - a Ge detector array --An apparatus for Coulomb excitation experiments, for -

coincidence experiments, and for other applications -

16 Ge detectors (with BGO-ACS) and 3 LOAX detectors

LUNA - a position sensitive particle detector array -

Characteristics of LUNA

1. applicable for high event rate (up to 105 cps)

2. good positional resolution: 0.5 – 1.0 mm

3. high resistance to radiation damage

4. compact (if one compare to a gas counter)

5. easy to handle

Beam

Contents

1. Introduction - Coulomb excitation experiments at JAEA

with GEMINI-II and LUNA -

2. Coulomb excitation experiments at JAEA2.1 Ge isotopes2.2 66,68Zn2.3 132Xe

3. Plan for nuclear structure studies with RI beams at TRIAC facility of JAEA

4. Summary

2.1 Ge isotopes

2. Recent study of Coulomb excitation experiments at JAEA

(N=40)

In order to study the structural evolution of the 02+ state, we

carried out multiple Coulomb excitation experiments.

Matrix elements → Quadruple Sum Rule → <Q2>s

01+

02+

Isotope dependence of <Q2> of Ge

Deformed

Spherical

The shapes of Ge isotopes

(N=40)

The spherical 02+ intruder state of 70Ge becomes the 01

+ state of 72,74,76Ge and vice versa. This may be due to the appearance of

an effect of high spin orbit (1g9/2).

Spherical

Deformed

Contents

1. Introduction - Coulomb excitation experiments at JAEA

with GEMINI-II and LUNA -

2. Coulomb excitation experiments at JAEA2.1 Ge isotopes2.2 66,68Zn2.3 132Xe

3. Plan for nuclear structure studies with RI beams at TRIAC facility of JAEA

4. Summary

62 64 66 68 70 72 740

500

1000

1500

2000

2500

3000(4+

1)

2+

42+

3

(4+

1)

(2+

1)

0+

3

4+

24+

2

0+

3

0+

2

4+

1

2+

2

2+

1

0+

1

Energy [keV]

M ass num ber of Zn

Coulomb excitation experiments of 30Zn isotopes

66Zn 68Zn IBM ARM

--------------------------------------------------------------------------------------

B(E2) [efm2] exp. SM [9] exp. SM [9] O(6) =30o

11 02 228 (18) 270 (4) 258 (16) 270 (40) 1.0 1.0

12 02 0.06 (28) 0.5 (10) 9.5 (8) 8 (5) 0.0 0.0

13 02 2.3 (4)

12 20 83 (13) 29 (4)

12 22 650 (228) 260 (40) 304 (62) 350 (50) 1.4 1.4

13 22 157 (45) 10 (3)

11 24 278 (11) 330 (50) 216 (7) 280 (40) 1.4 1.4

22 02 125 (90) 1.2 (4)

23 02 287 (23)

21 24 107 (34) 9.4 (13)

Q(21+) [efm2] +24 (8) -19 +9 (3) -62 (17)

Shell Model: J.F.A. Van Hienen, et al., Nucl. Phys. A269 (1976) 159.

Model space: 56Ni core + (2p3/2 1f5/2 2p1/2)

Results of the Coulomb excitation experiments of 66,68Zn

Structure of 68Zn

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Ex

cit

ati

on

En

erg

y [

MeV

]

42

+

6(2) 22

+

(61

+)

8 (

5)

5.0 (8)

10 (3

)

0.5

8 (

5)

17

.4 (

14

)

18 (4

)13

.1 (

4)

15

.8 (

10

)

0.1

4 (

2)

01

+

02

+

21

+

23

+ 41

+

[w.u.]1

3.1

(4)

Q(21+) = 0.09 (3) eb

intruder

triaxial or -unstable deformation

Shell Model (56Ni+ (2p3/2 1f5/2 2p1/2)) does not reproduce the excitation

energies and B(E2)s relevant to the 02+ and 23

+ states.

=> those levels are influenced by the 1g9/2 orbit

0.0 0.1 0.2 0.3 0.4

60o

0o

68Zn

0.0 0.1 0.2 0.3 0.4

60O

0O

2

66Zn

66Zn

Potential Energy Surfaces of 66,68Zn calculated with Nilsson-Strutinsky model

First minima

Second minima

0.0 0.1 0.2 0.3 0.4

60o

0 1.0 2.0 3.0 4.0 5.0

0o

Energy [MeV]

1g9/2 neutron orbit

68Zn

0.0 0.4 0.0 0.4

2 2

0.20.2

0O0O

60O60O

The 02+ bands of 66,68Zn may stand

on the second minima.

Contents

1. Introduction - Coulomb excitation experiments at JAEA

with GEMINI-II and LUNA -

2. Coulomb excitation experiments at JAEA2.1 Ge isotopes2.2 66,68Zn2.3 132Xe (some problems encountered)

3. Plan for nuclear structure studies with RI beams at TRIAC facility of JAEA

4. Summary

0

500

1000

1500

2000110 120 130 140 150

110 120 130 140 1501.0

1.5

2.0

2.5

3.0

E(4+)

Excitation Energy [keV]

E(2+)

N = 82

M ass Num ber

E(4

+)/E(2

+)

54Xe： Z = 50 + 4

qusi-rotational ? A~120

↓

-unstable ? A~130

↓

vibrational ? A=134

↓

particle excitation ? A=136 (N~82)

↓

to be studied with RNB A > 136

Shape phase transition in Xe isotopes

124-130Xe can be considered to be

-unstable nuclei because of the

similarity in excitation energies of

O(6) nuclei.

A E(5) critical point can exist

same where -unstable nuclei

become spherical nuclei.

Coulomb excitation experiment of Xe

0 1000 2000 3000 40001

10

100

1000

10000

27 Al (2211)

27 Al (1014)

Counts

C hannel [0.5 keV/ch]

40 K (1461)

27 Al (844)

668

630

772

1298

0. 0

843. 761014. 45

2211. 1

5/ 2+

1/ 2+3/ 2+

7/ 2+

27Al

0. 0

667. 720

1297. 919

1440. 32

0+

2+2+4+

132Xe

Incident beam：132Xe（27.0%）400MeV 0.6pnA

Target：Al

A Spectrum observed in 132Xe Coulomb excitation experiment

Systematic study of -unstabel nuclei and shape phase transition

0 20 40 60 800

5

10

15

Scattering angle of projectile

in Labo. fram

e [deg.]

R ecoiled angle of target in Labo. fram e [deg]

~50o

0 20 40 60 800

50

100

150

200

250

Kinetic Energy [M

eV]

lab. [deg.]

132Xe (400 MeV) + 27Al

Al

Recoiled angle of target [deg.]

0 20 35 50 65

6.5 10.2 11.8 10.2

Scattering angle of projectile [deg.]

0.0

Re

co

ile

d a

ng

le o

f ta

rge

t [d

eg

.]

(lab. frame)

2D recoiled Al angular

distribution of a position

sensitive particle detector

Problems in GOSIA analysis

Recoiled target detection in inverse kinematics

-> OP, INTG command seems always to take the larger CM angles.

beam beam

target

detectorOP, INTG:

This option includes

integration over solid

angle of the particle

detectors, ….

Laboratory frame

labo

labo

vG

cm(1)

cm(2)

Input parameters

…

mini, max :

detected particle in the

labo. frame

…

1, … NT :

projectile scattering

angles in the labo. frame

…

vcm

Yield data fort.3 is converted to fort.4 with

“OP, INTG” option. Correction of finite seize

of detector is included in the fort.4 data.

Encountered problems in analysis with GOSIA

1. OP, INT (Integration)

Recoiled target detection in inverse kinematics.

2. GOSIA-2

GOSIA-2 was also used for fitting 27Al and 132Xe data, but we do not obtain 2-minimum with reasonal MEs, yet. (It seems to take some time to learn.)

3. Finding 2 minimum

Some of MEs are not sensitive to 2.

Such MEs sometimes disturb 2-minimum finding procedure.

4. Visualization, GUI

We sometimes make mistakes when we making input files.

GUI or some tool would be helpful.

Contents

1. Introduction - Coulomb excitation experiments at JAEA

with GEMINI-II and LUNA -

2. Coulomb excitation experiments at JAEA2.1 Ge isotopes2.2 66,68Zn2.3 132Xe

3. Plan for nuclear structure studies with RI beams at TRIAC facility of JAEA

4. Summary

JAEA-ISOL

1.4 MeV/u beam line

36-MeV 3- A P beam + U target

3. Plan for nuclear structure studies with RI beams at TRIAC facility of JAEA

We will extend our systematic study with Coulomb excitation

method towered unstable nuclei at TRIAC (low-energy radio

active beams facility).

TRIAC (Tokai Radioactive Ion Accelerator Complex)

Tokai/JAEA

TRIAC facility ion source of TRIAC-ISOL

IH-linac

SCRFQ-linac

18-GHz ECRIS type charge breeder

ECR-CB

SCRFQ

IH

Ion sources

FEBIAD

Surface Ionization

Proposal for upgrading TRIAC facility

GEMINI-II

Contents

1. Introduction - Coulomb excitation experiments at JAEA

with GEMINI-II and LUNA -

2. Recent study with Coulomb excitation at JAEA2.1 Ge isotopes2.2 66,68Zn2.3 132Xe

3. Plan for nuclear structure studies with RI beams at TRIAC facility of JAEA

4. Summary

Summary* Coulomb excitation experiments at JAEA have been introduced.

* Some of our studies were given:

- Ge: Shape coexistence, and shape exchange

between the 0+ states in the increase of

neutron numbers are found.

- Zn: The 02+ states are probably effected by the

1g9/2 orbit.

- 132Xe: Analysis is in progress.

* One of our future plan with an RI beam facility

was shown.

Some problems encountered in analysis were also shown.

終わり

・Small solid angle

=> Small Doppler shift

・High detection efficiency

25-70% Ge detectors

(relative to 3" NaI scintillation detector)

=> total efficiency is about 1.2%

・Low background

=> high peak to Compton ratio are

realized with the BGOACS

GEMINI-II

Side view

Top view

Ge detectors with BGOACS：16

LOAX：3

R.F. Casten et al., Phys. Lett. 152 (1985) 22.

124-130Xe can be considered to be -unstable nuclei because of

the similarity in excitation energies of O(6) nuclei.

F. Iachello, Phys. Rev. Lett. vol85, 3580 (2000)

Potential energy surfaces

O( 6)

U( 5) SU( 3)

Rot orVi br at or

E( 5)

X( 5)

- unst abl e

IBM model

Symmetry triangle

From -unstable shape to spherical shape

spherical

0 20 40 6045

50

55

-0.3 0.0 0.345

50

55

0 20 40 60

7/2[303]

1/2[321]

7/2[413]

5/2[422]

3/2[431]

1/2[301]

5/2[303]1/2[440]

3/2[301]

3/2[312]

1/2[310]

= 0.18

[degree]

7/2[303]

1/2[431]50

28

Sin

gle

-Part

icle

En

erg

y [

MeV

]

= 0o

2

1g9/2

2p1/2

1f5/2

2p3/2

9/2

[404]

7/2[413]

5/2[422]

3/2[431]

1/2[440]

1/2[301]

5/2[303]

3/2[301]

1/2[310]

3/2[312]

1/2[321]

1/2[301]

9/2[404]

3/2[431]

5/2[422]

7/2[413]

1/2[440]

5/2[303]

3/2[301]

1/2[310]

3/2[312]

1/2[321]

= 0.10

[degree]

Neutron single-particle energies

36 36 36

3838 38

The 02+ of 66,68Zn may influenced

by 1g9/2 orbit.

Proposals at TRIAC facility

• Diffusion of 8Li in materials (Material Sci.)

• Measurement of nuclear reaction cross sections of 8Li (Nuclear Astrophysics)

• Polarized RI beam production with tilted foil method for magnetic moment measurement with -NMR (Nuclear Physics)

• Coulomb excitation (Nuclear Physics)

35 40 45 50 55 60 65

36Kr

46Pd

44Ru

42M o

40Zr

38Sr

<r2> [fm

2]

N eutron Num ber

37Rb

501 fm 2

* Q-moment measurements of Sr and the others