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
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
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
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.
・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)