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Oct. 24, 2011
DCEN2011
Experimental project for production of
neutron-rich nuclei by multinucleon
transfer reaction (KISS project)
Y.X. Watanabe (KEK) for KISS collaboration
Collaborators
KEK
RIKEN
K.U. Leuven
H. Miyatake, S.C. Jeong, H. Ishiyama, N. Imai, Y. Hirayama,
K. Niki, M. Okada, M. Oyaizu, Y.X. Watanabe
M. Wada, T. Sonoda, Y. Ito, Y. Matsuo
P. Van Duppen, Y. Kudryavsev, M. Huyse
1
Astrophysical nucleosysnthesis by r-process
H. Grawe et al., Rept. Prog. Phys. 70 (2007)1525.
N=126
N = 126 (Waiting point)
Z
N = 82
Nuclear characteristics (T1/2, Sn, …)
Better understanding of r-process scenario
Fe
N
A half of elements heavier than Fe is
• Actual
considered
to ber-process
producedpath
by rapid
Astrophysical
Nn(r-process)
-T condition
neutron •capture
process
Lifetime measurements around N=126
→ Astrophysical environments of r-process
• Duration time passing through waiting point
• Actinide element production rate
2
Lifetime measurements around N=126 nuclei
atomic number
83
209Bi
82
204Pb
206Pb 207Pb 208Pb
81
203Tl
205Tl
207Tl
198Hg 199Hg 200Hg 201Hg 202Hg
204Hg
206Hg
5×108 years ≤ T1/2
205Au
30 days ≤ T1/2 < 5×108 years
80
196Hg
79
197Au
78
194Pt
77
193Ir
203Ir
76
192Os
202Os
195Pt
196Pt
198Pt
204Pt
75
201Re
74
200W
10 minutes ≤ T1/2 < 30 days
T1/2 < 10 minutes
unknown
116 117 118 119 120 121 122 123 124 125 126
neutron number
• five-year project since FY2010: Lifetime measurements of N=126 nuclei
• Multinucleon transfer (MNT) reaction to access N=126 nuclei
C.H. Dasso et al., Phys. Rev. Lett. 73 (1994) 1907.
V. Zagrebaev and W. Greiner, Phys. Rev. Lett. 101 (2008) 122701.
L. Corradi et al., J. Phys. G: Nucl. Part. Phys. 36 (2009) 113101.
• From 203Ir down to 200W by 136Xe+198Pt MNT reaction
3
KEK Isotope Separation System (KISS) @ RIKEN
Detection system
- 3 detection stations
- Tape-transport system
- Multi-layered plastic scintillators
- Ge detectors
- Lifetime measurements
- b-decay spectroscopy
Focusing chamber
- Electric-Q triplet
- Electric deflector
- Slit
- Monitors
Extraction chamber
- Electric lens
- Monitors
ISOL (Ion Separator On-Line)
- Electric-Q doublet
- Magnetic dipole
- Magnetic-Q doublet
Gas catcher system
- Target (iso-pure 198Pt)
- Gas cell (Ar gas)
- Laser resonance ionization
- SPIG (SextuPole Ion Guide)
4
MNT reactions
Points of project
Aimed reaction channels are very rare.
• Estimation of
Absolute cross sections
Isotopic distribution
are very important subjects
from theoretical and experimental point of view
• Small production yields as well as short lives
Gas catcher system
Efficient collection
Fast extraction
Low background detection system
→ Efficient measurements
• A lot of contaminants
Laser resonance ionization → Isotopic separation (Z)
ISOL
→ Mass separation (A)
Gas catcher system
— Laser resonance ionization + ISOL —
P. Van Duppen, Nucl. Instrum. Meth. B126 (1997) 66.
Yu. Kudryavtsev et al., Nucl. Instrum. Meth. B267 (2009) 2908.
Ar gas
SPIG (SextuPole Ion Guide)
Gas cell filled with
0.5 atm. Ar gas
gas flow
Laser resonance
ionization
(Z selection)
+
+
+
Beam
diameter : ̴ f1 mm
emittance : ̴ 10p mm · mrad
+
ISOL
(A separation)
198Pt
136Xe
9 MeV/A
2nd chamber
6×10-2 Pa
TMP
1600 L/s
Ion source chamber
37 Pa
Screw Pump
175 L/s
VRF
VSPIG
V0 ̴ 60 kV
Extraction chamber
10-5 Pa
TMP
1500 L/s
̴
Separations of Z and A are achieved by laser
resonance ionization and ISOL, respectively.
6
Gas cell design
- Efficient collection and rapid extraction -
f10 cm
3 cm
(mm)
Ar gas
0.5 atm.
Cross-sectional view of
stopping distribution (202Os fragments)
extracted yields (a.u.)
Calculated transport time profile
160
120
80
40
0
200
0
198Pt
0 1 2 3 4 5 cm
target
136Xe
beam
ion collector
exit hole
electrode
(f1 mm)
Stopping efficiency : estop = 87 %
Simulation by hydrodynamic calculations
survival probability
Ar
gas
800 1000 1200 1400
Mean transport time = 253 ms
Transport efficiency : etra = 56%
laser
laminar flow
600
transport time ( msec )
(mm)
Top view of gas cell
400
Evaluated survival probabilities
of radioactive nuclei
1.0
0.8
0.6
0.4
0.2
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
half-life (sec)
Survival probability : esur = 72%
7
(T1/2 = 500 msec)
Laser resonance ionization
- Element selection Schematic diagram of laser system setup
Frequency tunable
dye lasers
dye laser
ScanMate2E
excimer laser
LPX240i
excimer laser
LPX240i
dye laser
FL3002
atomic energy levels
(extracted fragment)
autoionizing state
(AIS)
l2
laser
Intermediate state
laser
l1
Gas cell
l2
Combination of two laser wavelengths for
ionization is intrinsic to each element
ionization
EI
Ex
l1
g.s.
Z selection
Stable isotopes (Z = 69–78)
l1 : 210 – 450 nm
l2 : 350 – 660 nm
l1 and l2 tuning
for the most efficient ionization-schemes
of radioactive isotopes
Detection station
Ge detectors for X rays
(eX = 60%
for 70 keV X-ray)
Detection system
Tape transport system
200W
: production rate = 0.11 pps
~1 × 104 particles/day
Plastic scintillators
for b rays (eb = 80%)
b-decay detection rate: ~160 counts/day
Lifetime with 10% error
3rd
1st 2nd
Limitation of lifetime measurements
T1/2 (predicted by KUTY)
Au
1 day
Pt
Ir
Ge detectors for g rays
(eg = 20%
for 500 keV g-ray)
Re
Beam-on/off time-sequence
1st
beam
station
on
beam
off
switch
2nd
beam
station
on
0.5 s
tape movement
(50cm)
beam
off
beam
on
Ton = T1/2 × 2
Toff = T1/2 × 3
beam
off
beam
on
switch
switch
3rd
beam beam
off
station on
beam
off
beam
on
200W
W
Ta
waiting nuclei
Toff
Ton
1h
Os
Hf
Lu
Yb
beam
off
120 121 122 123 124 125 126
N
1 min
1s
0.1 s
10 ms
9
Multinucleon transfer (MNT) reaction
64Ni
(6.1 MeV/A) +238U
L. Corradi et al., Physical Review C59 (1999) 261.
projectile-like fragments
-5p
-6p
Experimental data
-4p
-3p
-2p
-1p
0p
6n pick-up
Calculations (GRAZING code)
A. Winther, Nuclear Physics A572 (1994) 191;
A. Winther, Nuclear Physics A594 (1995) 203.
• Rather large cross sections (~1 mb) for 6p-stripping channels
• Up to 6n-pick-up channels for pure neutron transfer (0p)
10
Production distribution
@ 7 MeV/A
s (mb)
104
s (mb)
104
10
198Pt
1
78
10-1
76
10-2
114 116 118 120 122 124 126
Neutron number
136Xe+208Pb
82
80
78
76
74
@ 7.3 MeV/A
208Pb
80
10-4
10-4
114 116 118 120 122 124 126
Neutron number
10-2
10-3
208Pb
10-4
s (mb)
104
103
102
10
10-3
10-1
76
82
102
10-2
1
114 116 118 120 122 124 126
Neutron number
103
10-1
10
198Pt
78
s (mb)
104
1
102
74
10-3
74
Atomic number
evaporation
evaporation
Atomic number
Atomic number
102
80
103
82
103
82
Atomic number
136Xe+198Pt
80
78
76
74
114 116 118 120 122 124 126
Neutron number
10
1
10-1
10-2
10-3
10-4
11
Excitation functions and yields
Excitation functions
for production of N = 126 isotones
Expected yields for N = 126 isotones
102
202Os
201Re
10-2
200W
10-3
199Ta
10-4
198Hf
10-5
10-6
202Os
10
197Lu
5
6
7
8
9
10 11 12 13
Elab (MeV/A)
s ~ 0.1 mb for 202Os
s ~ 1 mb for 200W
calculated by GRAZING code
(http://personalpages.to.infn.it/~nanni/grazing)
Yield (pps)
cross section
after evaporation (mb)
10-1
1
10-1
200W
Measurement
limit
10-2
10-3
10-4
10-5
136Xe
: 9 MeV/A, 2 pnA
198Pt
: 12 mg/cm2
196 197 198 199 200 201 202 203 204
Mass (A)
5.0 pps for 202Os
0.1 pps for 200W
12
beam
198Pt
target
MNT with RIB
10
83
82
81
80
79
78
77
76
75
74
73
72
71
198Pt
Atomic number
83
82
81
80
79
78
77
76
75
74
73
72
71
-5
-10
-15
-20
-25
116 117 118 119 120 121 122 123 124 125 126
144Xe
0
beam
Atomic number
5
-30
5
0
-5
-10
-15
-20
-25
Neutron number
10
208Pb
5
0
-5
-10
-15
-20
-25
-30
Neutron number
10
116 117 118 119 120 121 122 123 124 125 126
target
83
82
81
80
79
78
77
76
75
74
73
72
71
Neutron number
198Pt
208Pb
116 117 118 119 120 121 122 123 124 125 126
-30
Atomic number
Atomic number
136Xe
83
82
81
80
79
78
77
76
75
74
73
72
71
10
208Pb
5
0
-5
-10
-15
-20
-25
116 117 118 119 120 121 122 123 124 125 126
Neutron number
-30
Atomic number
136Xe+198Pt
@ 7 MeV/A
+ 198Pt : Cross sections
s (mb)
104
82
103
80
102
198Pt
78
10
1
76
10-1
74
10-2
72
10-3
10-4
118 120 122 124 126 128 130
Neutron number
144Xe+198Pt
Atomic number
144Xe
@ 7.2 MeV/A
s (mb)
104
82
103
80
102
198Pt
78
10
1
76
10-1
74
10-2
72
10-3
10-4
118 120 122 124 126 128 130
Neutron number
14
140, 144Xe
+ 198Pt : Yields
Expected yields of N=126 isotones
(E~9 MeV/A, optimized target thickness)
Expected beam intensities of Xe isotopes
(Proton-induced fission of U
at the total fission rates of 1014 Hz)
104
1011
Beam intensity (pps)
e = 0.01
108
107
144Xe
106
102
Yield (pps)
140Xe
109
Measurement
limit
105
104
103
136 138 140 142 144 146
Mass (A)
198Hf,
waiting nuclei
1
144Xe+198Pt
10-2
10-4
10-6
194
(Er)
196
(Yb)
198 200
(Hf) (W)
Mass (A)
202
(Os)
204
(Pt)
one of the waiting nuclei, would be accessed by using RIB 140Xe
15
Understanding of MNT reactions
58Ni
+ 208Pb
( L. Corradi et al., Phys. Rev. C66 (2002), 024606. )
Isotopic distributions of PLFs (proton stripping channels)
calculation
-6p
-5p
-4p
50 60
50 60
50 60
50 60
-3p
-2p
-1p
0p
50 60
50 60 50 60
Mass number
50 60
50 60
50 60
50 60
50 60 50 60
Mass number
50 60
50 60
50 60
50 60
50 60 50 60
Mass number
50 60
50 60
Independent
single-nucleon transfer
modes
+ one pair transfer
mode
+ particle evaporation
For better description
Absolute cross sections ← Pair transfer
Isotopic distributions
← Energy dissipation (Evaporation)
16
Experiment with VAMOS at GANIL
198Pt
(1.3 mg/cm2)
VAMOS
EXOGAM
~ grazing
angle
12 (or 11) clovers
Suppression shield configuration B
with full Compton suppression
TLF
g-rays ~500 keV
total photo-peak efficiency ~10%
• MWPC
• Drift Chambers 2
• Ionization Chamber
• Silicon Wall
PLF
Trajectory
Path length, Angles, Br
Velocity
Total kinetic energy
Mass, Atomic number, Charge
17
Cross section measurements for 136Xe + 198Pt
Cross sections to produce PLFs and TLFs by MNT reactions of 136Xe+198Pt
s (mb)
PLF
s (mb)
TLF
4p pick-up
198Pt
136Xe
3p pick-up
g-transitions are known (Z=75~77)
Calculated by GRZAING code ( A. Winther, program GRAZING, http://personalpages.to.infn.it/~nanni/grazing ).
• PLF : fragments are detected by VAMOS (s > 1 mb ↔ 4-proton pick-up channels)
• TLF : g-rays are detected by EXOGAM (s > 10 mb ↔ 3-proton pick-up channels)
Unknown g-decay scheme
Systematic tendency of gamma transitions over isotopic chains
New isotope 202Os
18
Summary
•
Investigation of astrophysical environment of r-process
Lifetime measurements for nuclei around N=126
•
Nuclear production by MNT reactions of 136Xe+198Pt
Rare events, Large contaminants
•
KEK Isotope Separation System (KISS) at RIKEN
Gas catcher system : Efficient collection, Fast Extraction
Laser resonance ionization + ISOL : Z & A separation
Low-background detection system : 10% error for 200W
•
Nuclear production by MNT reactions with neutron-rich RIB
198Hf,
•
one of waiting nuclei, would be accessed by using RIB 140Xe
Better description of MNT reactions
Pair transfer, Energy dissipation
Absolute cross sections and isotopic distributions
will be measured by VAMOS at GANIL for 136Xe+198Pt system
20
Q-value
21
Contaminations
+ 198Pt
198Pt
202Os
Isobaric distribution (A=202)
s (mb)
s (mb)
atomic number
136Xe
~99.7%
contaminations
202Os
N=126
neutron number
~0.3%
atomic number
Z and A separations are essential
for the lifetime measurements of rare channel products.
22
Kinematic condition for 202Os
198Pt
136Xe
9 MeV/A
202Os
~65°
12 mg/cm2
Large and wide
emission angle
~10°
Energy distribution
Yield (a.u.)
Yield (a.u.)
Angular distribution
Low energy,
wide energy spread
~< 0.5 MeV/A
Angle ( degree )
Energy ( MeV/A )
It would be difficult to separate and collect efficiently by using a spectrograph.
23
Total efficiency of gas catcher system
Total efficiency = estop × etrans × esurv × eLIS × eSPIG
Total efficiency
survival
=
transport
=
stopping
0.17
0.9
6.8% for 202Os
(T1/2 = 2.38 s
predicted by KUTY)
5.0% for 200W
(T1/2 = 423 ms
predicted by KUTY)
half-life (sec)
KUTY : T.Tachibana, M. Yamad, Proc. Inc. Conf. on exotic nuclei and atomic masses, Arles, 1995, p763.
24
Time schedule
FY
FY
FY
FY
FY
FY
Gas-catcher system will be installed
in this March
Off-line test of laser resonance ionization
is in progress
Mass separator will be installed
in the early months of the next FY
Construction, R&D Measurements (136Xe+198Pt)
25
R&D for laser resonance ionization
Pump lasers : Excimer laser (Lambda Physik LPX240i) 100 mJ/pulse @ 200 Hz
Frequency tunable dye lasers (Lambda Physik FL3002 l2 : 10mJ/p, ScanMate2E+SHG l1 : 1mJ/p)
Channeltron for secondary
electron detection
Ions
FL3002
for VIS.
ScanMate2E
for UV, l1
FL3002
for VIS., l2
Electrode
~ 350 V/cm
Control PC
Filament : Ni, Ir…
Ionization chamber
( Vacuum )
Wave meter
Excimer
lasers
Photo detector
for timing tuning
Power meter
26
Rhenium ionization ( Z = 75, A=185, 187 )
800
700
1st step 417.253nm fix
2nd step scan
AIS
600
Ionization energy :
Ei = 63181.6 cm-1 ( = 7.83 eV)
融点：3459K
AIS
Ei
l2 < 655.78 nmで
IPを越える
6F0 (J=7/2)
Ex = 47932.55cm-1
l1 = 208.6265 nm
(SHG)
 l0 = 417.2530 nm
(fundamental)
6S
(J=5/2)
AIS
649.84 nm
652.22nm
654.64nm
500
400
300
Ionization
limit
200
100
0
646
648
650
500
652
654
l2 (nm)
656
658
660
1st step scan
w/o 2nd step
1st step
208.6265nm
400
300
200
100
417.20
417.22
417.24
417.26
l0 (nm)
417.28
417.30
27
Power dependence
1st stepのパワー依存性測定
2nd stepのパワー依存性測定
2nd step 2.2mJ/p(飽和している)
1st step 417.253nm, 28.4mJ/p
(飽和している)
l1 power (mJ/p@f10mm)
l2 power (mJ/p@f10mm)
2nd step
2nd step
2nd step
l1 power (1014 photon/cm2 pulse)
100mJ/p(<1mJ/p),
2nd step
l2 power (1016 photon/cm2 pulse)
2 mJ/p(<10mJ/p)
l1 = 208.6265nm, l2 = 652.218nmでイオン化するのが効率良い。
ガスセル入り口(f10mm)で必要なパワーは、
1st : 100mJ/p(<1mJ/p), 2nd : 2 mJ/p(<10mJ/p)
28
Iridium ionization ( Z = 77, A=191, 193 )
1st step 417.900nm fix
2nd step scan
1000
Ionization energy :
Ei = 72323.9 cm-1 ( = 8.97eV)
融点： 2739K
AIS
Ei
l2 < 408.74 nmで
IPを越える
800
AIS
600
AIS
400
Ionization
limit
200
0
408
408.5
10 (J=11/2)
Ex = 47858.45cm-1
l1 = 208.950 nm
(SHG)
 l0 = 417.900 nm
(fundamental)
4F
(J=9/2)
408.186nm
408.217nm
408.266nm
408.434nm
409.520nm
400
409
l2 (nm)
409.5
410
1st step scan
w/o 2nd step
1st step
208.950 nm
300
200
100
0
417.80
417.84
417.88
417.92
l0 (nm)
417.96 29
Power dependence
1st
2nd stepのパワー依存性測定
stepのパワー依存性測定
l2 power (mJ/p@f10mm)
l1 power (mJ/p@f10mm)
40
0
120
80
160
800
2nd step
408.434nm
(1.15mJ/p)
600
0
1
2
3
4
5
6
7
8
2nd step
1200 408.217nm
st
1000 (1 17mJ/p)
9 10
2nd step
408.434nm
(1st 17mJ/p)
800
600
400
0
0.4
0.8
1.2
1.6
200
0
2.0
l1 power (1014 photon/cm2 pulse)
100mJ/p(<1mJ/p),
2nd step
408.217nm
(1st 3mJ/p)
400
2nd step
408.217nm
(1.18mJ/p)
200
0
1400
0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
l2 power (1016 photon/cm2 pulse)
3 mJ/p(<10mJ/p)
1st : 208.950nm, 2nd : 408.434nmでイオン化するのが効率良い。
ガスセル入り口(f10mm)で必要なパワーは、
1st : 100mJ/p(<1mJ/p), 2nd : 3mJ/p(<10mJ/p)
今後、W (Z=74), Ta (Z=73), Os (Z=76)等の共鳴イオン化様式を探索予定
30
E2, E3実験室におけるKISS設置予定（上から見た図）
絶縁トランス(<100kV)
高電圧プラットホーム(~60kV)
t50mm絶縁シート
高電圧防護柵(予定)
一次ビームライン整備
ゲートバルブ
2011年度内希望
一次ビームモニターチャンバー
絶縁ダクト
Ar gas セル50kPa@高電圧
EQダブレット
Dipole Mag.
E2
E3
レーザー光
J3 → E2
2010年度3月設置予定
高電圧プラットホーム
Ar gas セルハウジング真空槽
Ar gas セル
引出しチャンバー
2011年度設置予定
高電圧防護柵
引出しチャンバーより下流ライン
J3にレーザ装置(E2の地下)
差動排気用真空槽 40Pa@高電圧
引出しチャンバー
MQダブレット
測定用チャンバー
31