Experimental project for production of neutron-rich nuclei by multinucleon

transfer reaction (KISS project)

DCEN2011 Oct. 24, 2011

Y.X. Watanabe (KEK) for KISS collaboration

Collaborators

KEK H. Miyatake, S.C. Jeong, H. Ishiyama, N. Imai, Y. Hirayama, K. Niki, M. Okada, M. Oyaizu, Y.X. Watanabe

RIKEN M. Wada, T. Sonoda, Y. Ito, Y. MatsuoK.U. Leuven P. Van Duppen, Y. Kudryavsev, M. Huyse

1

A half of elements heavier than Fe is considered to be produced by rapid neutron capture process (r-process)

N=126

3rd

peak

(A~1

95)

A

Obser

ved

solar

r-ab

unda

nce

distr

ibuti

on

H. Grawe et al., Rept. Prog. Phys. 70 (2007)1525.

Better understanding of r-process scenario

• Actual r-process path

• Astrophysical Nn-T condition

• Duration time passing through waiting point

• Actinide element production rate

Nuclear characteristics (T1/2, Sn, …)

N = 126 (Waiting point)

Lifetime measurements around N=126 → Astrophysical environments of r-process

Astrophysical nucleosysnthesis by r-process

Fe

2nd p

eak

N = 82

2

N

Z

r-process

5×108 years ≤ T1/2

30 days ≤ T1/2 < 5×108 years

10 minutes ≤ T1/2 < 30 days

T1/2 < 10 minutes

unknown

196Hg

196Pt 198Pt

209Bi

203Tl 205Tl 207Tl

198Hg 199Hg 200Hg 201Hg 202Hg 206Hg

197Au 205Au

204Pt

203Ir

201Re

200W

208Pb

204Hg

202Os

193Ir

192Os

195Pt194Pt

125124123122121120119118117116neutron number

126

MNT

136Xe + 198Pt

206Pb204Pb 207Pb

• 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

Lifetime measurements around N=126 nuclei

3

atom

ic n

umbe

r

74

75

76

77

78

79

80

81

83

82

136Xe beam

Ar gasGas catcher system - Target (iso-pure 198Pt) - Gas cell (Ar gas) - Laser resonance ionization - SPIG (SextuPole Ion Guide)

Lase

rs

Extraction chamber - Electric lens - Monitors

ISOL (Ion Separator On-Line) - Electric-Q doublet - Magnetic dipole - Magnetic-Q doublet

Focusing chamber - Electric-Q triplet - Electric deflector - Slit - Monitors

Detection system - 3 detection stations - Tape-transport system - Multi-layered plastic scintillators - Ge detectors - Lifetime measurements - -decay spectroscopy

KEK Isotope Separation System (KISS) @ RIKEN

4

from RIKEN ring cyclotron

MNT reactions

Points of project

Aimed reaction channels are very rare.

• Estimation of

are very important subjects from theoretical and experimental point of view

• A lot of contaminants → Isotopic separation (Z) ISOL → Mass separation (A)

• Small production yields as well as short lives

Efficient collectionFast extraction

→ Efficient measurements

Gas catcher system

Low background detection system

Laser resonance ionization

Absolute cross sectionsIsotopic distribution

gas flow

++

Gas cell filled with0.5 atm. Ar gas

198Pt

Ar g

as

Laser resonanceionization(Z selection)

Ion source chamber 37 PaScrew Pump 175 L/s

Extraction chamber 105 PaTMP 1500 L/s

Separations of Z and A are achieved by laser resonance ionization and ISOL, respectively.

VRF

VSPIG

V0 60 kV �

2nd chamber 6×102 PaTMP 1600 L/s

136Xe9 MeV/A

P. Van Duppen, Nucl. Instrum. Meth. B126 (1997) 66.Yu. Kudryavtsev et al., Nucl. Instrum. Meth. B267 (2009) 2908.

SPIG (SextuPole Ion Guide)

Gas catcher system— Laser resonance ionization + ISOL —

6

�

+ + ISOL(A separation)

Beam diameter : � 1 mm emittance : 10 � mm · mrad

10 cm

3 cm

Cross-sectional view of stopping distribution (202Os fragments)

transport time ( msec )extr

acte

d yi

elds

(a.u

.)

Mean transport time = 253 msTransport efficiency : tra = 56%

Calculated transport time profile

0 200 400 600 800 1000 1200 14000

40

80

120

160

136Xebeam

198Pt target

Top view of gas cell

laminar flow

ion collectorelectrode

laser

Argas

0 1 2 3 4 5 cm

exit hole(1 mm)

Simulation by hydrodynamic calculations

Ar g

as0.

5 at

m.

Gas cell design- Efficient collection and rapid extraction -

7

(mm)

(mm

)

Stopping efficiency :stop = 87 % half-life (sec)

surv

ival

pro

babi

lity

Survival probability : sur = 72% (T1/2 = 500 msec)

0.2

0.4

0.6

0.8

1.0

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Evaluated survival probabilitiesof radioactive nuclei

Frequency tunabledye lasers

1

2

excimer laserLPX240i

Gas cell

dye laserScanMate2E

dye laserFL3002

excimer laserLPX240i

Laser resonance ionization- Element selection -

1

2

g.s.

Ex

ionizationionization

EI

autoionizing state(AIS)

atomic energy levels(extracted fragment)

laser

laser

Intermediate state

Schematic diagram of laser system setup

1 and 2 tuning for the most efficient ionization-schemes of radioactive isotopes

1 : 210 – 450 nm 2 : 350 – 660 nm

Combination of two laser wavelengths for ionization is intrinsic to each element

Z selectionStable isotopes (Z = 69–78)

3 detection stations

1st 2nd 3rd

Beam

Switching box

200W : production rate = 0.11 pps

~1 × 104 particles/day

-decay detection rate: ~160 counts/day

Lifetime with 10% error

Beam

Tape transport system

Detection system

Plastic scintillatorsfor rays ( = 80%)

Ge detectors for X rays(X = 60% for 70 keV X-ray)

( = 20% for 500 keV -ray)

Ge detectors for rays

9

from

ISOL

Detection station

beamon

beamoff

beamon

beamoff

beamon

beamoff

beamon

beamoff

beamon

beamoff

beamon

beamoff

switch

switch switch

1ststation

2ndstation

3rdstation

Ton Toff 0.5 s tape movement(50cm)

Toff = T1/2 × 3

Ton = T1/2 × 2

Beam-on/off time-sequence

Os

Re

W

Ta

Hf

Lu

Yb

Ir

Pt

Au

120 121 122 123 124 125 126

1 s

10 ms

0.1 s

1 min

1 h

1 day

N

T1/2 (predicted by KUTY)

wai

ting

nucl

ei

200W

Limitation of lifetime measurements

Multinucleon transfer (MNT) reaction

L. Corradi et al., Physical Review C59 (1999) 261.64Ni (6.1 MeV/A) +238U

6p 5p 4p 3p 2p 1p 0p

6n pick-up

• Rather large cross sections (~1 mb) for 6p-stripping channels

Experimental dataCalculations (GRAZING code)

A. Winther, Nuclear Physics A572 (1994) 191;A. Winther, Nuclear Physics A594 (1995) 203.

projectile-like fragments

10

• Up to 6n-pick-up channels for pure neutron transfer (0p)

Production distribution136Xe+198Pt @ 7 MeV/A

136Xe+208Pb @ 7.3 MeV/A

evaporation

evaporation

114 116 118 120 122 124 126Neutron number

82

Atom

ic n

umbe

r 80

78

76

74

114 116 118 120 122 124 126Neutron number

82

Atom

ic n

umbe

r 80

78

76

74

104 (mb)

103

102

10

1

101

102

103

104

104 (mb)

103

102

10

1

101

102

103

104

198Pt

208Pb

114 116 118 120 122 124 126Neutron number

82

Atom

ic n

umbe

r 80

78

76

74

104 (mb)

103

102

10

1

101

102

103

104

198Pt

114 116 118 120 122 124 126Neutron number

82

Atom

ic n

umbe

r 80

78

76

74

104 (mb)

103

102

10

1

101

102

103

104

208Pb

11

Excitation functions and yields

Excitation functions for production of N = 126 isotones

~ 0.1 mb for 202Os ~ 1 b for 200W

202Os

201Re

200W

199Ta

198Hf

197Lu

Expected yields for N = 126 isotones

5.0 pps for 202Os 0.1 ppsfor 200W

calculated by GRAZING code (http://personalpages.to.infn.it/~nanni/grazing)

12

5Elab (MeV/A)

6 7 8 9 10 11 12 13

101

cros

s se

ction

after

eva

pora

tion

(mb)

102

103

104

105

106

136Xe : 9 MeV/A, 2 pnA198Pt : 12 mg/cm2

202Os

200W

196

Mass (A)197 198 199 200 201 202 203 204

102

Yiel

d (p

ps)

101

102

103

104

105

10

1

Measurementlimit

MNT with RIB

116

Neutron number117 118 119 120 121 122 123 124 125 126

81

Atom

ic n

umbe

r

79

77

74

717273

7576

78

80

8283 10

5

0

5

10

15

20

25

30

198Pt

116

Neutron number117 118 119 120 121 122 123 124 125 126

81

Atom

ic n

umbe

r

79

77

74

717273

7576

78

80

8283 10

5

0

5

10

15

20

25

30

198Pt

116

Neutron number117 118 119 120 121 122 123 124 125 126

81

Atom

ic n

umbe

r

79

77

74

717273

7576

78

80

8283 10

5

0

5

10

15

20

25

30

208Pb

116

Neutron number117 118 119 120 121 122 123 124 125 126

81

Atom

ic n

umbe

r79

77

74

717273

7576

78

80

8283 10

5

0

5

10

15

20

25

30

208Pb

198Pt target 208Pb target136Xe beam

144Xe beam

144Xe + 198Pt : Cross sections

136Xe+198Pt @ 7 MeV/A 144Xe+198Pt @ 7.2 MeV/A

14

82

Atom

ic n

umbe

r 80

78

76

74

72

104

(mb)

103

102

10

1

101

102

103

104118 120 122 124 126 128 130

Neutron number

82

Atom

ic n

umbe

r 80

78

76

74

72

104

(mb)

103

102

10

1

101

102

103

104118 120 122 124 126 128 130

Neutron number

198Pt 198Pt

140, 144Xe + 198Pt : Yields

15

= 0.01

(Proton-induced fission of U at the total fission rates of 1014 Hz)

198Hf, one of the waiting nuclei, would be accessed by using RIB 140Xe

Expected yields of N=126 isotones(E~9 MeV/A, optimized target thickness)

136 Xe+198 Pt

140 Xe+198 Pt

fragmentation

(238 U+Be)

144Xe+198Pt

194

Mass (A)

196 198 200 202 204106

104

102

1

102

104

Yiel

d (p

ps) waiting nuclei

1011

Beam

inte

nsity

(pps

)

109

108

107

106

105

104

103

136Mass (A)

138 140 142 144 146

Expected beam intensities of Xe isotopes

144Xe

140Xe

(W)(Hf)(Yb)(Er) (Os) (Pt)

Measurementlimit

16

+ particle evaporation

( L. Corradi et al., Phys. Rev. C66 (2002), 024606. )58Ni + 208Pb

Independentsingle-nucleon transfermodes

+ one pair transfer mode

Isotopic distributions of PLFs (proton stripping channels)0p1p2p3p4p5p6pcalculation

50 60 50 60 50 60 50 60 50 60 50 60 50 60Mass number

50 60 50 60 50 60 50 60 50 60 50 60 50 60Mass number

50 60 50 60 50 60 50 60 50 60 50 60 50 60Mass number

For better description Absolute cross sections ← Pair transfer

Understanding of MNT reactions

Isotopic distributions ← Energy dissipation (Evaporation)

Experiment with VAMOS at GANIL

17

PLF Trajectory Path length, Angles, B Velocity Total kinetic energy Mass, Atomic number, Charge

136Xe(8 MeV/A)

~ grazing angle

198Pt(1.3 mg/cm2)

• MWPC• Drift Chambers 2• Ionization Chamber• Silicon Wall

VAMOS

EXOGAM

12 (or 11) cloversSuppression shield configuration B with full Compton suppression

TLF-rays ~500 keV total photo-peak efficiency ~10%

MW

PC

DC2DC1

ICSSD

34°

18

PLF (mb)

136Xe

Calculated by GRZAING code ( A. Winther, program GRAZING, http://personalpages.to.infn.it/~nanni/grazing ).

TLF (mb)

198Pt

-transitions are known (Z=75~77)

Cross sections to produce PLFs and TLFs by MNT reactions of 136Xe+198Pt

• PLF : fragments are detected by VAMOS ( > 1 b ↔ 4-proton pick-up channels)• TLF : -rays are detected by EXOGAM (> 10 b ↔ 3-proton pick-up channels) Unknown -decay scheme Systematic tendency of gamma transitions over isotopic chains New isotope 202Os

4p pick-up

3p pick-up

Cross section measurements for 136Xe + 198Pt

• Investigation of astrophysical environment of r-processLifetime measurements for nuclei around N=126

• Nuclear production by MNT reactions of 136Xe+198PtRare events, Large contaminants

• KEK Isotope Separation System (KISS) at RIKENGas catcher system : Efficient collection, Fast ExtractionLaser resonance ionization + ISOL : Z & A separationLow-background detection system : 10% error for 200W

• Nuclear production by MNT reactions with neutron-rich RIB198Hf, 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

Summary

20

Q-value

21

22

Isobaric distribution (A=202)

(m

b)

~0.3%

202Os

atomic number

~99.7% contaminations

198Pt

(mb)136Xe + 198Pt

neutron number

atom

ic n

umbe

r

Z and A separations are essential for the lifetime measurements of rare channel products.

202Os

Contaminations

isobar

N=126

23

202Os

~65°136Xe 9 MeV/A

198Pt

12 mg/cm2

Angular distribution

~10°

Angle ( degree )

Yiel

d (a

.u.)

Energy distribution

Energy ( MeV/A )

Yiel

d (a

.u.)Large and wide

emission angleLow energy,wide energy spread

Kinematic condition for 202Os

< 0.5 MeV/A~

It would be difficult to separate and collect efficiently by using a spectrograph.

24

5.0% for 200W (T1/2 = 423 ms predicted by KUTY)

6.8% for 202Os(T1/2 = 2.38 s predicted by KUTY)

Total efficiency of gas catcher system

Total efficiency = stop × trans × surv × LIS × SPIG =

0.17=

0.9stopping transport survival

half-life (sec)KUTY : T.Tachibana, M. Yamad, Proc. Inc. Conf. on exotic nuclei and atomic masses, Arles, 1995, p763.

Tota

l effi

cien

cy

25

FY FY FY FY FY FY

Time schedule

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

Measurements (136Xe+198Pt)Construction, R&D

Excimerlasers

FL3002for VIS., 2

ScanMate2Efor UV, 1

FL3002for VIS.

Channeltron for secondaryelectron detection

Filament : Ni, Ir…Electrode~ 350 V/cm

Ions

Pump lasers : Excimer laser (Lambda Physik LPX240i) 100 mJ/pulse @ 200 HzFrequency tunable dye lasers (Lambda Physik FL3002 2 : 10mJ/p, ScanMate2E+SHG 1 : 1mJ/p)

R&D for laser resonance ionization

Wave meter

Control PC

Photo detectorfor timing tuning

Power meter

Ionization chamber( Vacuum )

2

0

1

26

Rhenium ionization ( Z = 75, A=185, 187 )

1st step scanw/o 2nd step

0 (nm)

1st step 417.253nm fix2nd step scan

649.84 nm652.22nm654.64nm

2 (nm)

Ionization limit

6S (J=5/2)

6F0 (J=7/2)

Ex = 47932.55cm1 = 208.6265 nm (SHG) 0 = 417.2530 nm (fundamental)

2 < 655.78 nm でIP を越える

Ionization energy : Ei = 63181.6 cm-1 ( = 7.83 eV) 融点： 3459K

417.20 417.22 417.24 417.26 417.28 417.30100

200

300

400

5001st step 208.6265nm

AISEi

200

300

400

500

600

700

800

100

0646 648 650 652 654 656 658 660

AIS

AIS

27

Power dependence

1st step のパワー依存性測定2nd step 2.2mJ/p( 飽和している )

1 = 208.6265nm, 2 = 652.218nm でイオン化するのが効率良い。ガスセル入り口 (mm) で必要なパワーは、 1st : 100J/p(<1mJ/p), 2nd : 2 mJ/p(<10mJ/p)

1 power (J/p@mm)

1 power (photon/cm2 pulse)

2nd step

2nd step

100J/p(<1mJ/p),

2 power (photon/cm2 pulse)

2 power (mJ/p@mm)

2nd step のパワー依存性測定1st step 417.253nm, 28.4J/p ( 飽和している )

2nd step

2nd step

2 mJ/p(<10mJ/p)

28

Iridium ionization ( Z = 77, A=191, 193 )

4F (J=9/2)

10 (J=11/2)

Ex = 47858.45cm1 = 208.950 nm (SHG) 0 = 417.900 nm (fundamental)

2 < 408.74 nm でIP を越える

Ionization energy : Ei = 72323.9 cm1 ( = 8.97eV)融点： 2739K

AISEi

1st step scanw/o 2nd step

417.80 417.84 417.88 417.92 417.960 (nm)

300

200

100

0

400 1st step208.950 nm

2 (nm)408 408.5 409 409.5 410

0

200

400

600

800

1000

AIS

AIS

1st step 417.900nm fix2nd step scan

Ionizationlimit

408.186nm408.217nm408.266nm408.434nm409.520nm

29

Power dependence

0 40 80 120 160

0

200

400

600

800

0 0.4 0.8 1.2 1.6 2.0

1 power (J/p@10mm)

1 power (photon/cm2 pulse)

1st step のパワー依存性測定 2nd step のパワー依存性測定

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 (mm) で必要なパワーは、 1st : 100J/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

2nd step408.434nm(1.15mJ/p)

2nd step408.217nm(1.18mJ/p)

0

200

400

600

800

1000

1200

1400

0 0.4 0.8 1.2 1.6 2.0 2.4 2.8

2 power (photon/cm2 pulse)

0 1 2 3 4 5 6 7 8 9 10

2 power (mJ/p@mm)

2nd step408.434nm(1st 17J/p)

2nd step408.217nm(1st 3J/p)

2nd step408.217nm(1st 17J/p)

100J/p(<1mJ/p), 3 mJ/p(<10mJ/p)

30

5808

E2

E3

高電圧プラットホーム (~60kV)t50mm 絶縁シート

差動排気用真空槽 40Pa@ 高電圧

高電圧防護柵 ( 予定 )

MQ ダブレット

引出しチャンバー

Dipole Mag.

E2, E3 実験室における KISS 設置予定（上から見た図）

EQ ダブレット

一次ビームライン整備2011 年度内希望

ゲートバルブ

一次ビームモニターチャンバー

絶縁ダクト

絶縁トランス (<100kV)

Ar gas セル 50kPa@ 高電圧

測定用チャンバー

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 )

レーザー光J3 　→ E2

31