Experimental project for production of neutron-rich nuclei by multinucleon transfer reaction (KISS project) DCEN2011 Oct. 24, 201 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. Matsuo K.U. Leuven P. Van Duppen, Y. Kudryavsev, M. Huyse 1
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Experimental project for production of neutron-rich nuclei by multinucleon transfer reaction (KISS project) DCEN2011 Oct. 24, 2011 Y.X. Watanabe (KEK)
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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)
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
• 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