Determination of radiative neutron capture cross sections for unstable nuclei by Coulomb dissociation
H. Utsunomiya (Konan University)
Outline
1. Methodology of the SF method
2. Applications with real photons
3. Applications with virtual photons
RIKEN Seminar Nov. 1, 2011
Collaborators
H. Utsunomiyaa) , H. Akimunea) , T. Yamagataa) , H. Toyokawac) , H. Haradad), F. Kitatanid) ,Y. -W. Luie) ,S. Gorielyb) I. Daoutidisb) , D. P. Arteagaf) , S. Hilaireg) , and A. J. Koningh)
a) Department of Physics, Konan University, Japanb) Institut d’Astronomie et d’Astrophysique, ULB, Belgiumc) National Institute of Advanced Industrial Science and Technology, Japan d) Japan Atomic Energy Agency, Tokai, Naka-gun, Ibaraki 319-1195, Japane) Cyclotron Institute, Texas A&M University, USA f) Institut de Physique Nucléaire, Université Paris-Sud, France g) CEA,DAM, DIF, Arpajon, Franceh) Nuclear Research and Consultancy Group, The Netherlands
Radiative neutron capture cross sectionsfor unstable nuclei in nuclear astrophysics
Direct measurements at CERN n-TOF, LANSCE-DANCE, Frankfurt-FRANZ and J-Parc ANNRI facilities
can target some of unstable nuclei along the valley of -stability if samples can be prepared. ---> s-process
Indirect experimental method is called in for unstable nuclei along the valley of -stability ---> s-process neutron-rich region ---> r-process
surrogate reaction technique ANY OTHER?
follows the statistical model of the radiative neuron capture in the formation of a compound nucleus and its decay by using experimentally-constrained SF.
-ray strength function methodH. Utsunomiya et al., PRC80 (2009)
n + AX
A+1X
E, J,
AX(n,)A+1XRadiative neutron capture
continuum
SF NLD
decay process
n(E) kn
2 gJ
T(E,J, ) Tn (E,J, )
TtotJ ,
T(E,J,) TX ()
,X , TX () (E )d
X ,
Total transmission coefficient
€
TXλ (εγ ) = 2π ΓXλ /D
fXλ (εγ ) ↓= εγ−(2λ +1)
ΓXλ (εγ )
D
-ray strength function nuclear level density
(E )X=E, M=1, 2, …
SF method
neutron resonance spacinglow-lying levelssource of uncertainty
Hauser-Feshbach model cross section for AX(n,)A+1XHauser-Feshbach model cross section for AX(n,)A+1X
After integrating over J and π
-ray strength function: nuclear statistical quantity interconnecting (n,) and (,n) cross sections
in the HF model calculation
n+AX
A+1X
E, J, AX(n,)A+1X
€
fXλ (ε γ ) ↓= ε γ−(2λ +1)
ΓXλ (ε γ )
D
A+1X(,n)AX
fX ()
21
(hc)2
Xabs()
2 1
Photoneutron emissionRadiative neutron capture
fX () fX () Brink Hypothesis
Xn () X
abs() Tn
Tn T
continuum
€
fXλ (ε γ )
Sn
Sn
SnGDR
PDR, M1
Structure of -ray strength function
Primary strength E1 strength in the low- energy tail of GDR
Extra strengths
6 – 10 MeV
SnGDR
PDR, M1
(,n)(,’)
Particle- coin.
CDOslo method
R. Schwengner R. Schwengner
A. Zilges A. Zilges
M. Guttormsen M. Guttormsen
(p,p’)A. TamiiP. von Neumann-CoselA. TamiiP. von Neumann-Cosel
A. Tonchev A. Tonchev
Sn
(,n) GDR
Methodology of SF method
STEP 1
Measurements of (,n) c.s. near Sn
A-1A-1 AA
(,n) SFSTEP 1
Sn
Methodology of SF method
STEP 2
Normalization of SF
Extrapolation of SF by models
Sn
(,n) GDR
A-1A-1 AA
(,n) SFSTEP 1
JUSTIFICATION BY REPRODUCING KNOWN (n,) C.S.
Methodology of SF method
STEP 2
known (n,)
SnSn
(,n) GDR
A-1A-1 AA
(,n) SFSTEP 1
neutron capture byunstable nucleus
Methodology of SF method
STEP 3
(n,) to be deduced
A+1A+1 A+2A+2
(,n)
STEP 3
A+1X(n,)A+2X
known (n,)
A-1A-1 AA
(,n)
STEP 1STEP 2
Extrapolation is made in the same way as for stable isotopes.
(,n) GDR
Sn
STEP 1STEP 2
66Sn 116 117 118 119 12012127 h 122
123129 d 124
105 106 1076.5 106 y 108Pd
90 91 92 931.53 106 y 94
9564 d 96Zr
77 78 792.95 103 y 80Se 76 75
120 d
89 3.27 d
104
66115
Applications LLFP (long lived fission products) nuclear waste
Astrophysical significancePresent (,n) measurementsExisting (n,) data
7
3
5
4
H.U. et al., PRC82 (2010)
H. Utsunomiya et al., PRC80 (2009)
H.U. et al., PRL100(2008) PRC81 (2010)
To be published
(n,) c.s. to be deduced
EE
L
L L e
1 1cos cos
e
e
E
L
Ee
•• EnergyEnergy
Laser Electron Beam
Inverse Compton Scattering
= Ee/mc2
“photon accelerator”
Laser Compton scattering -ray beam
=1064, 532 nm
AIST (National Institute of Advanced Industrial Science and Technology)
Detector System
Triple-ring neutron detector20 3He counters (4 x 8 x 8 ) embedded in polyethylene
90 91 92 931.53 106 y 94
9564 d 96Zr 89
3.27 d
ApplicationsLLFP (long lived fission products) nuclear waste
Astrophysical significance
Present (,n) measurements
5
Measurements of (,n) cross sections
Justification of SF with existing (n,) data
STEP 1
STEP 2 Investigation of SF that reproduces (,n) cross sections
Extrapolation of SF below Sn
STEP 3 Prediction of (n,) cross sections for 93Zr and 95Zr
STEP 1 – (,n) 断面積の中性子しきい値近傍での高精度測定
91Zr
92Zr
94Zr
96Zr
Application STEP 2 – Extrapolation of SF to the low-energy region
HFB+QRPA E1 strength supplemented with a giant M1 resonance in Lorentz shape
Eo ~ 9 MeV, ~ 2.5 MeV, o ~ 7 mb
~ 2% of TRK (Thomas-Reiche-Kuhn) sum rule of GDR
HFB+QRPA+ Giant M1
92Zr
Application STEP 2 – Justification of the adopted SF
TALYS code of the HF model
Application STEP 2 – Justification of the adopted SF
93Zr[T1/2=1.5×106 y]
Results for Zr isotopes
long-lived fission product nuclear waste
95Zr[T1/2=64 d] s-process branching
30-40% uncertainties
Comparison with the surrogate reaction techniqueForssèn et al., PRC75, 055807 (2007)
93Zr(n,)94Zr
95Zr(n,)96Zr
1. The surrogate reaction technique gives larger cross sections by a factor of ~ 3 than the SF method.
The surrogate reaction technique gives similar cross sections to those given by the SF method provided that a choice is made of the Lorentian type of SF.
Zr isotopes
66Sn 116 117 118 119 12012127 h 122
123129 d 12466115
Applications
7
STEP 1 Measurement of (,n) cross sections
Sn isotopes
H. Utsunomiya et al., PRC80 (2009)
HFB+QRPA E1 strength supplemented with a pygmy E1 resonance in Gaussian shape
Eo ~ 8.5 MeV, ~ 2.0 MeV, o ~ 7 mb
~ 1% of TRK sum rule of GDR
STEP 2 – Extrapolation of SF to the low-energy region
HFB+QRPA+ PDR
SF for Sn isotopes
Toft et al., PRC 81 (2010)PRC 83 (2011)
Comparison with the Oslo method
STEP 2 – Justification of the extrapolated SF
STEP 3 – Statistical model calculations of (n,) cross sections for radioactive nuclei
121Sn[T1/2=27 h]
123Sn[T1/2=129 d]
Uncertainties: 30-40%
Uncertainties: a factor of 3
105 106 1076.5 106 y 108Pd 104
ApplicationsLLFP (long lived fission products) nuclear waste
Astrophysical significance
3
STEP 1 Measurement of (,n) cross section
Pd isotopes
SF for 108Pd STEP 2 – Extrapolation of SF
RMF + QRPA D. P. Arteaga and P. Ring, Phys. Rev. C77, 034317 (2008)
Sn
STEP 2 – Justification of the extrapolated SF
D. P. Arteaga and P. Ring, Phys. Rev. C77, 034317 (2008).
S. Goriely, Phys. Lett. B436, 10 (1998). Hybrid
Deformed RRPA
107Pd[T1/2=6.5×106 y] long-lived fission product nuclear waste
30-40% uncertainties stem from NLD
79Se(n,)80Se
77 78 792.95 103 y 80Se 76 75
120 d4
F. Kitatani (JAEA) a systematic measurement for stable Se isotopes ---> complete application of SF method To be published
A. Makinaga et al, PRC79 (2009)Large uncertainties has remained because of a lack of
justification in STEP 2.
s-process nucleosynthesis and stellar models
€
A NA
€
A€
A = σv /vT
€
vT =2kT
μn
⎛
⎝ ⎜
⎞
⎠ ⎟
1/ 2
Main componentMain componentWeak componentWeak component
Zr 〜 BiFe 〜 Zr
MainMainWeakWeak
Zr
AGB stars ( 1 ≤M≤ 3 )He-shell burning
Massive stars ( 8 ≤ M )Core He burning
Carbon burning12C(12C,n)23MgkT ≈ 91 keVnn≈1011 cm-3
22Ne(,n)25Mg kT=26 keV, nn≤106 cm-3
13C(,n)16O kT=8 keV, nn≈107 cm-3
22Ne(,n)25Mg kT=23 keV, nn≤1011 cm-3
(E): E : 0.3 〜 300 keV
MACS
s-process branching nuclei
F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011)
s-only nuclei
The s-process branching is a good measure of the stellar neutron density and temperature.
151Sm(n,) @ n-TOF (CERN)
Sm2O3, 89.9% 151Sm, 206.4 mg
Normal applications of the SF method with real photons requires at least 2 neighboring stable isotopes.
s-process branching nuclei
F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011)
9 branching nuclei
63Ni79Se
81Kr, 85Kr95Zr
147Nd151Sm153Gd185W
(n,) to be deduced
A+1A+1 A+2A+2
(,n)
known (n,)
A-1A-1 AA
(,n)
s-process branching nuclei
F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011)
Some s-process branching nuclei have only one stable isotope.
stable133Cs159Tb165Ho169Tm181Ta203Tl
branching134,135Cs160Tb163Ho170,171Tm179Ta204Tl
8 branching nuclei
• Some s-process branching nuclei have 2 stable isotopes that are not neighboring to each other.
s-process branching nuclei
s-only nuclei3 branching nuclei
stable151,153Eu
branching152,154,155Eu
Coulomb dissociation experiments with SAMURAI at RIKEN-RIBF
s-process branching nuclei halflife(yr)
Coulomb dissociation (n,) data
134Cs,135Cs 2.0652, 2.3×
106 136Cs,135Cs,134Cs 133Cs
152Eu* 13.537 153Eu, 152Eu 151Eu
154Eu,155Eu 8.593, 4.753 156Eu,155Eu,154Eu 153Eu
160Tb 0.198 161Tb,160Tn 159Tb
163Ho 4570 164Ho,166Ho 165Ho
170Tm,171Tm 0.352, 1.921
172Tm,171Tm,170Tm 169Tm
179Ta 1.82 180Ta,182Ta 181Ta
204Tl 3.78 205Tl,204Tl 203Tl
11 branching nuclei 18 Coulomb dissociations
Ambitious application of the SF method to the r-process
The significance is controversial ! BUT this would be the first application to a very neutron-rich
nucleus.
A pioneering work is in progress.1) A systematic study of the SF for Sn isotopes116Sn ,…., 124Sn (7 stable) → → → 132Sn
132Sn(,n) data: GSI Coulomb dissociation data for 132Sn
131Sn(n,)132Sn cross sections in the r-process nucleosynthesis
New -ray Beam Line @ NewSUBARU
Summary
SF method: (n,) c.s. for unstable nuclei1. Nuclear Experiment: (,n) c.s. real photons for stable nuclei virtual photons for unstable nuclei (CD) 2. Nuclear Theory: models of SF models of NLD primary strength: low-energy E1 of GDR extra strengths: PDR, M1
3. Coulomb dissociation experiments with SAMURAI @ RIKEN-RIBF play a key role in the application of the SF method.
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