Transcript Photonuclear reactions in astrophysics 1 Nucleosynthesis of heavy elements

Photonuclear reactions in astrophysics
中日NP2006: 上海(Shanghai), May 16 - 20, 2006
H. Utsunomiya (Konan Univ)
1 Nucleosynthesis of heavy elements
2 Photonuclear reactions in stars
3 Laboratory studies: 12 nuclei
D, Be-9, Se-80, Zr-90,94, Pd-108, La-139, Pr-141,
Ta-181,W-186, Re-187, Os-188
4 Conclusions
Collaborators
1) <Konan> S. Goko, A. Makinaga, H. Akimune, T. Kaihori, S. Hohara
2) <AIST> H. Toyokawa, K. Kudo, A. Uritani, H. Harano, T. Matsumoto
3) <Kyoto> H. Ohgaki
4) <Numazu> K. Sumiyoshi
5) <NAO> T. Kajino
6) <Darmstadt> P. Mohr
7) <SPring-8> H. Yonehara, K. Soutome, N. Kumagai, H. Ohkuma,
8) <Texas A&M> Y.W. Lui
9) <Univ. Libre de Bruxelles> M. Arnould, S. Goriely, M. Rayet
10) <Orsay> E. Khan
11) <JAEA> H. Harada, F.Kitatani, K.Y. Hara, T. Hayakawa, H. Shizuma
Solar abundances of heavy elements
H: 71% (mass %)
He: 27%
Metal: 2%
3W (what, where, when) &
1H (how)
10 2
s
10 1
10 0
r
10 -1
10 -2
p
10 -3
138
10 -4
Who? (Nature or God)
10
-5
10
-6
La
180
W
180
80
100
120
140
A
160
180
Ta
200
Nucleosynthesis of heavy elements
p-nuclei
 35 neutron-deficient nuclei with small
solar abundances:74Se - 196Hg
GSI Darmstadt
Stellar Model of the p-process
Arnould (1976)
Woosley & Haward (1978)
Rayet et al. (1995)
Rauscher et al. (2002)
Arnould & Goriely (2003)
 2000 nuclei，20000 reactions :
Photodisintegration: (g,n)(g,p)(g,a)
Capture reactions: (n,g)(p,g)(a,g)
Weak transformation: b-decays, e±-captures,
(anti)neutrino-captures
 Temperature：(1.5 ～3.5) x 109 K
 Promising sites:
O/Ne-rich layer of massive stars during their explosions
as Type II(core collapse)-supernovae or in pre-supernova
phase
Type Ia-supernovae
Photoreaction rate for nuclei in the
ground state
g j 

 c ng (E,T )g
j
(E)dE
j= n, p, a
0
1
E2
ng (E,T )dE 2
dE
3
 ( c) exp( E / kT )1
1
Planck distribution
neutron channel

Gamow peak
GDR cross section
Planck distribution
Stellar Photoreaction Rate
g n
*
m
(2J m 1) m g n (T )exp( m / kT )
m
m
(2J
1)exp(

/ kT )
m
(nucleus in state m)
Z, A-1
Z, A
Nuclei are thermalized
under stellar conditions
Hauser-Feshbach model
m

m

T
(J
)T
(J
)
1
g
n
m
2
 g n  j
(2J 1)

m
2(2J I 1) J 
Ttot (J  )

Tk (J ) Tk (J )   

 0
m

 max
 







T
(

,J
)

(

,J
,

)d

dJ
d

 J ,   k
(k  g ,n)
3 important nuclear parameters
g transmission coefficient
Particle (n,p,a) transmission coefficient
Level density
AIST
産総研
National Institute of Advanced Industrial
Science and Technology
• Energy
Eg
Eg = 1 – 40 MeV
Inverse Compton Scattering
“photon accelerator”

L
Ee
Electron Beam
Laser
e
Eg 
L
e
g = Ee/mc2
1  b cos   L 1  cos L   )) E e
AIST (産総研)
Experimental Setup
TERAS:Tsukuba Electron Ring for Accelerating and storage
Laser System
mirror
depolarizer+expander
lens
mirror
TERAS
Laser
Nd:YVO4
Triple Ring Neutron Detector System
Triple ring detector: 20 3He counters (4 x 8 x 8 )
triple ring detectors
Monitor: NaI(Tl)
p process origin of 180Tam : tot at 109 K
Arnould, Goriely
s process origin of 180Tam : m at 108 K
Kaeppeler
Unknown
m : 179Ta(n,g)180Tam
180W
179Ta
181W
180m
182W
183W
181Ta
182Ta
180m
180g
181Hf
180g
176Hf
177Hf
178Hf
179Hf
s process
r process
180Ta
(odd-odd p-nucleus)
Nature’s rarest isotope
The one and only naturally-occurring isomer
H. Utsunomiya et al. 2003
Phys. Rev. C63, 018801
181Ta(g,n)180Ta
Extra E1-strength at low energy
Ta(g,n) 180Ta
(g,n) [mb]
181
100
10
1
IAEA [8]
Utsunomiya et al. (2002)
QRPA
Hybrid
Lorentzian
8
9
10
11
E [MeV]
12
13
Partial cross sections for the isomeric state
: m(E) for 181Ta(g,n)180Tam
Novel probe of Nuclear Level Density of
5ー
4ー
3ー
180Ta
9/2ー 7/2ー 5/2ー
2ー
s-wave neutron
180Tam
9−
1−
75 keV
> 1015 y
E1
8.152 h
180Ta
Selective multistep transitions
between high spin states
5ー → 6＋ → 7ー → 8＋ → 9ー
7/2+
181Ta
Total cross sections: tot(E) for
Direct neutron counting
181Ta
197Au
181Ta(g,n)180Ta
m(E)= tot (E) - gs(E)
Partial cross sections: gs(E) for
Photoactivation
181Ta(g,n)180Tags
gs(E):partial cross section for the ground state
181Ta(g,n)180Tags(EC)180Hf
Photoactivation
180Hf
KX rays
Partial cross sections for the isomeric state
: m(E) for 181Ta(g,n)180Tam
Combinatorial NLD: Hilaire et al. 2001: Goriely & Hilaire 2006
HFBCS pot. model: Demetriou & Goriely 2001
tot (E)
m(E)
S. Goko et al.
Phys. Rev. Lett.
May-2006 issue, in press
Partial neutron capture cross section
179Ta(n,g)180Tam
m = 90 ± 22 mb at 30 keV:
Statistical Model Calculation with the combinatorial NLD
Previously,
m = 44 mb
Conclusions
 Astrophysical photo-reactions and disintegrations
(APHRODITE) constitute an important research field in
connection with the origin of heavy elements by probing
・E1 g strength function above/below neutron thresholds
・nuclear level density
The following three research activities are important:
(1) Photonuclear reaction experiments (g,n) (g,p) (g,a) (g,g’)
(2) Nuclear theory and astrophysical modeling
(3) New photon sources in the MeV region
10 tesla Super-Conducting Wiggler
Yonehara, Soutome & Kumagai
SPring-8
10T- SCW synchrotron radiation
Black-body radiation
at billions of Kelvin
Determination of
Laboratory reaction
rates for (g,n), (g,p),
and (g,a) reactions
Utsunomiya et al., 2005
NIMA538, 225