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Photoneutron cross section measurements with laser Compton‐scattering γ‐ray beams
Hiroaki Utsunomiya
(Konan University, CNS University of Tokyo)
Content1. γ‐ray sources
Positron annihilation in flight vs laser inverse Comptonscattering2.Photoneutron measurementsa. E1 (pygmy dipole resonance) and M1 cross sections b. Applications of the reciprocity theoremc. p‐process nucleosynthesis d. γ‐ray strength function for (n,g) c.s. for radioactive nuclei September 15 & 16, 2014Lomonosov Moscow State University (MSU)Skobeltsyn Institute of Nuclear Physics (SINP)Department of Electromagnetic Processes and Atomic Nuclei Interactions (DEPANI)
γ‐ray sources: Positron annihilation in flight
e‐beam
Converter (W, Au, Ta, Pt) e‐ → e+
e+
beam
Annihilation Target 9Be
γ-ray BeamEγ = Ke+ + 3/2(mc2)
Lawrence Livermore National Laboratory (USA)
e‐ bremsstrahlungPair production
Neutron detectorBF3 counters + paraffin
γ‐ray sources: Inverse Compton scattering
Compton scattering vs Inverse Compton scattering
Incident photon scattere
d photon
Recoiledelectron
2'
/)cos1(1 mchhh
φννν
−+=
4222'2 cmcphmch ++=+ νν
ψφνν coscos'
pc
hc
h+=
ψφν sinsin0'
pc
h−=
Lorentz factor
Compton scattering
Laser Compton scattering γ‐ray beam
γ= Ee/mc2 (Lorentz factor)� 2 x 103 Ee=1 GeV
Energy amEγ/εL=4γ2�1.6 x 107
εL� 1eVEγ � 16 MeV
7
SPring8
SACLA
NewSUBARU MeV γ
1 GeV e‐ Linac
8 GeV e‐ synchroton8 GeV e‐ linac
8 GeV e‐ storage ringLEPS, LEPS2GeV γ
NewSUBARU (Japan)
0.55 – 1.5 GeV storage ring
Eγ=0.5 – 76 MeVIγ = 106 – 107 s-1
(3 – 6 mm dia.)ΔE/E > 2%
LCS γ‐ray beams and response functions of a 3.5” x 4.0” LaBr3(Ce) detector
1.2% 1.4% 1.6%(FWHM)
Double collimation C1: 6mm, C2: 2mm
Sn GDR
PDR,M1
Extra strengths
γ‐ray strength function
6 – 12 MeV
(γ,γ’) (γ,γ’) (γ,n)(γ,n)
(p,p’)(p,p’)
Nuclear Resonance Fluorescence Photoneutron measurements
High‐resolution (p,p’) at 300 MeV
6 MeV for odd‐N nuclei ← Sn: → 12 MeV for even‐even nuclei
Spin and Parity Determination
N. Pietralla, at al. PRL 88 (2002) 012502; A. Tonchev, NIM B 241 (2005) 51474
Courtesy by A. Tonchev 138Ba
Resonances above Sn
207Pb(γ,n) 208Pb(γ,n)
C.D. Berman et al., PRL25, 1302 (1970)R.J. Baglan et al., PRC3, 2475 (1971)
Threshold Photoneutron TechniqueBremsstrahlung + n‐TOF
(p,p’) near 0o as Coulomb excitation of PDR
C. Iwamoto et al., Phys. Rev. Lett. 108, 262501 (2012)
90Zr(p,p’) at 295 MeVMultipole‐decomposition analysis of the proton angular distribution
PDR in Lorentzian shape
B(E1)↑�0.75 ± 0.08 e2 fm2 E=7‐11 MeVTRK sum rule 2.1±0.2%
EPRD = 9.15 ± 0.15 MeV, ΓPRD = 2.91 ± 0.64 MeV
EM1 = 9.53 ± 0.06 MeV, ΓΜ1 = 2.70 ± 0.17 MeV
E1 and M1 photoexcitations in 207Pb
207Pb
206PbE1
207Pb
206Pb0+
1/2‐
M1
1/2‐
0+1/2+ , 3/2+ 1/2‐ , 3/2‐
2,0= 1=
PDR in 207,208Pb T. Kondo et al., Phy. Rev. C 86, 014316 (2012)
Targets9587 mg, 98.5%, 208Pb 3482 mg, 99.1%, 207Pb
Five 3He proportional counters
Neutron DetectorHigh‐ and flat‐efficiency long counters
East & Walton, NIM 72 (1969)
Twelve neutron‐guiding holes
Linear polarizationP=93.4±0.7%
Angular distributions and Detection efficiencies of neutrons
W s(θ,φ) =1
4π
s‐wave neutrons
p‐wave neutrons
Wpolp (θ,φ) =
38π
[sin2 θ(1+ cos2φ)]
Wunpolp (θ,φ) =
38π
sin2 θ
ε 0
ε //1
ε⊥1
ε 1
ε //1
ε⊥1ε⊥
1
ε //1
ε 0
ε 0 ε 0
ε 0
ε1
ε1
ε1
ε1
Circularly‐polarized photons
PDR in 207,208Pb above neutron threshold
208Pb
207Pb
0+
1/2‐1‐ 1+
E1 M1
l = 0, 1
T. Kondo et al., Phy. Rev. C 86, 014316 (2012)9587 mg, 98.5%, 208Pb 3482 mg, 99.1%, 207Pb
W s(θ,φ) =1
4π
W polp (θ,φ) =
38π
[sin2 θ (1+ cos2φ)]
E1 cross sections for 208,207Pb
HFB+QRPA E1 strength plus pygmy E1 resonance in Lorentzian shape
Eo = 7.5 MeV, Γ = 0.4 MeV
TRK sum rule0.42% for 208Pb0.32% for 207Pb
σo ≈ 20 mb for 208Pbσo ≈ 15 mb for 207Pb
MeVEfmeEB
430.8515.7206.0982.0)1( 22
−=⋅±↑=
(p,p’) experiment
MeVEfmeEB
32.851.709.082.0)1( 22
−=⋅±↑=
208Pb
↑)1(EB
207Pb
MeVEfmeEB
32.802.717.088.0)1( 22
−=⋅±↑=
Present
Present results
B(E1) =0.82±0.09 e2 fm2 for 208Pb E=7.51 – 8.32 MeV
B(E1) =0.88±0.17 e2 fm2 for 207Pb E=7.02 – 8.11 MeV
(p,p’) I. Poltoratska et al., PRC 85, 041304(R) (2012)B(E1) =0.982±0.206 e2 fm2 for 208Pb E=7.515 – 8.430 MeV
E1
Comparisons
M1 cross sections for 208,207Pb
Eo = 8.06 MeV, Γ= 0.6 MeVσo = 3.6 mb
M1 strength in Lorentzian shape
208Pb
Eo ≈ 7.25 MeV, Γ ≈ 1 MeVσo ≈ 3.2 mb
207Pb
B(M1)=4.2 ± 2.3 μN2 E=7.51‐8.32 MeV
B(M1)=4.0 ± 1.9 μN2 E=7.02‐7.52 MeV
Present results
B(M1) =4.2±2.3 μΝ2 for 208Pb E=7.51 – 8.32 MeV
B(M1) =4.0±1.9 μΝ2 for 207Pb E=7.02 – 7.52 MeV
M1
207Pb+n R. Köhler et al., PRC 35, 1646 (1987)B(M1) =5.8 μΝ
2 for 208Pb E=7.37 – 8.0 MeV
Comparisons
Please formulate angular distributionsfor d‐ and f‐wave neutrons.
W (θ,φ) nXXX AAA +→→+ −∗→
1γ
W s(θ,φ) =1
4π
Wpolp (θ,φ) =
38π
[sin2 θ(1+ cos2φ)]
s‐wave
p‐wave
(d, f waves)
Nucleosynthesis of light nuclei
22 )12)(12()(
)12)(12()(
bbBaaA piIba
piIab
++→
=++
→ σσ
Reciprocity Theorem A + a → B + b + QB + b → A + a – Q Q value
Equivalency between (n, γ) and (γ,n)
a=n, b=γ cE
kp γγ == pn
2 =2μEn 2jb +1→2
A X
A −1X
n
γ
Neutron Channel
ExamplesBig Bang Nucleosynthesis: p(n,γ)D vs D(γ,n)p D
p
n
d t
3He 4He
7Li
7Be
1. n ⇔ p
2. p(n,γ)d
3. d(p,γ)3He
4. d(d,n)3He
5. d(d,p)t
6. t(d,n)4He
7. t(α,γ)7Li
8. 3He(n,p)t
9. 3He(d,p)4He
10. 3He(α,γ)7Be
11. 7Li(p,α)4He
12. 7Be(n,p)7Li
1
2
5
9
3 48
10
12
11
7
6
ExamplesBig Bang Nucleosynthesis: p(n,γ)D vs D(γ,n)p
K.Y. Hara et al., PRD 68, 072001 (2003)
D
Naσ
v (×
104 c
m3 /m
ole/
s)
E (MeV)
1
2
3
45
10
20
10-8 10-6 10-4 10-2 100 102
our dataprevious datafitJENDL
Our DataBirenbaum et al. (1985)Moreh et al. (1989)Bishop et al. (1950)
Nagai et al. (1997)Suzuki et al. (1995)
JENDL(σtotal)JENDL(σM1)JENDL(σE1)σ to
tal (
mb)
Eγ (MeV)
2 3 4 5 100.2
1.0
2.0
3.0
p(n,γ)D
D(γ,n)p
D(γ,n)p
ExamplesSupernova Nucleosynthesis α α⇄ 8Be(n,γ) 9Be vs 9Be(γ,n)8Be
9Be
Hot Proto-Neutron Star
νν
p,n
R Ѓ` 10 km
R Ѓ`50 km
R Ѓ`100 km
T Ѓ` 0.5 MeV α,n
T Ѓ` 0.2 MeV
α-process
Type II Supernova
n,seeds, α
r-proces
Neutrino-Driven Wind
α,n
ExamplesSupernova Nucleosynthesis α α⇄ 8Be(n,γ) 9Be vs 9Be(γ,n)8Be
9Be
0.0
0.5
1.0
1.5
2.0
1.6 1.7 1.8 1.9 2.0
0.0
0.5
1.0
1.5
2.0
1.5 2.0 2.5 3.0 3.5 4.0 4.5
σ(m
b)
Eγ(MeV)
H. Utsunomiya et al. PRC 63, 018801 (2001)K. Sumiyoshi et al. NPA709, 467 (2002)
ExamplesSupernova Nucleosynthesis α α⇄ 8Be(n,γ) 9Be vs 9Be(γ,n)8Be
9Be
C.W. Arnold et al. PRC 85, 044605 (2012) HIGS
A new measurement has been done by Konan University and CNS, University of Tokyo etc. at the NewSUBARU synchrotron radiation facility and data reduction is in progress.
�
�� (p,
�
γ)
(γ,n)
�
�
(p,γ) + β − decay
�
� (γ,n) + (γ, p)
(γ,n) + (γ,α) + β − decay
35 neutron‐deficient nuclei from Se(Z=34) to Hg(Z=80)
p‐nuclei
p‐process nucleosynthesis
P. Mohr et al., Phys. Lett. B 488 (2000) 127H. Utsunomiya et al., Nucl. Phys. A 777 (2006) 459
λγn (T) = cnγ (E,T)σγn (E)dE0
∞
∫
nγ (E,T )dE =
1π 2
1(hc)3
E2
exp(E / kT ) −1dE
Photoreaction rates for gs
Planck distribution
Planck distr.Photoneutron CS
Gamow peak
Stellar photoreaction rate
λγnμ (T) = cnγ (E,T)σγn
μ (E )dE0
∞
∫
Photoreaction rates for a state μ
σγn
μ (Eγ ) = πDγ2 1
2(2 j μ +1)(2J +1)
Tγμ (Eγ ,J
π )Tn (E,Jπ )Ttot (E,Jπ )J π
∑
Eγ
E, Jπ
A X
A −1XSn
μ, Eμ
E=Eγ+Eμ
Tγμ (E γ ,Jπ ) = 2πεγ
3 fγ (E γ ) ↑ for E1 transition
Eγ > Sn for gs
Eγ < Sn for excited states μ
Key quantity: γ‐ray strength function fγ (Εγ)
λγn* =
(2 j μ +1)λγnμ (T)exp(−ε μ /kT)
μ∑
(2 j μ +1)exp(−ε μ /kT)μ
∑
Stellar photoreaction rate
Only naturally occurring isomer 180Tam
• Odd-odd Nucleus (Z=73, N=107)• Neutron deficient nucleus (classified as one of p-nuclei)• Solar Abundance ; 2.48×10�6(the rarest)• Half Life > 1.2×1015y• Ex = 75keV• Jπ = 9-
180Tags
•Half Life = 8.152h
•Jπ = 1+
10 -6
10 -5
10 -4
10 -3
10 -2
10 -1
10 0
10 1
10 2
80 100 120 140 160 180 200A
180 Ta
180 W
r-process
p-process
s-process
138 La
Network of nucleosynthesis
178Hf
180W
180Tam 181Ta
182W 183W
180Hfm179Hfm
181W
179Ta 182Ta
181Hf
1.2×1015y
180Tags
179Hfgs 180Hfgs
8.2h
5.5h
1.8y
25d
XXnX AZ
AZ
AZ ′+
+−+ 1
11 )(),( βγPrimary s-process flow
p-process mTamequilibriuthermalTanTa 180180181 ) (),(γ
StableUnstable
r-process
Weak branching s-process mm TanTaHf 180179179 ),()( γβ
• p-process in the pre-supernova phase of massive stars or during their explosions as type-�supernovae
Temperature ; 1.8 � T[109K] � 3.0Peak photon energy ; 200[keV]
Nucleosynthesis of 180Tam
179Hfm(β)179Ta(n,γ)180Tam
• s-process in the Low-mass AGB starTemperature ; 2.9 � T[108K] � 3.3
(Zs. Nèmeth, F. Käppeler, G. Reffo; 1992)
Typical neutron energy ; 25[keV]
181Ta(γ,n)180Ta(thermal equilibrium) 180Tam
1
10
100
8 9 10 11 12 13
IAEA [8]Utsunomiya et al. (2002)QRPAHybridLorentzian
σ(γ,
n) [m
b]
E [MeV]
181Ta(γ,n)180Ta
H. Utsunomiya et al., Phys. Rev. C 67, 015807 (2003)
181Ta(γ,n)180Ta
Extra E1 γ-ray strength near Sn Pygmy Dipole ResonanceN. Paar, D. Vretenar, E. Khan, G. ColòRep. Prog. Phys. 70 691 (2007)
100
101
102
103
80 100 120 140 160 180 200
X /
Xso
lar
Mass Number
Se
Kr
Sr
Mo
Ru
Pd
Cd
In
SnTe
Xe
Ba
Ce
La
Sm
Gd
Dy
Er
Yb HfW
Ta
Os
Pt
Hg
Model calculation of the p‐process nucleosynthesis
H. Utsunomiya et al., Phys. Rev. C 67, 015807 (2003)
S. Goriely, ULB
Nuclear Level Density of 180Ta
180Ta1+
2+
9- 75.342
0
181Ta7/2+
9/2-, 7/2-, 5/2-
E1
s-waveneutron
T1/2 > 1.2×1015y
T1/2=8.152h
s-waveneutron
4+, 3+
…
5-, 4-, 3-, 2-
…8+
6+
7-
5-
179Ta(7/2+)
T1/2=1.82y
Incident γ-ray
181Ta (Target)ElectronCapture
0.24
0.58180Hf
93keV 2+
0+
β- decay
0.03
0.15180W
2+
0+
104keV
per 1 decay of 180Tags
93keV γ-ray 4.665%
55.8keV Kα1 33.12%
54.6keV Kα2 19.20%
T1/2>1.2×1015yT1/2=8.152h
75keV 9-
1+(gs)180Ta
7.576MeV
σm
σgs
σtotal
σm = σtotal - σgs
181Ta(γ,n)180TaProgress of the reactions
Experimental Set-up
Target Sample�181Ta 3He Proportional Counter ×20
Neutron Moderator ; Polyethylene
�197AuTarget Sample
NaI(Tl) Scintillator
180Tags → 180Hf �Electron Capture
0
20
40
60
80
100
120
Counts / h / 230 eV
Ephoton
[keV]50.0 55.0 60.0 65.0 70.0
Kѓ ї1
Kѓ ї2
Kѓ А 100
1000
0 5 10 15 20 25Counts / h
Time[h]
λexp =0.084λnominal=0.085
Experimental results, and comparison with theoretical models
Present work (2006)Combinatorial NLD model
Systematicuncertainties
10�26%
0.1
1
10
100
7 8 9 10 11 12 13 14
Cross Section [mb]
Eγ[MeV]
181Ta(γ,n)180Ta
181Ta(γ,n)180Tam
IAEA : Lee et al. (1998)
Statistical NLD model
Goko et al. Phys. Rev. Lett. 96, 192501 (2006)
HF model calculations by S.Goriely (ULB)
10-2
10-1
100
101
102
103
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 0.1 1 10
Cros
s Se
ctio
n [m
b]
σm/σ
tot
En[MeV]
Present results
for the s-process 180Tam production
30keV(s-process)
0.04
Previous Predictions
0.02�0.09 (K.Yokoi, K.Takahashi ;1983)0.043±0.008 (Zs. Nèmeth, F.Käppeler, G.Reffo ;1992)
Combinatorial NLD model
σm/σtot�σm� 44mb (Zs. Nèmeth, F.Käppeler, G.Reffo ;1992)
Goko et al. Phys. Rev. Lett. 96,
192501 (2006)
Statistical NLD model
mbmn 2290 ±=γσ
at 30 keV
01.004.0 ±=totn
mn
γ
γ
σσ
HF model calculations by S.Goriely (ULB)
mTanTa 180179 ),( γ
totn
mn
γ
γ
σσ
mnγσ
σnγ (E) =πkn
2 gJ
Tγ (E,J,π ) Tn (E,J,π )TtotJ ,π
∑
Tγ (E,J,π) = TXλν (εγ )
ν ,X ,λ∑ + TXλ (εγ ) ρ(E −εγ )dεγ∫
X ,λ∑
Total γ transmission coefficient
TXλ (εγ ) = 2πεγ2λ +1 fXλ (εγ ) ↓
γ‐ray strength function nuclear level density ρ( E − εγ )
X=E, Mλ=1, 2, …
neutron resonance spacinglow‐lying levels
Hauser-Feshbach model cross section for AX(n,γ)A+1XHauser-Feshbach model cross section for AX(n,γ)A+1X
After integrating over J and π
≅πkn
2 gJTγ (E,J,π)J ,π∑
Ttot ≈ Tn (E,J,π)
n+AX
A+1X
E, J, πAX(n,γ)A+1X A+1X(γ,n)AX
12)(
)()( 2
12
+↑=
+−
λεσ
πε
ε γλλ
γγλ
absX
X cf
εγ < Sn εγ > Sn
Photoneutron emissionRadiative neutron capturecontinuum
Df X
X
)()( )12( γλλ
γγλ
εεε
Γ↓= +−
(n,γ) and (γ,n) are interconnected through the γ-ray strength function and the nuclear level density in the Hauser-Feshbach model.
Brink Hypothesis fXλ (εγ ) ↑≅ fXλ (εγ ) ↓
Experimental determination of γ‐ray strength function
εγ < Sn(γ, γ’) NRF dataParticle‐γ coin. data
(Oslo Method)
Sn
GDR
A‐1A‐1 AA
PDR, M1
εγ > Sn(γ.n) data
A‐1X(n, γ)AX Statistical model calculation of A‐1X(n, γ)AX cross sections with experimental γSF
A+1A+1 A+2A+2
(γ,n)
known (n, γ)
A‐1A‐1 AA
(γ,n)
GDR
Sn
PDR, M1
1. εγ > Sn(γ.n) data
2. εγ < SnExtrapolation by microscopic model
Theoretical extrapolation of γ‐ray strength function
3. Justification of γSF by reproducing known (n,γ) cross sections in the Hauser‐Feshbach model calculation
Statistical model calculation of A+1X(n,γ)A+2X cross sections with experimentally‐constrained γSF
γ‐ray Strength Function Method
Indirect determination of (n, γ) cross sections for unstable nuclei based on a unified understanding of (γ,n) and (n, γ) reactions through the γ‐ray strength function
The best understanding of the γ SF with PDR and M1 resonance is obtained by integrating
• (γ, n) data• (γ, γ’) NRF data • Particle‐γ coin. data , Oslo Method• Existing (n, γ) data
H. Utsunomiya et al., Phys. Rev. C 80, 055806 (2009)
1. Nuclear Astrophysicss‐process branch‐point nuclei: unstable nuclei along the line of β‐stability
63Ni, 79Se, 81Kr, 85Kr, 95Zr, 147Nd, 151Sm, 153Gd, 185W
2.Nuclear Data for Nuclear Engineeringnuclear transmutation of long‐lived fission product
79Se, 93Zr, 107Pd etc.
F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011)
Applications of the γ‐ray Strength Function Method
66Sn 116 117 118 119 12012127 h 122
123129 d 124
105 106107
6.5 106 y 108Pd
90 91 9293
1.53 106 y 949564 d 96Zr
77 7879
2.95 103 y 80Se 7675120 d
893.27 d
104
66115
Applications LLFP (long lived fission products)nuclear waste
Astrophysical significancePresent (γ,n) measurementsExisting (n,γ) 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)
F. Kitatani, Ph.D. thesis, to be published
(n,γ) c.s. to be deduced
H.U. et al., PRC88 (2013)
6
5
7
In collaboration with Univ. Oslo etc.
In collaboration with ELI‐NP etc.
Sn isotopes
HFB+QRPA E1 strength supplemented with a pygmy E1 resonance in Gaussian shape
Eo ≈ 8.5 MeV, Γ≈ 2.0 MeV, σo ≈ 7 mb
� 1% of TRK sum rule (E1 strength)
γSF for Sn isotopes
(γ,n) dataH. Utsunomiya et al., PRC84 (2011)
Oslo data(3He, αγ�, (3He, 3He’ γ�Toft et al., PRC 81 (2010); PRC 83 (2011)
121Sn[T1/2=27 h]
123Sn[T1/2=129 d]
Uncertainties: 30‐40%
Uncertainties: a factor of � 2
(n,γ) CS for unstable Sn isotopes
(γ,n) dataH. Utsunomiya et al., PRC 88 (2013)
Oslo data(3He, αγ�, (3He, 3He’γ�M. Guttormsen et al., PRC71 (2005)
(γ,γ’) dataG. Rusev et al., PRC77 (2008)
Mo isotopes
ELI‐NP (Europe) (Extreme Light Infrastructure‐ Nuclear Physics)
Magurele‐Bucharest, RomaniaApproved by the European Commission in 2012 First Experiments in 2018
Eγ = 0.2 -19 MeVIγ≥ 1011 (s-1 mm-2 mrad-2 0.1%-1)ΔE/E ≤ 0.5%
I. Physics and Experiments with a 4π Neutron Detector
Physics
Rare isotope measurements for the p‐process nucleosynthesis
p-nuclei are very rare.
• Highest intensity and monochromatic γ‐ray beam
• 1mg samples of rare isotopes
Production vs Destruction
181Ta(γ,n)180Ta 180Ta(γ,n)179Ta 139La(γ,n)138La 138La(γ,n)137La
measured! Not so ever
H. Utsunomiya et al., PRC67, 015807 (2003)
Rarest element Only naturally-occurring isomer
20 3He proportional countersembedded in polyethylene moderator Triple‐ring configuration1st ring of 4 counters2nd ring of 8 counters3rd ring of 8 counters
180Ta(γ,n) & 138La(γ,n) measurement
Day 1 Experiment #1
4π Neutron Detector
Resonances above Sn
207Pb(γ,n) 208Pb(γ,n)
C.D. Berman et al., PRL25, 1302 (1970)R.J. Baglan et al., PRC3, 2475 (1971)
Threshold Photoneutron TechniqueBremsstrahlung + n‐TOF
Liquid Scintillation and LaBr3(Ce) Detector Array
62
LaBr3(Ce), 3” x 3”
34
PDR and M1 resonance in 207Pb ‐ 207Pb(γ,n) measurement ‐
Day 1 Experiment #2
Exclusive neutron decays of GDR in 159Tb
• 159Tb(γ,xn) x= 1, 2, 1g/cm2
• Sn = 8.133 MeV
• S2n = 14.911 MeV
159Tb
n+ 158Tb
2n+ 157Tb
in collaboration with Vladimir Varlamov
Eγ(max) = 19 MeV σ(γ,2n)
σ(γ,n)
IAEA –TECDOC‐1178
Day 1 Experiment #3
Summary
• Photonuclear reactions had a glorious days in 1950 through 1980 in the study of GDR with the γ‐ray source of positron annihilation in flight. Then, they have slowly faded away toward 1990.
• Photonuclear reactions have revised with the new γ‐ray source of laser inverse Compton scattering in the context of nuclear astrophysics at the turn of the 21st century.
• ELI‐NP will open up a new era of photonuclear reactions in nuclear science with intense laser and γ‐ray beams.
Personal view of the photonuclear reaction study
Recommended