1. γ - MSUnuclphys.sinp.msu.ru/nseminar/16.09.14.pdf · Applications of the reciprocity theorem c. p‐process nucleosynthesis ... Lomonosov Moscow State University (MSU) Skobeltsyn

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

Saclay (France)

Converter target

Annihilation target

Gd‐doped Liquid Scintillation tank

e+ bremsstrahlung (background)

e+‐e‐ annihilation (quasi‐monochromatic)

Subtracted

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%

Experimental Hutch GACKO (Gamma Collaboration Hutch of Konan University)

Table‐top Lasers

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 208Pb

208Pb

207Pb

0+

1‐1/2‐

E1

208Pb

207Pb

0+

1+1/2‐

M1

0= 1=

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

Detection efficiencies

ε //1

ε⊥1

ε 1

ε 0

252Cf sourceε 0ε //

1

ε⊥1

ε 1

MCNP Monte Carlo simulations

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)]

Neutron anisotropy detectorfor E1 & M1 (γ,n) cross section measurements

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


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)


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

Nucleosynthesis of Heavy Elements s‐process, r‐process and p‐process

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


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

Radiative neutron capture ‐ AX(n,γ)A+1X

n + AX

A+1X

E, J, πcontinuum

γSFNLD

decay process

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


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)

(n,γ) CS for Sn isotopes

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

(n,γ) CS for Stable Mo isotopes

(n,γ) CS for Unstable Mo isotopes

93MoT1/2=4000 yr

99MoT1/2=2.75 d

(γ,n) cross sections for Nd isotopes

(n,γ) cross sections for Nd 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

1. γ - MSUnuclphys.sinp.msu.ru/nseminar/16.09.14.pdf · Applications of the reciprocity theorem c. p‐process nucleosynthesis ... Lomonosov Moscow State University (MSU) Skobeltsyn

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