Photo-Nuclear Physics Experiments

by using an Intense Photon Beam

Toshiyuki Shizuma

Gamma-ray Nondestructive Detection Research GroupJapan Atomic Energy Research Institute

238U243Am0+ 0 0+ 0 0+ 0

1 680

21761+

Absorption

Absorption

Emission

Emission

24101

12245

++

Energy [keV]

Flux of gamma-rays

Tunable

235U7/2-

1733

18152003

239Pu1/2+

21432423

237Np0 0

938

Nondestructive Isotope Detection

Fingerprint of isotopes

W A N T E D

Nuclear resonance fluorescence (NRF)

R.Hajima, et al., J. Nucl. Sci. Tech. 45, 441 (2008).

High energy g rays are used; High penetrability

Applicable for identification of materials such as specific nuclear materials, explosives, etc. shielded by heavy metals

Laser Compton Scattering g Rays

LCS g rays can be generated by scattering of high energy electrons with laser light.

Highly monochromatic Highly polarized (linearly/circularly)Energy variableSmall divergent

Electron

Laser light

LCS g ray

Vertical polarization: q=90° E1: Horizontally scattered M1: Vertically scattered

LCS beam

E1

M1

Physics with LCS Photon Beams

Nuclear physicsFundamental collective motions via E1 and M1 excitation

Pygmy dipole resonance, spin-flip M1, scissors mode, etc

PNC observation with circularly polarized photons

Long-standing question in nuclear physics

Interference between weak-bosons and nucleons

Nuclear astrophysics

Nucelosynthesis (g process and n process)

Inelastic neutrino scattering cross sections

Reliable nuclear model, e.g, shell model predicting M1 response

0GTBnn

K. Langanke et al., PRL 20501 (2004)

A. I. Titov and M. Fujiwara, J. Phys. G 32, 1097 (2006)

Strength Distribution of Dipole Excitation

GDR: Electric giant dipole resonance

PDR: Electric pygmy dipole resonance

M1: Magnetic spin-flip dipole mode

Sc: Magnetic dipole scissors mode (orbital part)

p n

GDR

pnPDR

M1

Sc

p n

p nnp

Eg

Stre

ngth

GDR

0

Eth ～ 8MeV

～ 15MeV

PDRM1Sc

(g,n)(g,g')

En

NRF

NRF Measurements with LCS Photon Beam

• Clear difference observed between different polarization setups• Unambiguous determination of multipole orders (E1/M1)• Observation of the detailed level structure below En in 208Pb --- Tensor force

transition 1 for 850transiton 1 for 850

E.M.

.Asym

4.5 5.0 5.5 6.0 6.5 7.0 7.5–1

–0.5

0

0.5

1

Energy (MeV)

Asy

mm

etry

E1

M1

6500 7000 75000

500

1000

0

200

400

= 90

Energy (keV)

Cou

nts

/ 2 k

eV

= 0parallel

perpendicular

M1 transitions

(MeV)6.5 7.0 7.5

Parallel

Perpendicular

M1

E1

T. Shizuma et al., Phys. Rev. C 78 061303(R) (2008)

Obtained by using LCS g rays at AIST, Tsukuba, Japan

Measurements above Neutron Emission Energy

Neutron time-of-flight (TOF) method

Duration between g pulses and neutron signals

Neutron

Neutron

Sn=

7194

keV

186W

E1

0+

0 - ,1-

185W3/2-

11/2+ 197

s-wave

Sn=

7395

keV

187Re

E1

5/2+

3/2 - ,5/2- ,7/2-

186Re1-

3+

3- 99

1744-

314

p-wave

s-wave

Sn=

7194

keV

186W

E1

0+

0 - ,1-

185W3/2-

11/2+ 197

s-wave

Sn=

7194

keV

186W

E1

0+

0 - ,1-

185W3/2-

11/2+ 197

s-wave

Sn=

7395

keV

187Re

E1

5/2+

3/2 - ,5/2- ,7/2-

186Re1-

3+

3- 99

1744-

314

p-wave

s-wave

Sn=

7395

keV

187Re

E1

5/2+

3/2 - ,5/2- ,7/2-

186Re1-

3+

3- 99

1744-

314

p-wave

s-wave

Neu

tron

emis

sion

n

Neutron TOF Spectrum

Obtained by using LCS g rays at NewSUBARU

2600 2700 2800 2900100

101

102

103

104

105

Coun

tspe

rCha

nnel

Energy

Structures are observedPreli

mina

ry

Time

Neutron energyLCS g

Neu

tronsNeutrons

g

Polarization Effects

K. Horikawa et al., JPS meeting, Sep. 2010LCS beam

Neutron

Summary

The information on the states above the neutron emission energy can be optained through the neutron TOF measurement.- Dipole strength distribution, parity, excitation energy etc.

• Small DE/E (10-6 ～ 10-4): Selective excitation of levels• Short pulse duration: High resolution measurements• High intensity : Increased flight distance →High resolution measurements Rare isotope measurements Less amount of target materials

TOF Energy Resolution

Assuming detector time resolution = 1 ns and distance = 3m

0 0.2 0.4 0.6 0.8 1 1.20

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

En (MeV)

DE/E %

Estimation

Is=1.2x10-22 cm2 eV for Eg=10 MeV and G0=1eV

0

2

0 1212

G

g

Ec

JJIs

Scattering cross section

Production yield

tNIY

Y=3.4x105 /sec for I=106 /sec/eV and Nt=1g/cm2

Counting rateNYR

R ～ 60 cps for ～ 10-5 (3m, 1%) and N=20