Photo-Nuclear Physics Experiments by using an Intense Photon Beam Toshiyuki Shizuma Gamma-ray...

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Photo-Nuclear Physics Experiments

by using an Intense Photon Beam

Toshiyuki Shizuma

Gamma-ray Nondestructive Detection Research Group

Japan Atomic Energy Research Institute

238U243Am

0+ 0 0+ 0 0+ 0

21761+

Absorption

Emission

Energy [keV]

Flux of gamma-rays

Tunable

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 variable

Small divergent

Electron

Laser light

LCS g ray

Vertical polarization: q=90°

E1: Horizontally scattered

M1: Vertically scattered

LCS beam

Physics with LCS Photon Beams

Nuclear physics

Fundamental 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

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)

Eth ～ 8MeV

～ 15MeV

PDRM1Sc

(g,n)(g,g')

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 850

transiton 1 for 850

M..Asym

4.5 5.0 5.5 6.0 6.5 7.0 7.5–1

–0.5

Energy (MeV)

6500 7000 75000

Energy (keV)

= 0parallel

perpendicular

M1 transitions

6.5 7.0 7.5

Parallel

Perpendicular

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

0 - ,1-

185W3/2-

11/2+ 197

s-wave

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

186Re1-

p-wave

s-wave

0 - ,1-

185W3/2-

11/2+ 197

s-wave

0 - ,1-

185W3/2-

11/2+ 197

s-wave

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

186Re1-

p-wave

s-wave

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

186Re1-

p-wave

s-wave

Neutron TOF Spectrum

Obtained by using LCS g rays at NewSUBARU

2600 2700 2800 2900100

Energy

Structures are observedPrel

Neutron energyLCS g

sNeutrons

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

En (MeV)

Estimation

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

Scattering cross section

Production yield

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

Counting rate

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

Photo-Nuclear Physics Experiments by using an Intense Photon Beam Toshiyuki Shizuma Gamma-ray...

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