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
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238U243Am
0+ 0 0+ 0 0+ 0
1 680
21761+
Absorption
Absorption
Emission
Emission
24101
12245
++
Energy [keV]
Flux of gamma-rays
Tunable
235U
7/2-
1733
1815
2003
239Pu
1/2+
2143
2423
237Np
0 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
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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
E1
M1
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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
0GTB
K. Langanke et al., PRL 20501 (2004)
A. I. Titov and M. Fujiwara, J. Phys. G 32, 1097 (2006)
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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
Str
engt
h
GDR
0
Eth ~ 8MeV
~ 15MeV
PDRM1Sc
(g,n)(g,g')
En
NRF
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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
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
etr
y
E1
M1
6500 7000 75000
500
1000
0
200
400
= 90
Energy (keV)
Co
un
ts /
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
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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
em
issi
onn
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Neutron TOF Spectrum
Obtained by using LCS g rays at NewSUBARU
2600 2700 2800 2900100
101
102
103
104
105
Cou
nts
perC
hann
el
Energy
Structures are observedPrel
imin
ary
Time
Neutron energyLCS g
Neu
tron
sNeutrons
g
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Polarization Effects
K. Horikawa et al., JPS meeting, Sep. 2010LCS beam
Neutron
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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
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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
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Estimation
Is=1.2x10-22 cm2 eV for Eg=10 MeV and G0=1eV
0
2
0 12
12
E
c
J
JIs
Scattering cross section
Production yield
tNIY
Y=3.4x105 /sec for I=106 /sec/eV and Nt=1g/cm2
Counting rate
NYR
R ~ 60 cps for e ~ 10-5 (3m, 1%) and N=20