photo-nuclear physics experiments by using an intense photon beam
DESCRIPTION
Photo-Nuclear Physics Experiments by using an Intense Photon Beam. Toshiyuki Shizuma Gamma-ray Nondestructive Detection Research Group Japan Atomic Energy Research Institute. Nondestructive Isotope Detection. Nuclear resonance fluorescence (NRF). F ingerprint of isotopes. W A N T E D. - PowerPoint PPT PresentationTRANSCRIPT
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