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) Fingerprint of isotopes WANTED High energy g rays are used; High penetrability Applicable for identification of materials such as specific nuclear materials, explosives, etc. shielded by heavy metals R.Hajima, et al., J. Nucl. Sci. Tech. 45, 441 (2008). Laser Compton Scattering g Rays LCS g rays can be generated by scattering of high energy electrons with laser light. M1 Laser light Electron E1 LCS g ray Highly monochromatic Highly polarized (linearly/circularly) Energy variable Small divergent Vertical polarization: q=90° E1: Horizontally scattered M1: Vertically scattered 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 A. I. Titov and M. Fujiwara, J. Phys. G 32, 1097 (2006) 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 nn BGT0 Reliable nuclear model, e.g, shell model predicting M1 response K. Langanke et al., PRL 20501 (2004) Strength Distribution of Dipole Excitation GDR Strength NRF (g,g') (g,n) Eth～8MeV p n GDR n PDR Sc 0 p M1 PDR En ～15MeV Eg M1 p n p n GDR: Electric giant dipole resonance PDR: Electric pygmy dipole resonance Sc M1: Magnetic spin-flip dipole mode Sc: Magnetic dipole scissors mode (orbital part) p n NRF Measurements with LCS Photon Beam Obtained by using LCS g rays at AIST, Tsukuba, Japan =M1 0 parallel Parallel Counts / 2 keV 400 Asym. M1 transitions 0.85 for M1 transiton 0.85 for E1 transition 200 M1 0 1000 perpendicular Perpendicular = 90 E1 E1 500 0 6500 6.5 7000 7.0 Energy (MeV) (keV) 7500 7.5 T. Shizuma et al., Phys. Rev. C 78 061303(R) (2008) •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 Measurements above Neutron Emission Energy 3+ 11/2+ 0 -,1- 197 n s-wave E1 186W 314 3/2 -,5/2-,7/2174 3- 99 s-wave 186Re Sn=7395keV 185W p-wave 4- 1Sn=7194keV 3/2- Duration between g pulses and neutron signals 0+ Neutron E1 Neutron emission Neutron time-of-flight (TOF) method 187Re 5/2+ Neutron Neutron TOF Spectrum Obtained by using LCS g rays at NewSUBARU 10 5 10 3 Structures are observed g 10 2 10 1 Neutrons Counts per Channel 10 4 Neutrons 10 0 2600 2700 2800 2900 Energy Time Neutron energy LCS g Polarization Effects Neutron K. Horikawa et al., JPS meeting, Sep. 2010 Summary •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 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. TOF Energy Resolution 1 0.9 0.8 DE/E (%) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.2 0.4 0.6 0.8 1 1.2 En (MeV) Assuming detector time resolution = 1 ns and distance = 3m Estimation Scattering cross section 2J 1 Is 2J 0 1 2 c G0 E g Is=1.2x10-22 cm2 eV for Eg=10 MeV and G0=1eV Production yield Y INt Y=3.4x105 /sec for I=106 /sec/eV and Nt=1g/cm2 Counting rate R NY R～60 cps for ～10-5 (3m, 1%) and N=20
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