PhotoNuclear Physics Experiments by using an Intense Photon

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. M 1 Laser light Electron E 1 LCS g ray Highly monochromatic Highly polarized (linearly/circularly) Energy variable Small divergent m S LC a be Vertical polarization: q=90° E 1: Horizontally scattered M 1: Vertically scattered

Physics with LCS Photon Beams Nuclear physics Fundamental collective motions via E 1 and M 1 excitation Pygmy dipole resonance, spin-flip M 1, 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 Reliable nuclear model, e. g, shell model predicting M 1 response K. Langanke et al. , PRL 20501 (2004)

Strength Distribution of Dipole Excitation GDR Strength NRF (g, g') (g, n) Eth～ 8 Me. V p n GDR n PDR Sc 0 p M 1 PDR En ～ 15 Me. V Eg M 1 p n GDR: Electric giant dipole resonance PDR: Electric pygmy dipole resonance Sc M 1: 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 Parallel M 1 transitions M 1 E 1 Perpendicular E 1 6. 5 7. 0 7. 5 (Me. V) T. Shizuma et al. , Phys. Rev. C 78 061303(R) (2008) • Clear difference observed between different polarization setups • Unambiguous determination of multipole orders (E 1/M 1) • Observation of the detailed level structure below En in 208 Pb --- Tensor force

Measurements above Neutron Emission Energy n Neutron emission Neutron time-of-flight (TOF) method Duration between g pulses and neutron signals Neutron

Neutron TOF Spectrum Structures are observed g Neutrons Pr e lim ina ry Obtained by using LCS g rays at New. SUBARU Time Neutron energy LCS g

Polarization Effects Neutron m S LC a be 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 (Me. V) Assuming detector time resolution = 1 ns and distance = 3 m

Estimation Scattering cross section Is=1. 2 x 10 -22 cm 2 e. V for Eg=10 Me. V and G 0=1 e. V Production yield Y=3. 4 x 105 /sec for I=106 /sec/e. V and Nt=1 g/cm 2 Counting rate R～ 60 cps for e～ 10 -5 (3 m, 1%) and N=20