We describe a brief history to generate inverse Compton γ-ray beams for science applications. It is discussed that we can open a new field for science developments with a high γ-ray beam, generated by using the coherent inverse Compton scattering.

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In order to improve the laser Corpton γ-ray, the cavity scheme was proposed to increase of interaction lengthof laser and electrons. And nondiffracting laser beam, J₀ Bessel beam, is suggested to take the place ofconventional Gaussian beam to increase the flux of scattered photons through maintaining an efficient interac-tion of electron and laser beam in a long distance. Then, we proposed a Bessel beam cavity to produce andstore the J₀ Bessel beam, and analyzed the propagation features and intensity distribution of the J₀ Bessel beaminside the cavity. The flux of Compton scattering gamma-ray is estirated the oretically and the results revealthat a significant growth are accomplished with the use of J₀ Bessel laser beamcontrasting with the use of Gaussian laser beam. The polarization of gamma-ray is also reported.

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A novel x-ray generation scheme is presented, which is considered to produce attosecond, tunable, coherent xray pulses with high brightness. This scheme is based on a reflection of the incidence laser pulse by a mirror moving at the speed close to that of light. The mirror consists of dense electrons as a breaking wake wave formed by a high-intensity laser pulse. We describe theoretical basis of this flying mirror concept and the proof-of-principle experiment. For comparison, other x-ray generation schemes are also presented.

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Compton scattering of high power laser and electron beams is a good test of electrodynamics in the high field region. Compton scattering occurs in the nonlinear regime if ultra high power laser pulse is scattered. Namely, an electron absorbs multiple laser photons before emitting a single photon with higher energy. In addition to the spectral shift, the theories predict the nonlinear process modifies angular distribution of scattered photons. The author's group measured angular distribution of x-ray photons produced in head-on collision of CO₂ laser and 60-Me V electron beams at Brookhaven National Laboratory, Accelerator Test Facility and confirmed that it agrees with theoretical predictions.

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There were no experimental evidence for existence of a hadron with a quark configuration other than three quarks or a quark-antiquark pair although QCD does not forbid the existence of other combination such as qqqq or qqqqq. Since the LEPS at SPring-8 collaboration reported the first evidence for the Θ⁺ which has a quark configuration of uudds, extensive experimental efforts have been made to confirm the existence of the Θ⁺. In this paper, the experimental study of the Θ⁺ at LEPS together with the experimental situation and the future prospect are reported.

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Laser Compton gamma-ray beam line on a synchrotron radiation facility NewSUBARU supplies polarized high energy photon beam. Photon energy range of quasi-monochromatic spectrum is from 1.7 MeV to 40 MeV. Beam like high energy photons were converted to electron-positron pair beam and measured by imaging plates separated by a magnetic field. Photo nuclear reaction around 17 MeV photon energy was tested to generate fast neutrons. Spectra of the neutrons were measured by a time of flight technique.

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Transmutation of nucleon by gamma-ray is reviewed in this articled. We used the New Subaru storage ring combined with a small solid state laser to get a laser Compton gamma-ray of energies of 10 to 20MeV. Reaction rate of nuclear targets of gold and iodine were obtained by simultaneous measurement of neutron and particles. We show a feasibility of energy balance in gamma-ray transmutation cycle system. Future plant system by this method is also addressed.

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Quasi-monochromatic gamma rays produced through the laser-Compton scattering process (LCS-γays) are quite attractive tools in such various fields, as nuclear physics research, industry diagnostics and therapy in medicine. At AIST LCS-γrays of 1-40 MeV in energy can be obtained on a compact storage ring named TERAS. One major thrust of our researches is applying LCS-γrays to the non-destructive inspection of industrial products composed of high-density materials. Here we report our LCS-γray based computed tomography (CT) technology being developed for this purpose.

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Poly (3-hexylthiophene)/polymethylmethacrylate [P3HT/PMMA] composite thin film was prepared by the spin-coating method by composing a prism-coupled waveguide. The UV-visible spectrum was recorded in the range of 300-900nm to determine its optical absorption property. An Nd: YAG laser with a wavelength of 1064nm, a pulse width of 5ns, and a repetition frequency of 10Hz was used for optical bistability measurements. The optical bistable characteristics of the prism-coupled waveguide comprised of P3HT/PMMA composite thin film was measured for different input laser power intensity using optical bistable measuring equipment. The effect of organic gas treatment on the optical bistable behavior of the P3HT/PMMA quasi-waveguide was observed. The effect of PMMA molecular weight on the optical bistability of the P3HT/PMMA waveguide was also investigated.

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