• T. Natsui
  UTNL, Ibaraki
• K. Lee, M. Uesaka
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken
• A. Mori
  University of Tokyo, Tokyo
• F. Sakamoto
  Akita National College of Technology, Akita

We are developing an X-band linac system for monochromatic X-rays source. The monochromatic X-ray is obtained by Compton scattering. Our system has an X-band (11.424 GHz) 3.5-cell thermionic cathode RF gun, traversing wave accelerating tube and a Q-switch Nd:YAG laser with a wavelength of 532 nm. We adopt a laser pulse circulation system. The RF gun can generate multi-bunch electron beam. We aim to generate 1 μs maximum energy electron beam and collide it to circulated laser pulse. I will present a current status of beam measurement of this linac.

• K. Lee, S. Hirai, M. Uesaka, T. Yamamoto
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken
• E. Hashimoto
  JAEA, Ibaraki-ken
• T. Natsui
  UTNL, Ibaraki

Dual energy X-ray system using high energy X-ray from linear accelerator (Linac) applies two times X-ray irradiation which have different energy spectrum each other in many cases. Two different X-rays yield two tomography images which is analyzed through numerical calculation with pixel values for material recognition of a object. However if the X-ray generation is not stable, the results of numerical calculation shows irregular tendency during the inspection. We propose the scintillator array in detection part, because two tomography images are obtained by just one irradiation. That leads to the time saving during inspection and the cost down for additional facilities. The optimal condition is researched to increase the ability of material recognition in interesting materials designing the detector with CsI and CdWO4 scintillators. We focus on the discrimination between heavy materials and light materials with the system in the research. X-ray source is 950 keV X-band Linac we developed for industrial application, which produce pulsed X-ray, 10 pps with around 400 mA beam current.

• H. Tomizawa, H. Dewa, H. Hanaki, S. Matsubara, A. Mizuno, T. Taniuchi, K. Yanagida
  JASRI/SPring-8, Hyogo-ken
• T. Ishikawa, N. Kumagai
  RIKEN/SPring-8, Hyogo
• K. Lee, A. Maekawa, M. Uesaka
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken

We are developing a single-shot and non-destructive 3D bunch charge distribution (BCD) monitor based on Electro-Optical (EO) sampling with a manner of spectral decoding for XFEL/SPring-8. For fine beam tuning, 3D-BCD is often required to measure in real-time. The main function of this bunch monitor can be divided into longitudinal and transverse detection. For the transverse detection, eight EO-crystals surround the beam axis azimuthally, and a linear-chirped probe laser pulse with a hollow shape passes thorough the crystal. The polarization axis of the probe laser should be radially distributed as well as the Coulomb field of the electron bunches. Since the signal intensity encoded at each crystal depends on the strength of the Coulomb field at each point, we can detect the transverse BCD. In the longitudinal detection, we utilize a broadband square spectrum (> 400 nm at 800 nm of a central wavelength) so that the temporal resolution is < 30 fs if the pulse width of probe laser is 500 fs. In order to achieve 30-fs temporal resolution, we use an organic EO material, DAST crystal, which is transparent up to 30 THz. We report the first experimental results of this 3D-BCD monitor.

• K. Koyama
  University of Tokyo, Tokyo
• A. Maekawa, H. Masuda, M. Uesaka
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken
• Y. Oishi
  Central Research Institute of Electric Power Industry, Yokosuka-shi, Kanagawa

We are studying the artificial injection of initial electrons into the wakefield for producing stable electron bunch (the charge is 100 pC, the energy stability is better than a few per cent). The objective of our research is to produce 100-keV class monochromatic X-ray pulses for measuring concentrations of nuclear materials in a reprocessing plant. A K-edge densitometry using monochromatic hard x-ray beams is one of the effective technique to measure concentrations of nuclear materials in a reprocessing solutions. An inverse Compton scattering process between an IR-laser beam of 800 nm and high-energy electron bunch of above 80 MeV makes it possible to deliver tunable monochromatic x-rays near K-absorption edges of nuclear materials of 115-129 keV. In order to use in a reprocessing plant, the equipment for the K-edge densitometry must be smaller than a compact car. The only solution to realize the compact system is to use a laser wakefield accelerator instead of a radio frequency linac. An ultra-short ten-TW laser pulse focused on a supersonic jet makes it possible to accelerate electrons up to 100 MeV in a plasma length of 2.5 mm.

• M. Uesaka, Y. Muroya, T. Ueda
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken
• K. Kanbe, K. Miyoshi
  University of Tokyo, Tokyo

We are commissioning the cathode, Na2KSb at the wavelength of 266, 400 nm with thermo-mechanically modified structure and improved vacuum system (2·10^-08 Pa). We could improve RF reflection waveform and obtain the maximum energy of 22 MeV. We estimate the electrical field of 50 MV at the cathode. So far, we have obtained the quantum efficiencies of 1.1, 0.01% and the maximal charges of 4.6, 1 nC for 266, 400 nm. We are observing and checking carefully individual difference of QE of the cathodes for 266, 400 nm, and we have obtained 22 MeV energy. This new RF photocathode RF gun system has been already used for subpicosecond time-resolved radiation chemistry.