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Dobashi, K.

Paper Title Page
TPPE049 Synchronizaiton Between Laser and Electron Beam at Photocathode RF Gun 3079
 
  • A. Sakumi, A. Fukasawa, Y. Muroya, T. Ueda, M. Uesaka, K. Yoshii
    UTNL, Ibaraki
  • K. Dobashi
    NIRS, Chiba-shi
  • N. Kumagai, H. Tomizawa
    JASRI/SPring-8, Hyogo
  • J.U. Urakawa
    KEK, Ibaraki
 
  The chemical reactions of hot, room temperature and critical water in a time-range of picosecond and sub-picosecond have been carried out by the 18 MeV S-band linac and a Mg photocathode RF gun with the irradiation of third harmonic Ti: Sapphire laser, at Nuclear Engineering Research Laboratory (NERL), the University of Tokyo. Although this short bunch and 100 fs laser light are enough to perform the experiment of radiation chemistry in the time-range of sub-picosecond, the total time-resolution become worse by the instability of synchronization between laser and radio frequency of linac. We found that the fluctuation of room temperature causes the instability, particularly the cycle of turning on/off of the air-conditioner. It is shown that 0.3 °C (peak-to-peak) fluctuation of the laser-room temperature have approximately corresponded to the instability of 6 ps. We are trying to decrease the fluctuation of the room temperature, together with the local temperature stability of the Ti: Sapphire crystal, the pumping laser. Furthermore, we will develop the feed back system for reducing the instability of the synchronization.  
WPAP019 X-Band Thermionic Cathode RF Gun at UTNL 1646
 
  • A. Fukasawa, F. Ebina, T. Kaneyasu, H. Ogino, F. Sakamoto, M. Uesaka
    UTNL, Ibaraki
  • M. Akemoto, H. Hayano, T. Higo, J.U. Urakawa
    KEK, Ibaraki
  • K. Dobashi
    NIRS, Chiba-shi
  • K.M. Matsuo, H. Sakae
    IHI/Yokohama, Kanagawa
 
  The X-band (11.424 GHz) linac for compact Compton scattering hard X-ray source are under construction at Nuclear Engineering Research Laboratory, University of Tokyo. This linac designed to accelerate up to 35 MeV, and this electron beam will be used to produce hard X-ray by colliding with laser. It consists of a thermionic cathode RF gun, an alpha magnet, and a traveling wave tube. The gun has 3.5 cells (unloaded Q is 8250) and will be operated at pi-mode. A dispenser cathode is introduced. Since the energy spread of the beam from the gun is predicted to be broad due to the continuous emission from the thermionic cathode, a slit is placed in the alpha magnet to eliminate low energy electrons. The simulation on the injector shows the beam energy 2.9 MeV, the charge 23 pC/bunch, and the emittance less than 10 mm.mrad. The experiment on the gun is planed in the beginning of 2005, and the details will be discussed on the spot.  
RPAP006 X-Band Linac Beam-Line for Medical Compton Scattering X-Ray Source 994
 
  • K. Dobashi
    NIRS, Chiba-shi
  • M. Akemoto, H. Hayano, T. Higo, J.U. Urakawa
    KEK, Ibaraki
  • F. Ebina, A. Fukasawa, T. Kaneyasu, H. Ogino, F. Sakamoto, M. Uesaka, Y. Yamamoto
    UTNL, Ibaraki
 
  Compton scattering hard X-ray source for 10~80 keV are under construction using the X-band (11.424 GHz) electron linear accelerator and YAG laser at Nuclear Engineering Research laboratory, University of Tokyo. This work is a part of the national project on the development of advanced compact medical accelerators in Japan. National Institute for Radiological Science is the host institute and U. Tokyo and KEK are working for the X-ray source. Main advantage is to produce tunable monochromatic hard ( 10-80 keV) X-rays with the intensities of 108-10 photons/s (at several stages) and the table-top size. Second important aspect is to reduce noise radiation at the beam dump by adopting the deceleration of electrons after the Compton scattering. The X-ray yield by the electron beam and Q-switch Nd:YAG laser of 2.5 J/10 ns is 107 photons/RF-pulse (108 photons/sec in 10 pps). X-band beam line for the demonstration is under commissioning. We also design to adopt a technique of laser circulation to increase the X-ray yield up to 109 photons/pulse (1010 photons/s). The construction of the whole system starts. X-ray generation and medical application will be performed in this year.  
RPAP012 Dual Energy X-Ray CT by Compton Scattering Hard X-Ray Source 1291
 
  • M. Uesaka, T. Kaneyasu
    UTNL, Ibaraki
  • K. Dobashi, M. Torikoshi
    NIRS, Chiba-shi
 
  We have developed a compact Compton scattering hard X-ray source at Nuclear Engineering Research Laboratory, University of Tokyo. The compact hard X-ray source can produce tunable monochromatic hard X-rays. The monochromatic hard X-rays are required in large field of medical and biological applications. We are planning to perform dual-energy X-ray CT, which enables us to measure atomic number Z distribution and electron density re distribution in a material. The hard X-ray source has an advantage to perform dual-energy X-ray CT. The X-ray energy can be changed quickly by introducing a fundamental frequency and a second harmonic frequency lasers. This quick energy change is indispensable to medical imaging and very difficult in a large SR light source and others. The information on the atomic number and electron density will be used for treatment plan in radiotherapy as well as for identification of materials in a nondestructive test. We examined applicability of the dual-energy X-ray CT for atomic number measurement for low to medium Z elements (Z=30) by considering the X-ray profile generated by Compton scattering. Details of the numerical simulations and plans of the dual-energy X-ray CT will be reported in the conference.