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Nakao, K.

Paper Title Page
MOP25 The LEBRA 125 MeV Electron Linac for FEL And PXR Generation 90
 
  • K. Hayakawa, Y. Hayakawa, K. Ishiwata, K. Kanno, K. Nakao, T. Sakai, I. Sato, T. Tanaka
    LEBRA, Funabashi
  • K. Yokoyama
    KEK, Ibaraki
 
  A 125 MeV electron linac has been constructed at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University for Free Electron Laser (FEL) and Parametric X-ray (PXR) generation. Two klystrons feed rf power of approximately 20 MW peak and 20 μsec pulse duration each to an injector and three 4 m accelerating structures. Phase of the rf fed to each component is controlled independently. Two accelerating structures connected with the second klystron and a ninety degrees bending system as a momentum analyzer constitute a magnetic bunching system. Electron bunches of 3 to 4 psec width formed at the injector are compressed to within 1 psec during passing through the magnetic bunching system. Peak current of the electron beam injected to the FEL system installed downstream of the momentum analyzer is expected to be about 50 A. FEL lasing has been achieved at the wavelength range from 1 to 6 mm. Estimated peak power of the extracted FEL light pulse is about 2 MW. Applied researches using the FEL started last autumn. Preliminary experiment for the PXR generation has been continued.  
THP58 Development of C-band High-Power Mix-Mode RF Window 745
 
  • S. Michizono, S. Fukuda, T. Matsumoto, K. Nakao, T. Takenaka
    KEK, Ibaraki
  • K. Yoshida
    MELCO, Hyogo
 
  High power c-band (5712 MHz) rf system (40 MW, 2 μs, 50 Hz) is under consideration for the electron-linac upgrade aimed for the super KEKB project. An rf window, which isolates the vacuum and pass the rf power, is one of the most important components for the rf system. The window consists of a ceramic disk and a pill-box housing. The mix-mode rf window is designed so as to decrease the electric field on the periphery of the ceramic disk. A resonant ring is assembled in order to examine the high-power transmission test. The window was tested up to the transmission power of 160 MW. The rf losses are also measured during the rf operation.  
TUP64 Bunch Length Measurements at LEBRA 411
 
  • K. Yokoyama
    KEK, Ibaraki
  • K. Hayakawa, Y. Hayakawa, K. Nakao, I. Sato, T. Tanaka
    LEBRA, Funabashi
 
  The bunch length of the electron beam from the FEL linac at LEBRA (Laboratory for Electron Beam Research and Application) was estimated from the phase ellipse coefficient which is deduced from the dependence of the beam spread on the accelerating phase. The bunch length of FWHM was estimated approximately 0.33 mm from the results of the experiments. Besides, the pulse length of the FEL lights around the wavelength of 1.5 μm was measured by means of the autocorrelation. The pulse length was less than 0.06 mm according to the number of interfacial waves. These results indicate that the pulse length of the FEL lights isn’t equivalent to the electron bunch length.