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Uesaka, M.

Paper Title Page
WEPCH166 Beam Test of Thermionic Cathode X-band RF-gun and Linac for Monochromatic Hard X-ray Source 2319
 
  • K. Dobashi, A. Fukasawa, M. D. Meng, T. Natsui, F. Sakamoto, M. Uesaka, T. Yamamoto
    UTNL, Ibaraki
  • M. Akemoto, H. Hayano, T. Higo, J. Urakawa
    KEK, Ibaraki
 
  A compact hard X-ray source based on laser-electron collision is proposed. The X-band linac is introduced to realize a very compact system. 2MeV electron beam with average current 2μampere at 10 pps, 200 ns of RF pulse is generated by a thermionic cathode X-band RF-gun. Beam acceleration and X-ray generation experiment by the X-band beam line are under way.  
WEPCH182 Design of 9.4 GHz 950 keV X-band Linac for Nondestructive Testing 2358
 
  • T. Yamamoto, T. Natsui, M. Uesaka
    UTNL, Ibaraki
  • M. Akemoto, S. Fukuda, T. Higo, M. Yoshida
    KEK, Ibaraki
  • K. Dobashi
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken
  • E. Tanabe
    AET Japan, Inc., Kawasaki-City
 
  Mobile "suit-case-sized" x-band (9.4GHz) 950 keV linac is designed for applications of nondestructive testing (NDT). Conventional device for the purpose is the S-band linac, but its drawback is a rather large device-size, large electron beam spot size of about 3 mm and lack of spatial resolution. We aim to realize the smaller spot size about 500 micro-m by a low emittance beam. The proposed system consists of the 9.4 GHz magnetron, modulator, thermionic RF electron gun and 9.4 GHz x-band linac and metal target for x-ray generation. The energy at the gun is 20 keV, and the final energy becomes 950 keV. Now, we are designing the linac structure of the pai/2 mode and analyzing the electromagnetic field (EMF) by SUPERFISH. At this time, we finish analyzing EMF of regular cavity cells and we are analyzing EMF of total accelerating tube. We have finished the detailed RF design. Further, we are also performing the design of the pai mode and going to discuss the advantages and drawbacks between them. Construction of the RF supplying system is underway. The detailed design parameters and updated status of the construction are presented at the spot.  
WEPLS028 Improvement of Electron Generation from a Laser Plasma Cathode through Modified Preplasma Conditions Using an Artificial Prepulse 2448
 
  • K. Kinoshita, T. Hosokai, K. Kobayashi, A. Maekawa, T. Ohkubo, T. Tsujii, M. Uesaka
    UTNL, Ibaraki
  • A. Yamazaki
    KURRI, Osaka
  • A.G. Zhidkov
    NIRS, Chiba-shi
 
  We have been studying the effects of laser prepulses, plasma cavity formation, wave breaking processes in the laser plasma acceleration. It is important to control the preplasma conditions, so as to stabilize the laser plasma acceleration. The modification of the conditions of the laser plasma interaction through an artificial prepulse, magnetic fields, and/or gas density modulation will affect on the characteristics of accelerated electron beams. As the first step, we carry out experiments with an artificial prepulse. If a shockwave driven by the artificial prepulse matches the main pulse foccal position, localized wave breaking may occur effectively, and consequent electron generation will be enhanced. We use a pulse with 10% energy of the main pulse and 300 ps duration to be focused on the interaction point of the gas jet, to change the plasma distribution there. Using the single-shot diagnosis, we investigate the mechanism and technique to improve the properties of electron beams. We observed a strong correlation between the generation of monoenergetic electrons and optical guiding of the main pulse, during the interaction of 11 TW 37 fs laser pulse and He gas jet.  
WEPLS029 Monoenergetic 200fs (FWHM) Electron Bunch Measurement from the Laser Plasma Cathode 2451
 
  • A. Maekawa, T. Hosokai, K. Kinoshita, K. Kobayashi, T. Ohkubo, T. Tsujii, M. Uesaka
    UTNL, Ibaraki
  • Y. Kondo, Y. Shibata
    Tohoku University, Sendai
  • T. Takahashi, A. Yamazaki
    KURRI, Osaka
  • A.G. Zhidkov
    NIRS, Chiba-shi
 
  A laser plasma accelerator is the most promising approach to compact accelerators that can generate femtosecond electron bunches. It is expected that the electron bunch duration less than 100fs can be achieved owing to the high frequency of plasma waves. Since the time-resolution of the fastest streak camera is only 200fs, we have to use the coherent transition radiation (CTR) measurement or E/O (electro-optical) method. We plan to perform a single-shot measurement by getting the whole CTR spectrum by a IR polychromator in near future. As the first step forward it, we used a IR bolometer with different filters and obtained the average spectrum. We can generate monoenergetic electron bunches in the condition of laser intensity 3x1019W/cm2 and electron density 6x1019cm-3. The charge is estimated to be about 10pC using ICT (Integrated Current Transformer). The electron bunch accelerated by plasma waves penetrates 300um Ti-foil, and transition radiation is emitted. We measure CTR spectrum using a bolometer. Spectrum distribution of CTR depends on the electron bunch distribution, therefore we can evaluate the bunch duration from it. In the experiment, bunch duration can be estimated.  
WEPLS053 RF Design of a Cartridge-type Photocathode RF Gun in S-band Linac 2499
 
  • H. Moritani, Y. Muroya, A. Sakumi, T. Ueda, M. Uesaka
    UTNL, Ibaraki
  • H. Hanaki, N. Kumagai, S. Suzuki, H. Tomizawa
    JASRI/SPring-8, Hyogo-ken
  • J. Sasabe
    Hamamatsu Photonics K.K., Hamakita, Shizuoka
  • J. Urakawa
    KEK, Ibaraki
 
  A cartridge-type photocathode RF gun is under development in collaboration with SPring-8 and Hamamatsu Photonics. Each type of cathode (Cs2Te, Mg, diamond, Ag-Cs-O) is sealed in a cartridge-type vacuum tube. Several tubes can be installed in a vacuum chamber. The cathode in the tube is inserted into a center hole in the back plate of the RF gun by a vacuum manipulator. These cartridge-type photocathodes with high QE or sensitivity for visible lights, which are prepared in a factory, can be used for a long time without vacuum breaking. Since a load-lock system for forming a new high QE film is not needed, the cartridge-type RF gun becomes compact. We are going to introduce this cartridge-type system to our linac with the BNL-GUN-IV RF gun this summer. Now, we are calculating the gun parameters of the transmission cavity which has a back plate with a center hole 8mm in diameter with SUPERFISH and simulating the beam dynamics after modifying the beam line to install the system with PARMELA. We aim to use reliable Mg and high-QE Cs2Te and try diamond and Ag-Cs-O for radiation chemistry applications. The detailed numerical design and construction will be presented.