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Kawai, M.

  
Paper Title Page
WG111 Featuring the Characteristics of the Super Coherent Terahertz Photon Ring  
 
  • H. Hama, F. Hinode, K. Kasamsook, M. Kawai, T. Tanaka
    LNS, Sendai
  • H. Tanaka
    JASRI/SPring-8, Hyogo-ken
 
  Funding: Grant-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Contract # 17360035

A project of coherent synchrotron radiation source at Terahertz (THz) wavelength region has been developed at Tohoku University, Sendai [1]. The project may involve novel high brightness electron guns employing cathodes of single crystal LaB6 for production of a very short bunch length less than 100 fs [2]. The source has been designed based on isochronous ring optics to preserve the short bunch length, but the ring is not a storage ring. The optics of the racetrack type isochronous ring has resulted from consideration of path length differences due to both the betatron motion and the energy deviation. The coherent THz photons are emitted from circulating electron bunches injected from the linac. Even the beam turns by dipole magnets, the bunch shape does not collapse because of nearly complete isochronous optics of the ring. Since production of the coherent THz radiation requires the bunch length less than 100 fs (stdv, if Gaussian), the maximum path length difference created by passing through the dipoles is controlled to not exceed a couple of tens fs. Predicted spectrum of the Coherent Thz radiation and its characteristics will be also presented.

[1] H. Hama, Proc. the 27th Int. FEL Conf., Stanford, CA, (2005) pp1-6.

[2]T. Tanaka, F. Hinode, M. Kawai, H. Hama, Proc. the 27th Int. FEL Conf., Stanford, CA, (2005) pp142–145

 
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WG412 Low Emittance Electron Guns Employing the LaB6 Single Crystal Cathode  
 
  • H. Hama, F. Hinode, K. Kasamsook, M. Kawai, T. Tanaka
    LNS, Sendai
 
  Funding: Supporting program for universities and related institute by KEK, contract# 3 (2005)

Two different ways to approach low emittance electron beam have been studied at Tohoku University, i.e., independently tunable cells thermionic RF gun and conventional thermionic DC gun employing extremely lower extraction voltage around 50 kV without a grid structure. The specific common feature of these guns is introducing a cathode of single crystal LaB6. Beam of much higher current density can be generated from the LaB6 crystal than that from conventional dispenser cathodes, so that the size of the cathode area is able to be reduced. The 50 kV DC gun is designed so as to drive a Terahertz (THz) free electron laser and it will be very much compact to exclude the high voltage stage. Because the distance between the anode and the wehnelt is very short, the extracting electric field should be very high. On the other hand, a thermionic RF gun with two independently tunable cells has been developing towards femtosecond short bunch beam [1]. By using a simulation code based on finite difference time domain method, effects of wakefield and coherent radiation in a bunch compressing and energy filtering section followed by accelerating structures are evaluated.

[1] T. Tanaka, F. Hinode, M. Kawai, H. Hama, Proc. the 27th Int. FEL Conf., Stanford, CA, (2005) pp142–145

 
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