• H. Hama, F. Hinode, M. Kawai, T. Tanaka
  LNS, Sendai

Funding: Supported partly by a Grant-in Aid for Scientific Research from Japan Society for the Promotion of Science, #17360035

As a result of simulation study so far, a specific feature has been found in the longitudinal dynamics in thermionic RF guns. At the beginning of beam extraction, the head of the electrons from a cathode is followed immediately by the electrons just behind, which is extracted by the higher electric field than that at the head of the beam train. Thus later electrons would get velocity faster than the head of the electrons, so that the electrons are expected to concentrates onto the head of the beam under certain conditions such as the gun geometry and the strength of the RF field. In order to investigate this velocity-bunching like effect, a prototype thermionic RF gun was designed and its characteristics have been studied by a 3-D simulation code based on a FDTD (finite difference time demain) method. The gun is consists of two independentlly power feeding S-band RF cavities, and can be operated at modes with different power ratio and phase between two RFs. This paper report the thermionic RF gun is expected to produce several hundreds femtosecond pulse containing approximately 0.1 nC, which may be a powerful tool to generate THz coherent radiation or FELs driver.