• D. Wu, W. Liu, C.-X. Tang
  TUB, Beijing

The coherent Smith-Purcell radiation (CSPR) has been demonstrated as an efficient technique for measuring the longitudinal profile of beam bunches. To measure the ultrashort beam bunches, the simulations for the measurements using CSPR are anlyzed with tools of three dimensional particle-in-cell simulations and Kramer-Kronig reconstruction. Different parameters such as rms length of beam bunch and profiles of grating are studied. Furthermore, the measurement device based on a Martin-Puplett Interferometer is introduced, in which noises and attenuation can be reduced.

• W. Liu, W.-H. Huang, C.-X. Tang, D. Wu
  TUB, Beijing

Smith-Purcell radiation (SPR) is emitted when an electron passes near the surface of a periodic metallic grating. The radiation wavelength λ observed at the angle θ measured from a direction of surface grating is determined by λ=D/|n|(1/β cosθ), Where D is the grating period, βc is the electron velocity, c is the speed of light, and the integer n is the spectral order. This radiation mechanism is widely applicated to THz radiation source, for which can be developed into tunable and compact one. In this paper, the radiation characteristics of terahertz (THz) SPR generated from the ultrashort electron beam are analyzed with the three-dimensional particle-in-cell simulation. For obtaining the intense THz radiation, the grating parameters and that of ultrashort electron beam are optimum. The radiation power and energy are obtained by the PIC simulation. The band width of train bunches is compared with that of single bunch. The formation factors including the longitudinal and transverse are calculated. Through this study, we observe that the radiation power is enhanced and the band width can be adjusted.