Radiation from Relativistic Electrons in Periodic Structures "RREPS-15"

Measurement of polarized coherent diffraction radiation from a slit and an edge

9 Sept 2015, 11:45

15m

Oral 4. Diffraction Radiation, Smith-Purcell Effect 4. Diffraction Radiation, Smith-Purcell Effect

Speaker

Dr Yoshitaka Taira (National Institute of Advanced Industrial Science and Technology (AIST))

Description

Diffraction radiation is emitted when an electron beam passes near an edge or interface between two media with different dielectric constants. Theoretical and experimental investigation of diffraction radiation is performing at several electron accelerator facilities. If the wavelength of the diffraction radiation is longer than a pulse width of electron beam, each radiation is coherently enhanced. Sub-millimeter wavelength, so called terahertz radiation, is enhanced by using the sub-picosecond electron beam. In this presentation, we will focus on a polarization state of coherent diffraction radiation (CDR) in the range of terahertz wavelength. We have measured polarized CDR generated from a rectangular slit and an edge (half plane), which their edges are aligned along the horizontal direction, with a terahertz camera and a wire grid linear polarizer. Ring profile of the CDR generated from the slit was observed. The intensity of vertical polarization was higher than the horizontal polarization. An asymmetrical intensity distribution between two lobes, aligned along the vertically polarized direction, was appeared owing to the pre wave (Fresnel) zone effect when the electron beam did not pass through the center of the slit. On the other hand, a single peak intensity distribution, which main polarization component was vertical, was measured from the edge.