Coherent Diffraction and Cherenkov Radiation from Short Electron Bunches in Fibers

The ability to use a radiation of relativistic electrons in optical fibers for beam diagnostics was proposed by X. Artu recently *. In the cited work the properties of different types of radiation, such as diffraction and Cherenkov radiation in the visible region, induced in fibers by relativistic electron were considered. In our report we present the results of experimental investigation of such a phenomenon for millimeter wavelength radiation. The origin and properties of radiation in fibers were investigated for different geometries of fiber position in respect to the electron beam. The spectral characteristics and dependence on the orientation angle of fibers relative to the electron beam were investigated. One of the useful properties of fibers is the fiber flexibility. The characteristics of radiation accepted by flexible fiber with diameter D=11 mm and length L=600 mm were investigated as a function of curvature radius of the fiber R. The experimental results show the allowable transport factor of radiation for the condition L>R>>D. We believe that fibers for mm and submm range can be used for beam diagnostics also.