Forward Directed Smith-Purcell Radiation from Relativistic Electrons

The requirements for the generation of forward directed Smith-Purcell emission from relativistic electrons are introduced, and the first experimental evidence of this phenomenon is presented. The experiments were conducted with a 2.8 MeV/ c electron beam interacting with a 1 cm period grating. Radiation emitted in two bands with wavelengths ranging from 600 to 650 μm and 1.2 to 1.7 mm were measured. Grating period to wavelength ratios were as high as 16. The measured intensities are higher than that predicted by incoherent emission.