Generation of Terahertz Waves Using Ultrashort Electron Beams from a Photocathode Radio-Frequency Gun Linac

Ultrashort picosecond or femtosecond electron beams are useful for electromagnetic radiation production in the terahertz THz range because the inverse of a 1 ps bunch length corresponds to a frequency of 1 THz. The electron beams were generated by a photocathode radio-frequency RF gun linac. Electron beams with an energy of about 4 MeV at the RF gun exit were accelerated to about 30 MeV in a linac. The accelerated electron beams were compressed by a magnetic bunch compressor, resulting in femtosecond pulse width. THz radiation of the order of 0.1 THz based on coherent Cherenkov radiation CCR using hollow dielectric tubes and Smith-Purcell radiation SPR using a metallic grating or metasurface are described.