First observation of Smith-Purcell radiation from relativistic electrons

Abstract

A beam of 3.6-MeV electrons has been used to study the generation of radiation in the far infrared (FIR) by the Smith-Purcell mechanism. The dependence of wavelength on angle of emission, over angles from 56\ifmmode^\circ\else\textdegree\fi{} to 150\ifmmode^\circ\else\textdegree\fi{} and wavelengths from 350 to 1860 \ensuremath{\mu}m, is in excellent agreement with the Smith-Purcell dispersion relation. Comparison of the yield with that from a 5000-K source suggests that the spontaneous Smith-Purcell effect offers an easily tunable alternative to the synchrotron as a coherent FIR source, and that it could also form the basis of an inexpensive, compact free-electron laser.