RECIPROCITY THEOREM FOR SMITH-PURCELL RADIATION

Smith-Purcell radiation is produced when a charged particle moves clos e and parallel to a diffraction grating. Calculation of Smith-Purcell spectra is therefore linked to a special gating problem, involving inc ident evanescent waves describing the field of the moving electron. Fo r large period gratings, radiation in the far-infrared and millimetric range is produced, in a spectral range where metallic gratings can of ten be considered as infinitely conducting. In that case, conservation laws and a reciprocity theorem are derived for Smith-Purcell radiatio n by applying techniques from electromagnetic grating theory. (C) 1997 Elsevier Science B.V.