Abstract: The present invention concerns an energy dispersion calibration method for calibrating an electron spectrometer of an electron spectrometer system including at least one electron emission source, electron optics and the electron spectrometer. The method comprising: obtaining, providing or receiving at least one electron energy loss spectrum produced by electrons of the electron spectrometer system exchanging energy with at least one resonant optical mode of an optical resonator into which light at a resonant wavelength is coupled; calculating or providing a Fourier transform of the at least one electron energy loss spectrum or a part of the at least one electron energy loss spectrum; determining or providing an energy dispersion (?E) of the electron spectrometer according to the equation ? ? E = f E ? hc ? ? N ? or ? ? ? E = f E ? E p N .

Abstract: An apparatus for generating Smith-Purcell radiation having at least one spectral component at a wavelength ? includes a periodic structure including a dielectric material and an electron source, in electromagnetic communication with the periodic structure, to emit an electron beam propagating within about 5? from a surface of the periodic structure to induce emission of the Smith-Purcell radiation. The electron beam has an electron energy tunable between about 0.5 keV and about 40 keV so as to change a wavelength of the Smith-Purcell radiation.

Abstract: An apparatus for generating Smith-Purcell radiation having at least one spectral component at a wavelength A includes a periodic structure including a dielectric material and an electron source, in electromagnetic communication with the periodic structure, to emit an electron beam propagating within about 5? from a surface of the periodic structure to induce emission of the Smith-Purcell radiation. The electron beam has an electron energy tunable between about 0.5 keV and about 40 keV so as to change a wavelength of the Smith-Purcell radiation.