Smith–Purcell experiment utilizing a field-emitter array cathode: measurements of radiation

Smith–Purcell (SP) radiation at wavelengths of 350–750 nm was produced in a tabletop experiment using a field-emitter array (FEA) cathode. The electron gun was 5 cm long, and a 25 mm×25 mm holographic replica grating was placed behind the slit provided in the anode. A regulated DC power supply accelerated electron beams in excess of 10 μA up to 45 keV, while a small Van de Graaff generator accelerated smaller currents to higher energies. The grating had a 0.556 μm period, 30° blaze and a 0.2 μm thick aluminum coating. Spectral characteristics of the radiation were measured both manually and automatically; in the latter case, the spectrometer was driven by a stepping motor to scan the wavelength, and AD-converted signals from a photomultiplier tube were processed by a personal computer. The measurement, made at 80° relative to the electron beam, showed good agreement with theoretical wavelengths of the SP radiation. Diffraction orders were −2 and −3 for beam energies higher than 45 keV, −3 to −5 at 15–25 keV, and −2 to −4 in between. The experiment has thus provided evidence for the practical applicability of FEAs to compact radiation sources.