An alternative technique for verification of terahertz Smith–Purcell radiation

Abstract

An alternative technique to verify terahertz (THz) Smith–Purcell radiation (SPR) was proposed by using different grating periods. A compact DC electron gun, serving as a THz source, was modified to generate continuous 35 keV electron beam that passes by a metal-coated silicon grating in order to induce SPR. A design on beam optics to generate high-brightness beam was carried out by using Computer Simulation Technology (CST) Studio Suite® software package. The optimization of beam parameters was obtained and experimentally performed. Results show that the root-mean-square (rms) beam size (diameter) is about 1 mm when supplying beam current of 200 µA, and rms beam emittance is about 3π mm mrad. The CST simulation software was, furthermore, employed to observe radiation spectra when using different grating structures. A liquid–helium cooled silicon bolometer together with a low-pass filter was used to detect radiation power. The results reveal that incoherent THz signal with power of 1.5 µW cm−2 is observed when the continuous-beam current is about 200 µA. The dependence of THz frequency and power on the grating period, that is associated to the SPR, was also investigated in this work.