An alternative technique for verification of terahertz Smith-Purcell radiation

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(R) 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 mu A, and rms beam emittance is about 3 pi 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 mu W cm(-2) is observed when the continuous-beam current is about 200 mu A. The dependence of THz frequency and power on the grating period, that is associated to the SPR, was also investigated in this work.