Experimental study of the compact FEL with the electrostatic accelerator and the micro wiggler in the short millimeter wave region

A compact FEL for sub-mm and far infrared regions is studied at the Institute of Space and Astronautical Science. The FEL can be made compact by using an electrostatic accelerator and a micro wiggler. The FEL has tabletop size with the total length of 2.5 m. At a preliminary phase, we aim to oscillate the FEL in the short mm (millimeter) wave. A photo cathode is used as a source of an electron beam. The electron beam was injected into a FEL resonator consisting of a waveguide and Distributed Bragg Reflectors (DBRs). Stimulated emission was observed with the center frequency of 96 GHz and the peak power of 3.4 mW. The bandwidth of this emission was much narrower than that of the spontaneous emission. The one pass gain of FEL is estimated from the detected waveform of the mm wave.