Observation of IR spontaneous radiation at LEBRA

The FEL system of the Laboratory for Electron Beam Research and Application (LEBRA) of Nihon University was reconstructed for the infrared region (IR) from 0.8 μm. In order to check the performance, the spontaneous radiations generated by the new undulator were observed using a CCD video camera. It was demonstrated that the wavelength of the visible spontaneous radiations, which correspond to the higher harmonics, can be controlled by adjustment of the undulator gap width. The time, structure of the radiation measured by a photo detector indicates that the yield of the radiation has the linearity to the electron beam current and the undulator generates enough IR radiation. The spectra of the 2nd and 3rd harmonic radiation with much narrow widths were also obtained. These results mean that the new undulator works as an IR photon generator. (author)