Experimental Research on Smith-Parcel Free Electron Laser in Millimeter Wave Region

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The purpose of this research in 1995-1996 is the experimental research on Smith Purcel free electron laser in millimeter wave region.We operated a compact electrostatic accelerator (Disktron) with 1MV voltage. The electron source is photoelectron emission with KrF ultraviolet laser. This conbination of the electron source as well as the accelerator is suitable for precise control of the elctron beam. We successfully obtained the electron beam with 1-4 A peak current, 800KeV energy, and 30ns pulse width. This beam is propageted in the beam line, which is evacuated by a turbmolecular pump and a cryopump. The beam is well controlled by focusing magnets as well as deflection magnets.The theoretical analysis is performed, taking into account the dispersion relation of the electron beam mode and the electromagnetic waves near a metal grating. We design the Smith Purcel free electron laser with theoretical oscillation frequency of 51GHz. The grating pitch is 25mm and the length is 300mm.With aid of the focusing magnetic coils and deflection coils, the electron is carefully controlled to propagate near the grating surface. We observed the radiation from the interaction region with the U band (45-60GHz) detector diode. The power received by the diode is nearly 0dBm.We will continue the experiment. However, we think that what we observe is the 51GHz Smith-Purcel free electron laser oscillation, which is predicted by the theory.