| 摘要 |
PURPOSE:To prevent the scattering of the emitter substance resulting from a spattering, and to increase the releasing electrons by forming a direct heated cathode with an emitter substance spread at the inner surface of a cylindrical heating body, and applying a magnetic field crossing square to the axial direction of the heating body, or an electric field parallel to the axial direction. CONSTITUTION:A direct heated cathode 1 is composed of a cylindrical heating body 2 and an emitter substance 3 spread at the inner surface of the heating body 2, and a voltage is applied to the cathode 1 from a power source 6 between anchors 5, to raise the temperature of the heating body 2 up to the operational temperature of the emitter substance 3. As a result, electrons are emitted from the emitter substance, and released outward by applying a magnetic field in the direction B. Since the heating body 2 is exposed to the external space and the emitter substance is not exposed, in the cathode 1, the spattering effect by positive ions is however reduced, while the number of the electrons drawn out from the cathode 1 is increased. The scattering of the emitter substance resulting from the spattering is therefore reduced and the electron releasing ability is improved. |
