LIQUID METAL ION SOURCE

PURPOSE:To provide a lifetime sustaining practical service and obtain a stable boric ion beam by forming a needle electrode from tungsten boride containing 40-70at.% W. CONSTITUTION:An ion source according to the present invention includes a needle electrode 1, reserves 2A, 2B, bulkheads 3A, 3B, heaters 4A, 4B, electrodes 5A, 5B, insulating washers 7A, 7B, and metal plates 9A, 9B. On the surface of this needle electrode 1 a boron-containing alloy is borne by liquid, and boric ions are emitted from the tip of this electrode 1 through the action of electric field. The needle electrode 1 consists of tungsten boride containing 40-70at.% W. This provides less ion beam varying rate, and the needle electrode 1 is prevented from erosion due to boron alloy to accomplish stable serviceability for a long period of time.