| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a short arc discharge tube having a prolonged life by improving the brightness of a doped type cathode and employing the cathode for the short arc discharge tube. SOLUTION: This cathode for a short arc discharge tube is provided with a doped type cathode 1 of an oxide containing at least barium, and doped and sharpened at the tip and a cap 3 covering the surface of the doped cathode and is sealed in a glass tube while being set face to face to an anode. The cap 3 has a work function higher than that of the doped cathode 1 and is made of a heat resistant metal, carbide, nitride, or their mixture and a through-hole 3a with a approximately same size as that of the cathode bright point is formed at the point corresponding to at least the tip of the doped cathode 1 to project the tip of the doped cathode 1 from the through-hole 3a.</p> |
