X-RAY IMAGE TUBE

PURPOSE:To prevent adhesion of the alkali metal steam to be used at the time of forming a photoelectric surface to a resisting material by composing a potential resistor to be provided in a tube with a cylindrical insulating material and the resisting material formed inside thereof. CONSTITUTION:A potential resistor 21 consists of a cylindrical insulating material 22 and a resisting material formed inside of the insulating material 22. The insulating material 22 is made of ceramic or glass, and the resisting material 23 has a resisting value corresponding to resisting values of R1, R2, R3, R4. This potential resistor 23 is mounted between a first focusing electrode 4 and a second fucusing electrode 5 of a vacuum case 1 of a X-ray image tube. A change of the resisting value of the potential resistor can be prevented without adhesion of the alkali metal steam at the time of forming a photoelectrode surface to the resisting material 23 by using such a potential resistor 21.