X-RAY DEVICE

PURPOSE:To stabilize X-ray output by keeping a focus electrode in grand electric potential, and keeping an electric potential ratio between a cathode and a target constant. CONSTITUTION:In a microfocus X-ray tube 10, impression voltage upon circuits 20 and 30 is carried out by a control device 40. These are incorporated into a cage body 50 of a lead plate 51, and prevent the leakage of an X-ray. An X-ray tube 10 is a combinational body of a metallic envelope 12 and a glass envelope 13. The envelope 12 is electrically conductive, and keeps always grand electric potential. A focus electrode 15d is connected to Thereby, even if electric potential of a target 16a is changed, the shape of an electron lens formed around the electrode 15d becomes always constant, and can keep a stable microscopic X-ray focus. Since an electron gun 15 and the target 16a are surrounded with the envelope 12 in the grand electric potential, the distribution of an electric field inside of the envelope is not disturbed by receiving influenced of an external part. Thereby, X-ray output is stabilized.