Abstract: An X-ray tube comprising an anode having a target surface radiating X-rays from a position of an X-ray focal spot by impingement of an electron beam, a focusing electrode and cathodes. The focusing electrode has a bottom portion positioned facing the target surface of the anode and most remote from the X-ray focal spot, at least one inclined wall surface obliquely ascending from the bottom portion in the direction of the anode, and substantially rectangular focusing recesses formed at the inclined wall surface. Each of the cathodes emits electron beams, positioned respectively in the focusing recesses of the focusing electrode. The focusing recess has first and second corners which curve from at least one end wall facing the end of the cathode to two side walls along the direction of the longer side of the cathode, and the first corner located remote from the bottom portion is gentler than the second corner located adjacent to the bottom portion with reference to condition of curving.

Abstract: An X-ray tube is provided with a target that radiates primarily the characteristic X-ray of molybdenum. The target has an electron focal area of molybdenum base alloy containing molybdenum as a major component, and at least one of titanium and a combination of potassium oxide and silicon dioxide.