Patent ID: 6882093

Claim:
An electron tube device, comprising: an electron gun that includes a cathode that emits electrons, the cathode including: a base metal whose main component is nickel and that includes magnesium as a reducing agent; an emitter layer whose main component is barium oxide, and that includes a predetermined metal and/or metal oxide as a dopant; and a heater that heats the base metal and the emitter layer, wherein, if a number of moles of barium included in the emitter layer is expressed as 1000, a value obtained by multiplying a number of moles of the predetermined metal and/or metal oxide included as the dopant by a value by which the number of moles of barium was multiplied in order to be expressed as 1000 is expressed as X, a value obtained by multiplying a number of moles of the magnesium included in the base metal by the value by which the number of moles of barium was multiplied in order to be expressed as 1000 is expressed as Y, and when a value of Y and a value of X are expressed as XY coordinates in which the X coordinate is the value of X and the Y coordinate is the value of Y, the value of X and the value of Y are within a range defined by straight lines connecting points (0.7, 6), (0.8, 15), (3, 130), (3, 30), (2.5, 10), (2, 0.1), and (1, 0.1).