An X-ray tube of an embodiment includes an anode; and an electron emission device. In an embodiment, the electron emission device includes at least one electron emitter including at least one emission surface and at least one barrier grid, the at least one barrier grid being spaced apart from the at least one emission surface of the electron emitter and includes a definable number of individually controllable grid segments. According to an embodiment, at least one individually definable grid voltage is applicable to each of the grid segments. In a simple manner, an electron-emission device of an embodiment permits the image quality to be adjusted with minimal anode loading.

A gas field ionization source for forming an electric field for ionizing gas comprises: an emitter tip having a tip end; an extraction electrode facing the emitter tip and having an aperture at a position distant therefrom; a gas supply means for supplying the gas in the vicinity of the emitter tip; a vacuum partition made of a metal having a hole; and a high voltage power source for applying voltage between the emitter tip and the extraction electrode. The hole is constructed so that the tip end of the emitter tip can pass therethrough and the vacuum partition has a micro protrusion, around the hole, protruding toward a side of the extraction electrode.

A gas field ionization source for forming an electric field for ionizing gas comprises: an emitter tip having a tip end; an extraction electrode facing the emitter tip and having an aperture at a position distant therefrom; a gas supply means for supplying the gas in the vicinity of the emitter tip; a vacuum partition made of a metal having a hole; and a high voltage power source for applying voltage between the emitter tip and the extraction electrode. The hole is constructed so that the tip end of the emitter tip can pass therethrough and the vacuum partition has a micro protrusion, around the hole, protruding toward a side of the extraction electrode.

A field emission cathode device and formation method involves a rotating field emission cathode including a field emission material deposited on a surface thereof, the field emission cathode rotating about an axis and being electrically connected to ground, and a planar gate electrode extending parallel to the surface of the rotating field emission cathode and defining a gap therebetween. A gate voltage source is electrically connected to the gate electrode and is arranged to interact therewith to generate an electric field, with the electric field inducing a portion of the surface of the rotating field emission cathode adjacent to the gate electrode to emit electrons from the field emission material toward and through the gate electrode.

A field emission cathode device and formation method involves a rotating field emission cathode including a field emission material deposited on a surface thereof, the field emission cathode rotating about an axis and being electrically connected to ground, and a planar gate electrode extending parallel to the surface of the rotating field emission cathode and defining a gap therebetween. A gate voltage source is electrically connected to the gate electrode and is arranged to interact therewith to generate an electric field, with the electric field inducing a portion of the surface of the rotating field emission cathode adjacent to the gate electrode to emit electrons from the field emission material toward and through the gate electrode.

The present invention addresses the problem of providing a device with which it is possible to adjust the focal point of an electron beam both toward a shorter focal point and toward a longer focal point after an electronic gun was fitted on a counterpart device.

The aforementioned problem can be solved by an electron gun including a photocathode, and an anode, the electron gun furthermore comprising an intermediate electrode disposed between the photocathode and the anode, the intermediate electrode comprising an electron-beam passage hole through which an electron beam released from the photocathode passes, and the electron-beam passage hole having formed therein a drift space in which, when an electrical field is formed between the photocathode and the anode due to application of a voltage, the effect of the electrical field can be disregarded.

The present invention addresses the problem of providing a device with which it is possible to adjust the focal point of an electron beam both toward a shorter focal point and toward a longer focal point after an electronic gun was fitted on a counterpart device.

The aforementioned problem can be solved by an electron gun including a photocathode, and an anode, the electron gun furthermore comprising an intermediate electrode disposed between the photocathode and the anode, the intermediate electrode comprising an electron-beam passage hole through which an electron beam released from the photocathode passes, and the electron-beam passage hole having formed therein a drift space in which, when an electrical field is formed between the photocathode and the anode due to application of a voltage, the effect of the electrical field can be disregarded.

An electron gun includes a cathode including an electron emitting portion, an extraction electrode for extracting electrons emitted from the electron emitting portion, and a focusing electrode for focusing the electrons extracted by the extraction electrode. The focusing electrode includes an outside electrode having a tubular shape, and an inside electrode arranged inside the outside electrode. The inside electrode defines a first space having a columnar shape, and includes a first surface on a side of the cathode, and a second surface on an opposite side of the first surface. An inside surface of the outside electrode and the second surface of the inside electrode define a second space. The inside electrode includes an electron passage hole, and a communicating portion which makes the first space and the second space communicate with each other.

A field emission cathode device and method for forming a field emission cathode device involve a cathode element having a field emission surface, and a gate electrode element disposed in spaced-apart relation to the field emission surface of the cathode element so as to define a gap therebetween, with the gate electrode element having a plurality of parallel grill members or a mesh structure laterally-extending between opposing anchored ends. A film element laterally co-extends and is engaged with the gate electrode element, with the film element being arranged to allowed electrons emitted from the field emission surface of the cathode element to pass therethrough, and to cooperate with the gate electrode element and the cathode element to form a substantially uniform electric field within the gap and about the field emission surface.

An X-ray tube of an embodiment includes an anode; and an electron emission device. In an embodiment, the electron emission device includes at least one electron emitter including at least one emission surface and at least one barrier grid, the at least one barrier grid being spaced apart from the at least one emission surface of the electron emitter and includes a definable number of individually controllable grid segments. According to an embodiment, at least one individually definable grid voltage is applicable to each of the grid segments. In a simple manner, an electron-emission device of an embodiment permits the image quality to be adjusted with minimal anode loading.