Emitter (3) and target (7) are arranged so as to face each other in vacuum chamber (1), and guard electrode (5) is provided at outer circumferential side of electron generating portion (31) of emitter (3). Guard electrode (5) is supported movably in directions of both ends of vacuum chamber (1) by guard electrode supporting unit (6). To perform regeneration process of guard electrode (5), guard electrode (5) is moved to opening (22) side (to separate position) by operating guard electrode supporting unit (6), and a state in which field emission of electron generating portion (31) is suppressed is set, then by applying voltage across guard electrode (5), discharge is repeated. After performing regeneration process, by operating guard electrode supporting unit (6) again, guard electrode (5) is moved to opening (21) side (to emitter position), and a state in which field emission of electron generating portion (31) is possible is set.

An emitter, a field emission assembly, and an electromagnetic wave generator are provided, and the emitter is an emitter for emitting electrons in an electromagnetic wave generator and is in the form of a sheet in which a plurality of yarns including carbon nanotube (CNT) fibers are weaved.

The present invention relates to large area field emission devices based on the incorporation of macroscopic, microscopic, and nanoscopic field enhancement features and a designed forced current sharing matrix layer to enable a stable high-current density long-life field emission device. The present invention pertains to a wide range of field emission sources and is not limited to a specific field emission technology. The invention is described as an X-ray electron source but can be applied to any application requiring a high current density electron source.

At least one example embodiment provides an electron emitter apparatus having a first ring of field-effect emitter needles, the field-effect emitter needles of the first ring forming a first emitter surface on an inner side of the first ring; and a second ring of field-effect emitter needles, the field-effect emitter needles of the second ring forming a second emitter surface on an inner side of the second ring, wherein the first ring and the second ring are arranged in such that the first emitter surface and the second emitter surface form a substantially contiguous three-dimensional overall emitter surface, the substantially contiguous three-dimensional overall emitter surface defining a hollow channel along a longitudinal axis of the electron emitter apparatus.

In the present invention, a computed tomography system, an X-ray tube used therein and a cathode assembly disposed in the X-ray tube, as well as an associated method of use, is provided that includes a gantry and the X-ray tube coupled to the gantry. The X-ray tube includes the cathode assembly having a pair of emitters for generating an electron beam, where the pair of emitters are disposed in the casing at angles with respect to one another. The X-ray tube further includes a focusing electrode for focusing the electron beam, an extraction electrode which electrostatically controls the intensity of the electron beam, a target for generating X-rays when impinged upon by the electron beam and a magnetic focusing assembly located between the cathode assembly and the target for focusing the electron beam towards the target.

An emitter (3) and a target (7) are arranged so as to face each other in a vacuum chamber (1), and a guard electrode (5) is provided at an outer circumferential side of an electron generating portion (31) of the emitter (3). The emitter (3) is supported movably in both end directions of the vacuum chamber (1) by the emitter supporting unit (4) having a movable body (40). The emitter supporting unit (4) is operated by an operating unit (6) connected to the emitter supporting unit (4). By operating the emitter supporting unit (4) by the operating unit (6), a distance between the electron generating portion (31) of the emitter (3) and the target (7) is changed, and a position of the emitter (3) is fixed at an arbitrary distance, then field emission is performed with the position of the emitter (3) fixed.

Disclosed is an X-ray generation apparatus for intra-oral X-ray imaging, a guide holder, and an X-ray imaging system comprising the same. The X-ray generation apparatus includes a body and a plurality of X-ray sources disposed in different positions of the body, and configured to irradiate X-rays to a field of view, wherein the body moves along a predetermined trajectory for the field of view.

An X-ray tube has a housing enclosing a vacuum chamber. There is a primary field-emission cathode within the vacuum chamber, a secondary cathode within the vacuum chamber, spaced apart from the primary cathode, and an anode target within the vacuum chamber.

Provided is an X-ray generator including a thermal electron emission type X-ray generator configured to generate a negative high voltage and a filament current, a field electron emission type X-ray generator including an anode electrode to be grounded, and configured to use the negative high voltage to bias the cathode electrode, and a field emission current control unit configured to convert the filament current to generate an output voltage to be provided to a gate electrode of the field electron emission type X-ray generator and convert the filament current to fix, to a specific level, a level of an emission current flowing through the cathode electrode.

The present disclosure provides a method of manufacturing a carbon nanotube electron emitter, including: forming a carbon nanotube film; performing densification by dipping the carbon nanotube film in a solvent; cutting an area of the carbon nanotube film into a pointed shape or a line shape; and fixing the cutting area of the carbon nanotube film arranged between at least two metal members to face upwards with lateral pressure.