Abstract: An X-ray scanning apparatus comprises a number of multi-focus X-ray tubes (25) spaced around an axis X and arranged to emit X-rays through an object on the axis which are detected by sensors (52). Each tube (25) can emit X-rays from a plurality of source positions. In each scanning cycle, in which each of the source positions in each of the tubes is used once, the ordering of the positions used is arranged so as to minimize the thermal load on the tubes (25). This is achieved by ensuring that each source position is non-adjacent to the previously active one and the next active one.

Abstract: An X-ray tube includes an emitter wire (18) enclosed in a suppressor(14, 16). An extraction grid comprises a number of parallel wires (20) extending perpendicular to the emitter wire, and a focusing grid comprises a number of wires (22) parallel to the grid wires (20) and spaced apart at equal spacing to the grid wires (20). The grid wire are connected by means of switches to a positive extracting potential or a negative inhibiting potential, and the switches are controlled so that at any one time a pair of adjacent grid wires (22) are connected together to form an extracting pair, which produce an electron beam. The position of the beam is moved by switching different pairs of grid wires to the extracting potential.

Abstract: An anode for an X-ray source is formed in two parts, a main part and a collimating part. The main part has the target region formed on it. The two parts between them define an electron aperture through which electrons pass to reach the target region, and an X-ray aperture through which the X-rays produced at the target leave the anode. The anode produces at least the first stage of collimation of the X-ray beam produced.

Abstract: An anode for an X-ray source is formed in two parts, a main part and a collimating part. The main part has the target region formed on it. The two parts between them define an electron aperture through which electrons pass to reach the target region, and an X-ray aperture through which the X-rays produced at the target leave the anode. The anode produces at least the first stage of collimation of the X-ray beam produced.

Abstract: An X-ray tube comprises an electron source in the form of a cathodE (12), and an anode (14) within a housing (10). The anode (14) is a thin film anode, so that most of the electrons which do not interact with it to produce X-rays pass directly through it. X-rays can be collected through a first window (16) directly behind the anode (14), or a second window (18) to one side of the anode. A retardation electrode 20 is located behind the anode 4 and is held at a potential which is negative with respect to the anode 14, and slightly positive with respect to the cathode (12). This retardation electrode (20) produces an electric field which slows down electrons passing through the anode (14) so that, when they interact with it, they are at relatively low energies. This reduces the heat load on the tube.

Abstract: An anode for an X-ray source is formed in two parts, a main part (18) and a collimating part (22). The main part (18) has the target region (20) formed on it. The two parts between them define an electron aperture (36) through which electrons pass reach the target region (20), and an X-ray aperture through which the X-rays produced at the target leave the anode. The anode produces at least the first stage of collimation of the X-ray beam produced.

Abstract: An anode for an X-ray source is formed in two parts, a main part (18) and a collimating part (22). The main part (18) has the target region (20) formed on it. The two parts between them define an electron aperture (36) through which electrons pass reach the target region (20), and an X-ray aperture through which the X-rays produced at the target leave the anode. The anode produces at least the first stage of collimation of the X-ray beam produced.