Patent GB-640694-A (GB)
Title: Improvements in x-ray apparatus
IPC: H01J35/30
Filed: 1945-06-11
Abstract: 640,694. X-ray tubes; electron lenses. WATERTON, F., and METROPOLITANVICKERS ELECTRICAL CO., Ltd. June 11, 1945, No. 14732. [Class 39 (i)] X-ray apparatus comprises an evacuated envelope arranged for rotation about the anodecathode axis within a stationary housing containing cooling liquid and an anode forming part of the surface of the envelope and provided with vanes which when the envelope is rotated operate to circulate the cooling liquid around the envelope and over the exterior surface of the anode, focusing means being provided which maintain the electron beam stationary and inclined to the anode-cathode axis so that it impinges upon the rotating anode over an extensive annular target area. The cup-shaped anode 26 is mounted on a reentrant glass member 7 and impeller vanes 26<SP>1</SP> attached to the anode 26 enforce circulation of cooling mineral oil, cooled by the heat abstracting cooling coil 35, through the tubular baffle 36 supported from the conductor 31 by radial vanes 37, the conductor 31 having an electrical butt contact 32 urged by spring 33 into frictional engagement with the rotating contact 34 supported by the anode and being electrically connected to an insulator 30 through which passes a conductor from the anode to the terminal 29. The anode consists of a shell of copper, a ring of tungsten 27 and one or more coaxial rings of chromium, iron, a ferrous alloy or copper on to which the electron beam moves in succession by altering the orientation or excitation of the electromagnetic coil 28. Focusing of the beam to form a line image on the anode target is effected by a magnetic coil 28<SP>1</SP> carried on brackets inwardly directed from the housing 1 surrounding the X-ray tube 15. The X-ray tube is releasably secured by screwing in a cradle 16 forming part of the driving shaft 11 connected to an electric motor 12 by an insulated coupling 14. The space surrounding the motor 12 and coupling 14 may be filled with insulating liquid or gas, passage of which through the bearing 8 may be prevented by gland means 8a. The electric motor coils 17 and the magnetic core 17<SP>1</SP> of an electric generator for heating the cathode filament 20 are mounted on the tubular end of the rotating cradle 16. The annular fixed magnetic core 18<SP>1</SP> of the generator is mounted on the wall of the housing 1, the winding 18 being carried on salient field poles 18<SP>11</SP> extending radially inwardly from the core 18<SP>1</SP>. A magnetic shield 28<SP>11</SP> prevents the field of the filament generator influencing the cathode beam. Windows 40 in the tube 15, the cradle 16 and the housing 1 are provided for the X-rays. The coil 28 for positioning the beam on the anode can be replaced by two iron-cored or coreless coils or permanent magnets providing magnetic fields of the same polarity, but preferably individually variable intensity, acting along an axis at right angles to the axis of rotation of the electrodes. A third coil may be arranged to provide a magnetic field acting along an axis substantially at right angles to the axis of rotation and to the axis of the fields of the first two coils.