GB560815A - Improvements in and relating to methods of conditioning anodes for x-ray generating apparatus - Google Patents

Abstract

560,815. Rontgen-ray tubes. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.) June 4, 1942, No. 7636. [Class 39 (i)] [Also in Groups II and XXXVI] The anode of an X-ray tube is made resistant to cracking by first polishing it and then subjecting it to an aging process by progressively increasing its temperature to promote slow crystallization of the anode material. The polishing is preferably performed by an electrolytic process in a bath of sodium hydroxide and sodium carbonate. Full details of temperature, concentration and current density are given. An oxide coating is produced which is removed by immersing the anode in hydrochloric acid. The aging process consists in subjecting the anode when mounted in the tube to a series of electron bombardments, starting at one half of the rated capacity and finishing at a load in excess of the operating load, periods of rest being allowed between each bombardment. Full details of times and loads are given. At the same time occluded gases are removed from other parts of the tube. As part of the conditioning of the tube, a gettering process may be carried out before or during, but preferably after, the aging process. To prevent deposition of gettering material upon the electrodes, it is contained in a nearly closed pocket within either the anode or the cathode. In one form the anode F, Fig. 3, has a dependent skirt which surrounds the bearings 37, which in turn are supported from a cup-shaped member 27 sealed to the glass stem R. The gettering wire 19 is mounted between the bearings and is heated by an independent lead 30. In this form the gettering material is also deposited upon the bearings 37 and serves as a lubricant therefor. The anode is rotated during this process. In another form the cathode C, Fig. 6, has a depending skirt 55 which contains the gettering wire 19 supported on the central, post 26 within which passes the independent heating lead 30. Two filaments 49 are provided. The gettering wire comprises a tube 19, Fig. 8, containing the gettering material 33 and flattened at one side 21 so as to present a thin wall portion through which the material evaporates on heating. Sufficient getter material may be left to enable reconditioning of the apparatus to be carried out during its working life. Specifications 411,503 and 542,665, [Group II], are referred to.