A Filament Changing Device for Continuously Evacuated X-ray Tubes

Abstract

In continuously evacuated dismountable X-ray tubes the cathode filament is usually renewed by removing the filament conductor assembly from the tube and replacing the filament holder with a spare holder in which a new filament has already been mounted. This necessitates the breaking of the vacuum and subsequent re-evacuation of the X-ray tube, a process which may take an hour or so to complete in the case of the 200–250 K.V. tubes used for deep X-ray therapy. Very large continuously evacuated X-ray tubes such as, for example, the 1,000 K.V. tube installed in the Mozelle Sassoon High Voltage X-ray Therapy Department at St. Bartholomew's Hospital, in London, are not so easily re-filamented as the smaller tubes, first because of the greater difficulty in removing the filament conductor assembly from the tube and secondly because of the longer time taken to break the vacuum and afterwards re-evacuate the tube. In order to reduce, as far as possible, the number of occasions on which the large X-ray tube would ...