The “Quality” of an X-ray Tube and How to Measure It

Abstract

IN earlier papers the writer has described some investigations on the temperature rise of the anode of an X-ray tube and its load-carrying capacity and on the size and shape of the focal spot.1 Some of the conclusions are: 1. An anode of copper provided with a thin tungsten target may carry a load of 200 watts per sq. mm. for one second. A much larger load would result in too high a temperature and consequently in evaporation or melting of tungsten or copper. 2. The best type of focus is the line focus, with the X-ray beam at an angle of about 20° to the surface. Such a line focus carries a load which is one and a half to two times larger than that carried by a circular focus of equal area. 3. The size of the focal area is far less important than the type of focus and its load-carrying capacity per unit area or “specific capacity.” For a given sharpness of definition, a large focus requires a longer distance, and, as the energy required for a given exposure time and the area of the focal spot are both pro...