The Emission and Transmission of X and Gamma Radiation

A survey of the published data from the N.P.L. and some sixteen other research centres in this country and abroad, on the rates of X-ray emission from X-ray generators of nine different types operating at voltages from 200 kV to 2,000 kV, shows that the X-ray output of a tube in rontgens (r) is predictable at any practicable voltage under standard conditions of operation, whether for “reflection” or “transmission” X-ray targets. It further appears that the maximum X-ray output from a present-day 2-million volt tube is comparable with the gamma-ray output from about 16,000 grammes of radium. The paper next deals with a method of calculating the progressive X-ray absorption by materials, based on Kramers' formula for X-ray emission and a graphical method of solution, utilising theoretical data for the components of the absorption coefficients of a “narrow” beam of X rays, at a series of selected wavelengths in the continuous spectrum. The derived transmission curves for different exciting voltages are illus...