The X-ray and Gamma-ray Protective Values of Building Materials

Abstract

Measurements of the lead equivalents of various building materials which may be used in providing protection for X-ray and radium workers have been made for X rays excited at voltages up to 400 K.V. and for radium gamma rays. The protective values increase with exciting voltage, reaching a maximum at about 100 K.V., then fall to a minimum at about 200 K.V. and subsequently rise continuously. Protective values for X rays excited at voltages up to 5,000 K.V. and for radium gamma rays, have also been deduced, using theoretical and practical data relating to the energy distribution in X-ray and gamma-ray spectra and to the photoelectric, scattering, and nuclear absorption processes. The satisfactory agreement between the experimental and computed values for X rays excited at voltages between 200 and 400 K.V. and for radium gamma rays suggests that the method can be applied to estimate the lead equivalent of a material at any voltage with an accuracy which is probably adequate for medical requirements.