Broad-and Narrow-Beam Attenuation of 500- to 1,400- Kilovolt X-Rays in Lead and Concrete

There have been numerous papers over the past 10 years dealing with X-ray protection in the range from 500 to 2,000 kv [1 to 6]. The data from these papers differ somewhat, because the conditions of the experiments were not always the same and therefore cannot be readily correlated. Part of this has been attributed to differences in the high-voltage wave form and inherent filtration for the several experimental arrangements used. Preliminary data [1 to 6] have indicated that the size of the irradiated area of the barrier may also be an important variable, but the magnitude and limits for this have not been explored quantitatively. The present report will deal with different sized beams of X-rays produced by direct-current potentials of 500, 600, 800, 1,000, and 1,400 kv with a transmission target. Barriers of lead and concrete will be considered. Concrete has been generally accepted in the energy range above about 500 kv where space is not important, because it is structurally self-supporting and relatively inexpensive. However, for applications requiring a minimum of thickness for a given protection, lead is still the most popular. In the voltage range under consideration, X-rays are principally absorbed by the photoelectric and the Compton processes, since pair production is still relatively unimportant, even in lead for 1,400 kv. All of the photoelectric