Absorbed Dose Determination for X-rays in the Grenz-ray Region (5 to 20 keV Quantum Energy)

Abstract

Determination of absorbed dose for very low-energy X-rays is greatly simplified since there is no scattered radiation. Absorber thickness can be scaled from one material to another by use of a relative effective density, i.e., the ratio of the mass energy absorption coefficients. Depth dose functions can be transferred from one material to another and from one FSD to another, and can be corrected for changes in air absorption. Exposure in roentgens can be measured directly with a suitable extrapolation chamber. The Fricke ferrous sulphate dosemeter is readily applicable, and a value of G = 14.8 was found for a 50 kvp unfiltered X-ray beam from a beryllium-window tube. The properties of very low-energy X-rays do not necessarily add to the uncertainties inherent in all X-ray absorbed-dose determinations.