A useful formula for the radiological calibration laboratory

A useful technique for determining the relationships between irradiation position and air kerma or neutron dose equivalent rate is presented. The standard geometric model (1/r2) is expanded allowing the user to include curvature in the model caused by scattered radiation. This technique applies to clean irradiation geometries that are well modeled by the standard geometric model, high-scatter geometries encountered in well irradiators, and neutron irradiation fields used to calibrate health physics instruments and personnel dosimeters. The technique, with slight modification, is also useful for determining the quality of x-ray beams. The basic equations and the implementing Excel functions are listed. In addition, several examples are presented to demonstrate the application of the technique.