Voltage, energy, and material dependence of secondary radiation

Measurement results of the relative contribution of primary and secondary radiation are presented. Measurements were done with both monoenergetic and broad spectrum x-ray beams. A variety of phantoms were used: graphite, water, lucite, a skull phantom, and aluminum. We found that the primary radiation fraction is nearly independent of photon energy and tube potential. Calculations using a simple single Compton scattering model agree with the experiment results.