Experimental Verification of Non-Equilibrated Bremsstrahlung Dosimetry Predictions for 0.75 MeV Electrons

Absolute Monte Carlo predictions of the combined x-ray production and energy deposition in low-Z (Al) and high-Z (Ta) encapsulated thermoluminescent dosimeters for a 0.75-MeV electron/bremsstrahlung source have been experimentally verified over a large range of encapsulation thicknesses and conditions. The effect of the Al is primarily manifested by an alteration in the x-ray flux reaching the active CaF2 material in the dosimeter. For Ta encapsulation, however, there is clear evidence of high-Z/low-Z interface phenomena, where both fluorescence and photoelectrons from the Ta make significant contributions to enhanced energy deposition in the CaF2. During the experiment, this interface enhancement-factor for the encapsulation relative to Al encapsulation was measured directly. The good agreement between the absolute predictions and measurements reported here represents an important verification of the Monte Carlo model for predicting integral interface phenomena.