Comparison of measured and Monte Carlo-calculated electron depth dose distributions in aluminium

Abstract

Depth dose profiles in aluminium have been measured using the cellulose triacetate dosimeter against different electron energies (4, 4.5 and 5 MeV) at a recently upgraded 15 kW industrial electron beam accelerator facility. The study also includes comparison of these profiles against Monte Carlo calculations. The measured and simulated depth dose profiles are similar in shape. For all electron energies, at initial depths, the measured doses are higher than the simulated ones. The simulated and measured normalized surface dose values are 0.58 and 0.66, respectively, independent of electron energy. The difference in the surface dose between Monte Carlo and experiment could be attributed to possible presence of low energy electrons in the measurements whereas the Monte Carlo calculations are based on monoenergetic electrons. Between the region of dose maximum and the tail portion of the depth dose curve, the measured dose is smaller than the simulated values (about 17% to 40% at 5 MeV). Using the depth dose profiles, electron beam parameters such as depth at which maximum dose occurs, d_max, practical range, R_p and half-value depth, R₅₀ have been determined. Using the measured parameters R_p and R₅₀, the incident kinetic energy of the electron beam has been determined. The estimated electron energies while using R_p are 4.02, 4.41 and 4.75 MeV. When using R₅₀, the corresponding values are 3.83, 4.21 and 4.64 MeV. The measured R_P/R₅₀ ratios are slightly larger than the Monte Carlo-calculated values, which suggest that the electron beam may not be monoenergetic.