Design and construction of a new optical depth-dose reader for electron beam energy measurement

Dose-depth analysis is a usual method for measuring electron beam energy of accelerator. The aim of this study is to design and construct an optical scanner with the ability of depth-dose curve drawing of electron beam and measurement of mean electron beam energy. In the present research, a microscope slide is used instead of dosimeter film in the aluminum wedge and the depth-dose distribution in the slide is extracted by our home-made scanner instead of spectrophotometer. Electron beam irradiation led to color change in the slide, and the optical absorption coefficient changed proportional with dose. The slide was irradiated by electron beam of Rhodotron TT200 accelerator with initial dose of 14.5 kGy. An optical reader including a stable power (3W) LED source with 520–560 nm wave lengths, accompanied by a TCS3200 detector with 0.1 mm precision were used. Our results showed the electron beam maximum energy produced by Rhodotron was 9.79 ± 0.017 MeV, which was similar to the result of other studies. The results also showed that the color points in irradiated slide faded gradually, but depth-dose curve remained unchanged up to 157 days so this color fading did not cause error in the electron beam energy measurement. The energy measurement precision error in this method was 0.17% and our different results compared to standard method results for average electron energy during various times were 0.03 MeV to 0.3 MeV.