Depth dose determination for a mixed radiation field using a thin plastic scintillator dosimetry system

Plastic scintillators, due to their favorable characteristics compared with other dosimetry techniques, were used as detectors to estimate dose distributions in high gradient dose fields. In this study, a thin plastic scintillator (type BC-408) was coupled to a photomultiplier tube and multichannel analyzer as a technique for real-time dose measurements. The well-defined beta, gamma, and beta-gamma emitters (137Cs, 133Ba, 22Na, 109Cd, 55Fe, and 241Am) have enabled parallel depth dose measurements with Monte-Carlo calculations to be critically compared. The measurements of doses were made for depths range of 0.1 mm to 5 mm. The MCNP dose results were comparable with the plastic scintillator detector and can be used to approximately estimate the dose rate values from mixed electron-photon fields. The minimum dose rate that can be measured by the plastic scintillator system was ∼2 μGy/h and was for 109Cd source of activity 222 Bq. (author)