Application of egs4 computer code for determination of gamma ray spectrum and dose rate distribution in gammacell 220

The EGS4 a Monte Carlo electron-photon transport simulation package together with a locally developed computer program “GCELL” has been used to simulate the transport of the gamma rays in Gammacell 220. An additional lead attenuator has been inserted in the chamber, has been included for those cases where lower dose rates were required.

For three cases of 0, 1.35 and 4.0 cm thickness of added lead attenuators, the gamma spectrum, and dose rate distribution inside the chamber have been determined. For the case of no attenuator present, the main shield around the source cage has been included in the simulation program and its albedo effects have been investigated.

The calculated dose rate distribution in the Gammacell chamber has been compared against measurements carried out with Fricke, PMMA and Gafchromic film dosimeters.