MEASUREMENT OF P-REPL P-WALL FACTORS IN ELECTRON-BEAMS AND IN A CO-60BEAM FOR PLANE-PARALLEL CHAMBERS

This paper describes a method to measure the product of PreplPwall cor rection factors for ionization chambers and presents our measured valu es of PreplPwall for Markus plane-parallel chambers in electron beams. It is shown that the measured values of PreplPwall can be fitted to a n equation, PreplPwall = c(1) + c(2)R(50) + c(3)(R-50)(2), for Markus chambers at the new reference depth for electron beams (6 MeV less tha n or equal to nominal energy E less than or equal to 20 MeV). We also present our measured values of PreplPwall for NACP and Markus chambers in a water phantom irradiated in a Co-60 beam. (C) 1998 American Asso ciation of Physicists in Medicine.