GafChromic MD‐55: Investigated as a precision dosimeter

GafChromic MD‐55 is a fairly new, thin film dosimeter that develops a blue color when irradiated with ionizing radiation. The increase in absorbance is roughly proportional to the absorbed dose. In this study, GafChromic MD‐55 was irradiated with γ rays. A double irradiation method was used in which a dosimeter is given an unknown dose followed by a known, calibration dose. With this method, GafChromic MD‐55 was used to measure doses in the vicinity of 6 Gy with an uncertainty of less than 1%. It was found that the measured optical density of GafChromic MD‐55, as presently fabricated, is affected by the polarization of the analyzing light, an important consideration when using GafChromic MD‐55 as a precision dosimeter. GafChromic MD‐55 was found to consist of seven layers. The response to polarized light was measured for the whole dosimeter and for the three Mylar films which form part of the dosimeter.