Reflection spectrometry analysis of irradiated GAFCHROMIC XR type R radiochromic films.

The absorption spectra of the GAFCHROMIC XR type R radiochromic film measured with reflectance spectroscopy have been investigated in order to analyze the dosimetry characteristics of the film. Like the XR type T film, this film features two peaks in its absorption spectrum, approximately at 676 and 618 nm, whose intensities increase with increasing absorbed dose. When the main absorption peak at 676 nm is used, the XR GAFCHROMIC type R film is approximately 1.4 times more sensitive to radiation doses in the 0-5 Gy range than the XR type T film. The major difference of the films of this type from the original GAFCHROMIC film products is the opaque backing material, which permits only reflected, but not transmitted, light measurements as a means of analysis. A yellow dye is used as the opaque backing to enhance the visible color change for qualitative assessment of the delivered dose. The XR type R radiochromic film in combination with reflection spectroscopy can provide accurate assessment of doses.