Dye Film Dosimetry for Radiation Processing

Commercially available plastic films containing dyes or dye precursors are convenient dosimeters and imaging media for electron beams or photons used for industrial radiation processing. As "grainless" imaging systems having thicknesses down to a few micrometers, they provide high spatial resolution for determining detailed absorbed dose distributions through microdensitometric analysis. The radiation absorption properties of these systems are adjusted by changing film composition so that the dosimeter materials can be made to simulate the material of interest undergoing irradiation (e.g., tissue, bone, various insulating materials, semiconductor devices, and a wide assortment of polymers). Other advantages include long-term stability, dose-rate independence, and ease of use and calibration. Radiochromic dye films with thicknesses varying from 0.005 to 1 mm are presently used to monitor electron-beam or gamma-ray doses from 10 to 105, Gy (103 to 107 rad), typical of those encountered in medical applications, radiation curing of polymeric composites, wire and cable insulation, shrinkable plastic tubing and film, as well as sterilization of medical supplies and treatment of municipal and industrial wastes. An NBS calibration service to industry involves the traceability of standard 60Co gamma ray absorbed dose measurements by means of these films employed as transfer standards.