Towards improving the detection limit of electron paramagnetic resonance (EPR) dosimetry of drywall (wallboard)

The intensity of the electron paramagnetic resonance (EPR) line corresponding to the carbonate free radical (CO3-) in gypsum (CaSO4·2H2O) drywall was previously shown to be proportional to absorbed dose. Heating irradiated drywall reduces the radiosensitive signal of the CO3- radical. The response of the CO3- EPR line to heat treatments is being studied in order to determine a background for an arbitrary drywall sample. Ultimately this is expected to improve the precision of dose measurements with drywall and to reduce the detection limit. Controlled heating of irradiated drywall was performed at temperatures between 50oC and 100oC. Although higher temperatures reduce the radiosensitive signal rapidly, the non-radiosensitive EPR signals are affected dramatically as well, presumably due to a phrase change from gypsum to plaster of Paris to anhydrite.