Effect of Gafchromic™ EBT2 radiochromic film's components on the detection of UVA solar radiation selectively

Abstract

The response of Gafchromic™ EBT2 film selectively to UVA solar radiation was studied. A set of EBT2 films was exposed from the topside (80 μm) and the other set from the polyester substrate (175 μm) for different durations. The EBT2 topside components absorb wavelengths shorter than 400 nm, while the polyester substrate absorbs wavelengths shorter than 315 nm. Accordingly, EBT2 film can detect solar UVA radiation (315–400 nm) by calculating the difference (net change) between the irradiated sets. For EBT2 film exposed from polyester substrate, the red, green and grey color channels are decay exponentially with exposure time, where the green color channel has the highest sensitivity. When EBT2 film is exposed from the topside, red, green and grey color channels are linearly correlated with exposure time, but showing poor sensitivity. For EBT2 exposed from topside, the absorbance peaks at 580 ± 2 nm and 632 ± 2 nm are slightly increasing with the increase in the exposure time, while for EBT2 films exposed from polyester substrate; the characteristic peaks are correlated exponentially with exposure time and saturated after 80 min. The net effect of solar ultraviolet UVA radiation on EBT2 films increases exponentially with exposure time with tendency to saturate at prolonged exposure. It is found that the EBT2 films digitization with flatbed scanner has a higher sensitivity but a narrower dynamic range, while analysis with UV–Vis spectrophotometer has lower sensitivity but a wider dynamic range. This new findings pave the way to measure UVA radiation (315–400 nm) using a simple equipment including Gafchromic™ EBT2 film and flatbed scanner.