Radiometric characterization of radiochromic gel material applied for UVA radiation dosimetry

Diverse kinds of chemical products are useful for UVA dosimetry due to chemical incitation properties of ultraviolet radiation. It was recognized and approved that radiochromic gel materials have a specific behavior under UVA radiation exposure. The relationship between the UVA dose and the variation of visible light absorbance was found to follow a second-order function with good accuracy. Specific metrological properties of the gel material for radiometric UVA dosimetry application were studied at irradiation levels simulate deferent natural solar UVA radiation levels. The behavior of the gel absorbance properties, detector linearity, induced reaction and temporal and radiometric stability at various dose rate levels were investigated. The relationship between UVA dose and changes in optical absorbance is found independent of the UVA exposure rate including the solar UVA maximum level which could be detected at sea level. The studied gel material absorbs more than 90% of UVA radiation in 1 cm of the gel thickness. Gel detector linearity was investigated over a UVA range (20-84 W/m²) which exceeds the natural solar UVA radiation level and the linearity factor was found to be close to 1 with statistical differences ≤ 2%. The UVA induced dark reaction in the gel material continues for almost 4 min after stopping irradiation; which must be considered during measurements. The detector has good temporal stability even under high UVA exposure; hence the gel absorption in the UVA spectrum region is stable. Measured deviation was less than 1%, and relative variation of gel optical absorbance in UVA spectrum is about 35 times lower than that occur in visible region.