Measuring solar UV radiation with EBT radiochromic film

Abstract

Ultraviolet radiation dosimetry has been performed with the use of a radiochromic film dosimeter called Gafchromic EBT for solar radiation exposure. The film changes from a clear colour to blue colour when exposed to ultraviolet radiation and results have shown that the colour change is reproducible within ±10% at 5 kJ m(-2) UV exposure under various conditions of solar radiation. Parameters tested included changes in season (summer versus winter exposure), time of day, as well as sky conditions such as cloudy skies versus clear skies. As the radiochromic films' permanent colour change occurs in the visible wavelengths the film can be analysed with a desktop scanner with the most sensitive channel for analysis being the red component of the signal. Results showed that an exposure of 5 kJ m(-2) (approximately 1 h exposure in full sun during summer) produced an approximate 0.28 change in the net OD when analysed in reflection mode on the desktop scanner which is significant darkening. The main advantages of this film type, and thus the new EBT2 film which has replaced EBT for measurement of UV exposure, is the visible colour change and thus easy analysis using a desktop scanner, its uniformity in response and its robust physical strength for use in outside exposure situations.

Correction of nonuniformity error of Gafchromic EBT2 and EBT3

“…Because the active layer of a Gafchromic film reacts to UV rays, 17 , 18 UV irradiation is effective only if appropriately applied. For instance, UV irradiation can markedly improve the uniformity of Gafchromic EBT (16) .…”

Modeling Coloration of a Radiochromic Film with Molecular Dynamics-Coupled Finite Element Method

“…The attraction forces among the DA monomers were governed by attraction forces among atoms in the chains, which were inversely proportional to separations among the atoms. The simulation box consisted of~10 6 (carbon + hydrogen) atoms in total, which accounted for~15,000 DA monomer strands. A section of the simulation box is shown schematically in Figure 1.…”

“…Application of radiochromic films for clinical X-ray dosimetry has, in essence, relied on dose-response curves (response in terms of film coloration) obtained through calibration. However, many intriguing properties of radiochromic films are not yet fully understood, including their responses to fluorescent light [3,4] and ultraviolet (UV) radiation [5][6][7][8]; the energy dependence of their responses [9][10][11][12][13]; the effects of polarization and scanning orientation [14][15][16]; and the effects of mechanical pressure [17] and auto-development [18], etc. In order to understand these intriguing properties, development of a theoretical model at both atomic and macroscopic scales is pertinent.…”

Comparing three UV wavelengths for pre‐exposing Gafchromic EBT2 and EBT3 films

“…However, it is difficult to provide homogenous X‐ray exposure over a wide area, such as a $14\times 17$ inch format. It is known that Gafchromic films react with certain ultraviolet (UV) rays (4) . Gafchromic films have been used to measure the amount of UV rays using this reaction (5) .…”