Spectral response of radiochromic gel detector in the near-ultraviolet region (200–400 nm)

• Spectral response of FXG gel material at monochromatic wavelengths in the near ultraviolet spectrum was investigate.
• Changes in optical absorbance at 560 nm were considered as indicator for FXG gel detector response to ultraviolet radiation.
• The influence of optical path on FXG response was studied.
• FXG gel detector response in near ultraviolet spectra is related to the gel thickness and the exposure radiation wavelength.

Tissue-equivalent radiochromic gel detector is sensitive in the regions of ultraviolet radiation (UVR) and gamma and X-rays. This study aims to investigate the spectral response and other optical properties of the ferrous sulphate, xylenol orange and gelatin (FXG) radiochromic gel dosimeter at particular UVR wavelengths. A total of nine monochromatic wavelengths were selected in the range of 240–400 nm with an increment of 20 nm. The FXG spectral response was estimated from the variation of spectral absorbance at 560 nm resulting from 1 h exposure to UVR beam at each chosen wavelength. Experimental results show that the FXG responsivity depends on the wavelength of the radiation and the optical path in the gel material. UVC and UVB photons have relatively higher photochemical effect than UVA; however, UVA penetration is deeper. Investigations showed that the FXG gel response is relatively constant between 240 and 320 nm, but it varies rapidly with wavelength in the UVA range and takes a minimal value at 360 nm. UVR spectral absorbance curves for different gel sample thicknesses were examined. The experiment showed that 6 mm of neutral gelatin or FXG gel samples was capable of absorbing >99.7% of the beam in the UV range of 240–290 nm.