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Description
Gamma ray spectroscopy represents a fundamental instrument for the characterisation of gamma radiation and the identification of its sources. The most common approach is the utilisation of scintillator detectors. In this method, the photodetectors are situated in direct contact with the scintillator and are frequently also subjected to gamma radiation. To enhance the stability and reliability of the monitoring process, an optical fibre could be positioned between the two, effectively conveying the signal from the irradiated area to photosensitive electronic components situated in a location that remains outside of the radiation field. Consequently, this eliminates the need for direct exposure of personnel to radiation, thus ensuring safety while facilitating long-term, high-activity, and high-energy monitoring. The measurement is linear in trend and variable with the utilisation of disparate scintillator materials and shapes. Nevertheless, the introduction of optical fibres between the scintillator and the photosensitive equipment presents certain challenges, most notably a reduction in the capacity to recognize gamma spectra. The observed signal degradation is primarily attributed to the diameter of the fibre and several phenomena, including modal and chromatic dispersion, which limit light transmission and ultimately yield a distorted signal. Although plastic fibres with larger diameters and correspondingly sized scintillators are capable of transmitting spectra over relatively short distances, their vulnerability to high-energy radiation significantly limits their applicability in the field of research. In order to address this issue, the optical fibre link was replaced with an adjustable iris, which permits precise regulation of the aperture diameter. This modification enables the simulation and assessment of the fibre's spectral transmission properties. By means of a systematic modification of the iris, the influence of aperture size, and consequently the impact of optical fibre diameter on signal transmission, is addressed. This process allows for the identification of the optimal diameter for the optical link and the determination of the threshold beyond which reliable spectral recognition becomes unattainable. The methodology provides valuable insights into the improvement of spectral clarity and represents the initial step toward effective spectral transmission through silica optical fibres from scintillators. This ensures the reliable identification of ionising radiation sources over longer distances, even in challenging environments characterised by high radiation activity.
