Development and Comparison of Fiber-Optic Beta Radiation Sensors with Different Diameters of Their Sensing Probes

A fiber-optic radiation sensor (FORS) was developed for remote and real-time measurements of beta radiation from radioactive-contaminated soil. The sensing probe consisted of a bundle of organic scintillators and a mixture of epoxy resin to improve the detection efficiency. The measurement system consisted of a sensing probe with an aluminium foil reflector, a transmitting plastic optical fiber, and a light-measuring system comprising a photomultiplier tube, a preamplifier, a multichannel analyzer, and a laptop computer. Several sensing probes, whose dead-end diameters were 26 mm (bundle type I), 36 mm (bundle type II), and 46 mm (bundle type III), were prepared and characterized to identify the best sensing probe in terms of its radiation detection efficiency. The reproducibility of the FORS for the measurement of beta radiation was confirmed using a χ²-test. The measurements showed that the FORS sensing probe with a diameter 46 mm has the best detection performance.