First demonstration of a novel single-end readout type position-sensitive optical fiber radiation sensor based on wavelength-resolved photon counting

In this study, a single-end readout type position-sensitive optical fiber radiation sensor was developed. Using the wavelength dependency of light attenuation inside the optical fiber, the incident position of radiation at the fiber can be estimated reversely. Instead of a spectrometer, we employed bandpass filters and photon-counting head as a photodetector to improve detection efficiency. The detection efficiency of a 10 m long plastic scintillation fiber at the 5 m position from the readout end was evaluated to be in the range of 0.08–0.12 % for 662 keV gamma-rays from ¹³⁷Cs and 2.6–3.9 % for beta-rays from ⁹⁰Sr/⁹⁰Y when a bandpass filter transmitting photons with a wavelength of 500 nm was used. A basic measurement test of radiation intensity distribution was conducted using a ⁹⁰Sr/⁹⁰Y radioactive point source. A field test was also performed at the difficult-to-return zone in Fukushima Prefecture, and the estimated dose rate distribution roughly agreed with the survey meter measurement.