Atmospheric Neutron Monitoring through Optical Fiber-Based Sensing

Abstract

The potential of fiber-based sensors to monitor the fluence of atmospheric neutrons is evaluated through accelerated tests at the TRIUMF Neutron Facility (TNF) (BC, Canada), offering a flux approximatively 109 higher than the reference spectrum observed under standard conditions in New York City, USA. The radiation-induced attenuation (RIA) at 1625 nm of a phosphorus-doped radiation sensitive optical fiber is shown to linearly increase with neutron fluence, allowing an in situ and easy monitoring of the neutron flux and fluence at this facility. Furthermore, our experiments show that the fiber response remains sensitive to the ionization processes, at least up to a fluence of 7.1 × 1011 n cm−², as its radiation sensitivity coefficient (~3.36 dB km−1 Gy−1) under neutron exposure remains very similar to the one measured under X-rays (~3.8 dB km−1 Gy−1) at the same wavelength. The presented results open the way to the development of a point-like or even a distributed dosimeter for natural or man-made neutron-rich environments. The feasibility to measure the dose caused by the neutron exposure during stratospheric balloon experiments, or during outer space missions, is presented as a case study of a potential future application.

Extreme Radiation Sensitivity of Ultra-Low Loss Pure-Silica-Core Optical Fibers at Low Dose Levels and Infrared Wavelengths

“…From the existing literature, one could assume a good fiber radiation resistance in the IR part of the spectrum compared to other classes of optical fibers. The Ge-doped ones are usually notably quite sensitive to radiation [ 4 ] and the phosphosilicate ones are known to be so highly radiation sensitive that they are today used for distributed dose monitoring (i.e., at CERN, the European Organization for Nuclear Research, or in neutron-rich environments) [ 6 , 7 ]. The RIA, indeed, depends on the fiber composition, but also on other parameters such as the fiber treatment (i.e., a pre-loading with H 2 , the irradiation conditions such as particle type, dose, dose-rate, irradiation temperature), and the injected light power, which can bleach radiation-induced point defects [ 5 ].…”

Radiation Effects on Fiber Bragg Gratings: Vulnerability and Hardening Studies

“…Consequently, the RIA is mainly independent of the radiation nature [ 38 ] for most of the targeted environments (except for, e.g., nuclear core instrumentation). For example, the P1 is a center induced in the P-doped silica, absorbing around 1.5 µm: the growth kinetics of its absorption band is independent of the nature of irradiation, i.e., γ- or X-rays, protons, and neutrons, which makes it, together with other properties, a very good dosimeter of total ionizing dose in mixed environments [ 61 , 69 , 107 ].…”

A novel fiber-optic beam monitor

“…Organic and inorganic Optical Fibers (OFs) are increasingly utilized in space and medical applications, including accelerator and reactor environments to monitor beam currents and shapes, doses, temperatures, and pressures [8,9,10,11,12]. OFs are ideal as they can be radiation hard, small in size, independent from electromagnetic environments, and linear over a large measurement range.…”