Ionizing radiation detectors based on Ge-doped optical fibers inserted in resonant cavities.

Roberto Pacelli,Gianluca Gagliardi,Vittoria D'Avino,Paolo De Natale,Antonio Giorgini,Saverio Avino,Laura Cella,Raffaele Liuzzi

doi:10.3390/s150204242

Roberto Pacelli, Gianluca Gagliardi + Show 6 more

Open Access

https://doi.org/10.3390/s150204242

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Abstract

The measurement of ionizing radiation (IR) is a crucial issue in different areas of interest, from environmental safety and industrial monitoring to aerospace and medicine. Optical fiber sensors have recently proven good candidates as radiation dosimeters. Here we investigate the effect of IR on germanosilicate optical fibers. A piece of Ge-doped fiber enclosed between two fiber Bragg gratings (FBGs) is irradiated with gamma radiation generated by a 6 MV medical linear accelerator. With respect to other FBG-based IR dosimeters, here the sensor is only the bare fiber without any special internal structure. A near infrared laser is frequency locked to the cavity modes for high resolution measurement of radiation induced effects on the fiber optical parameters. In particular, we observe a variation of the fiber thermo-optic response with the radiation dose delivered, as expected from the interaction with Ge defect centers, and demonstrate a detection limit of 360 mGy. This method can have an impact in those contexts where low radiation doses have to be measured both in small volumes or over large areas, such as radiation therapy and radiation protection, while bare optical fibers are cheap and disposable.

Highlights

In the last decades, there has been a growing need for detection and quantification of ionizing radiation (IR) in different contexts, such as environmental safety, industrial processes monitoring, radiation protection and medicine
The detection method relies on the measurement of the thermo-optic response variation of a short length of Ge-doped optical fiber after exposure to IR
We investigated the effects of IR on standard SMF28TM Ge-doped fibers

Summary

Introduction

There has been a growing need for detection and quantification of IR in different contexts, such as environmental safety, industrial processes monitoring, radiation protection and medicine. Like solid state detectors, combine a very small volume with a relatively high response, but further studies on the underlying theories for recombination effects are still needed for them to become a feasible option. Optical fiber sensors can be multiplexed so that a single reading unit can control several sensors Thanks to their mechanical nature and very small size, fibers lend themselves to the realization of miniature radiation detectors with different geometries without perturbing the dose measurement. The effects of ionizing radiation have been found to be sufficient to induce losses much greater than intrinsic fiber loss (~dB/km) from the visible to the near-infrared spectral range, even at low/moderate doses (in the range 1–10 Gy) [18,19,20] In all these cases, the interaction with IR can be quantified by measurements of the transmitted light intensity.

Phenomenology and Structural Models of Radio-Induced Point Defects in

Experimental Section and Results

Conclusions