Optical Radiation Sensors Research Articles

First demonstration of a single-end readout position-sensitive optical fiber radiation sensor inside the Fukushima Daiichi Nuclear Power Station based on wavelength-resolving analysis

We have developed a new position-sensitive optical fiber radiation sensor that achieves single-end readout and high dose rate application. The sensor determines the incident position of radiation on the optical fiber by using the wavelength dependence of light attenuation within the fiber. Through analysis of the wavelength spectrum output from the fiber end, the incident position of radiation on the optical fiber can be inversely estimated via spectrum unfolding. Using this optical fiber sensor, we measured the radiation distribution inside the Fukushima Daiichi Nuclear Power Station (FDNPS). The actual trend of the incident position of radiation was successfully reproduced in a high dose rate area, with the maximum dose rate exceeding 100 mSv/h. This validates the effectiveness of our new position-sensitive optical fiber radiation sensor.

Radiation Induced Attenuation and Luminescence Study in Radioluminescent Optical Fibers

We present experimental characterization of both RIA (Radiation Induced Attenuation) and RL (Radioluminescence) of differently doped optical fibre radiation sensors. We present data for different sample lengths and Total Ionizing Dose (TID) up to 600 kGy (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) under X-rays. Combined RIA and RL responses are used to attempt explaining the variation of the RL signal with TID on those fibres.

Characterization of a Fiber Optic Radiation Sensor Prototype for Nuclear Dismantling

The use of an active measurement system to localize contamination in concrete structures of nuclear facilities offers advantages such as an easy on-site analysis within a short measurement time. A measuring system based on a scintillation crystal connected to a long optical fiber with a large diameter could satisfy the demands of a measuring system for gamma-ray spectroscopy in boreholes. This work describes the development of a gamma-ray spectroscopy system using a fiber optic radiation sensor. A prototype was built with a GAGG scintillation crystal, which could reach an energy resolution of 33% at the 662-keV gamma-ray emission energy of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs. A minimal time for the detection of a contamination of a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs source with an activity of 21 kBq and a layer of 6-cm concrete between sensor and radiation source was determined to be under 1 min with three different evaluation methods. They were based on the decision threshold and the Kolmogorov–Smirnov test corresponding to the energy distribution and the distribution of time differences between detector events. In addition, it was possible to estimate the distance of a point-like source from the sensor by establishing a further analysis parameter comparing different energy regions of a spectrum.

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.

Recent Advances in Optical Fiber Enabled Radiation Sensors.

Optical fibers are being widely utilized as radiation sensors and dosimeters. Benefiting from the rapidly growing optical fiber manufacturing and material engineering, advanced optical fibers have evolved significantly by using functional structures and materials, promoting their detection accuracy and usage scenarios as radiation sensors. This paper summarizes the current development of optical fiber-based radiation sensors. The sensing principles of both extrinsic and intrinsic optical fiber radiation sensors, including radiation-induced attenuation (RIA), radiation-induced luminescence (RIL), and fiber grating wavelength shifting (RI-GWS), were analyzed. The relevant advanced fiber materials and structures, including silica glass, doped silica glasses, polymers, fluorescent and scintillator materials, were also categorized and summarized based on their characteristics. The fabrication methods of intrinsic all-fiber radiation sensors were introduced, as well. Moreover, the applicable scenarios from medical dosimetry to industrial environmental monitoring were discussed. In the end, both challenges and perspectives of fiber-based radiation sensors and fiber-shaped radiation dosimeters were presented.

Nitrogen determination in irrigated rice using spectral reflectance

AbstractPrecision N management using optical radiation sensors is a promising management strategy. Using a combination of three spectral reflectance bands, 22 vegetation indices (VIs) were calculated and evaluated for their efficiency in estimating N status in irrigated rice (Oryza sativa L.) during growth stages. The results obtained here have showed a promising strategy to include crop stages as covariate in generalist models to predict the N status parameters for irrigated rice. This approach is interesting because it reduces the need for specific models, with different structures, for each crop stage. In addition, including crop stages as a covariate in the prediction models allows knowing the rice N status according to the crop stage, which is essential for efficient N management in commercial crops. The results obtained here show the beginning of vegetative stage (V1–V9) significantly affects the prediction of all N status parameters. The dry leaf biomass (DLB), leaf area index (LAI), leaf nitrogen uptake (LNU), and nitrogen nutrition index (NNI) can be adequately predicted with combinations of just two VIs. These results show the importance of using active sensors with more than two fixed bands, preferably including a red‐edge band, for effective crop N status estimation.

Double-pulse stand-off explosive vapour detection system for flexible perilous materials

The paper presents the analyses of explosive material sensors. Sensors are described and assigned to the X and radiation, optical radiation sensors, as well as detectors applied in gas chromatography, electrochemical and chemical sensors. Furthermore, neutron techniques and magnetic resonance devices were analysed; the particular attention of the optoelectronic sensors of explosive devices. These robots used in the military applications employed with the integrated system, including video screens, sensors, gripper and cameras. The fighting robots also have different shapes according to the purposes of each robot. Here, the new system is proposed with the help of low power Zigbee wireless sensor network to trace out the intruders (unknown persons) and the robot will take the necessary action automatically. Thus, the proposed system, an intelligent unmanned robot (IUR) using Zigbee saves human life and reduces manual error in defence side. The specially designed robotic system to preserve human life and protects the country from enemies.

DOUBLE-PULSE STAND-OFF EXPLOSIVE VAPOUR DETECTION SYSTEM FOR FLEXIBLE PERILOUS MATERIALS

The paper presents the analyses of explosive material sensors. Sensors are described and assigned to the X and radiation, optical radiation sensors, as well as detectors applied in gas chromatography, electrochemical and chemical sensors. Furthermore, neutron techniques and magnetic resonance devices were analysed; the particular attention of the optoelectronic sensors of explosive devices. These robots used in the military applications employed with the integrated system, including video screens, sensors, gripper and cameras. The fighting robots also have different shapes according to the purposes of each robot. Here, the new system is proposed with the help of low power Zigbee wireless sensor network to trace out the intruders (unknown persons) and the robot will take the necessary action automatically. Thus, the proposed system, an intelligent unmanned robot (IUR) using Zigbee saves human life and reduces manual error in defence side. The specially designed robotic system to preserve human life and protects the country from enemies.

Investigation the doping influence on the characteristics of optical fiber for radiation dosimeter applications

Abstract The influence of doping the single mode fiber cladding and core with germanium (Ge) and phosphorus (P) on the optical properties of fiber had been investigated in this work. This is done using the Finite Elements Method through the COMSOL Multiphysics simulation program. This study will be very helpful for designing optical fiber radiation sensors (Dosimeters) to investigate the influence of different -doping on the fiber sensitivity under different radiations like X-ray, pulsed X-ray, and Gamma-ray.

New model for explaining the over-response phenomenon in percentage of depth dose curve measured using inorganic scintillating materials for optical fiber radiation sensors.

Inorganic scintillating material used in optical fibre sensors (OFS) when used as dosimeters for measuring percentage depth dose (PDD) characteristics have exhibited significant differences when compared to those measured using an ionization chamber (IC), which is the clinical gold standard for quality assurance (QA) assessments. The percentage difference between the two measurements is as high as 16.5% for a 10 × 10 cm2 field at 10 cm depth below the surface. Two reasons have been suggested for this: the presence of an energy effect and Cerenkov radiation. These two factors are analysed in detail and evaluated quantitatively. It is established that the influence of the energy effect is only a maximum of 2.5% difference for a beam size 10 × 10 cm2 compared with the measured ionization chamber values. And the influence of the Cerenkov radiation is less than 0.14% in an inorganic scintillating material in the case of OFS when using Gd2O2S:Tb as the luminescent material. Therefore, there must be other mechanisms leading to over-response. The luminescence mechanism of inorganic scintillating material is theoretically analysed and a new model is proposed and validated that helps explain the over-response phenomenon.

Method for optical radiation sensor signal irregularity correction in the computer microscopy system

The paper presents a preliminary study to adjust for the irregularity of the signal space of a sensor of optical radiation in the computer microscopy system. A method for correcting the uneven signal of the optical radiation sensor in computer microscopy systems is proposed based on the results of the research. The proposed approach will allow to correct the results of measurements of the characteristics of objects obtained by light microscopy in combination with computer data processing.

The Development of New Dosimetry System using an Optic-Disk Radiation Sensor for Pencil Beam Scanning Mode

A measurement of integral depth dose profile (IDD) for the pencil beam scanning (PBS) is very important for the accurate delivery of dose to the target volume with a good conformity. In the beam commissioning process for PBS treatment method, the IDD profiles are commonly acquired for the beam modeling of treatment planning system. In this study, we fabricated an optic-disk radiation sensor (ODRS) and characterized the photoluminescence signal generated from an optical disk as fundamental research for the development and evaluation of a new dosimetric system for pencil beam proton therapy using an ODRS system. The relative IDD curve of proton beam was obtained by ODRS system and analyzed with it measured by ion chamber. We proposed an innovative method using a signal generated in clear plastic optic disk. We fabricated the ODRS system for measuring the photoluminescence signal induced by therapeutic pencil beam proton beams, respectively. Homemade phantoms based optic disk made of poly methyl methacrylate were fabricated to allow the optic disk to be exposed in the direction of the beam inside a water phantom capable of 3D operation. The photoluminescence signal generated from the optic disk by the proton beam was converted to an electric signal by a multi-anode photomultiplier tube (MAPMT: H7546, Hamamatsu Photonics, Shizuoka, Japan) connected to the plastic optic fiber surrounding the disk, NI-DAQ system, which allows us to check in real time through a notebook computer. The basic characteristics as the dosimetry sensor for this system based optic disk are described. The linearity relationship between the output according to the dose and dose rate measured using the ion chamber and the photoluminescence signal obtained by this system was confirmed, and the result was shown to be linear. The calibration factor for the energy was found to be close to zero, and it was confirmed that the energy dependence on the optic disk need not be considered. The relative IDD profiles were obtained using the photoluminescence signal generated by the pencil beam irradiation with two energies of 99.9 and 162.1 MeV in this system, which was compared with the curve measured by the Bragg chamber. The IDD results obtained by optic disk radiation sensor indicated good agreement without any correction process with the one by Bragg chamber. In this study, we developed a clear optic disk-based system to evaluate the characteristics for PBS beam dosimetry. An advantage of this system is that it can be easily extended to a two-dimensional array system for application in the PBS beam dosimetry. As a further study, we are developing the ODRS system which can measure the depth dose at each depth in 2 mm increments with respect to the direction of the PBS beam using a 2 mm thick disk array.

YAG:Ce-Phosphor Scintillators for Optical Fiber Radiation Sensors With High Temporal Resolution

A miniature optical fiber real-time X-ray radiation sensor based on plastic optical fiber coupled with a fast decay time trivalent cerium-activated yttrium aluminum garnet Y3Al5O12 (YAG:Ce) scintillator material is reported. The YAG material was tested in powder and ceramic form. Three separate sensors were irradiated three times on a Siemens Artiste linear accelerator (linac). The measured light output of the YAG:Ce ceramic to the detector at the distal end of the fiber is 4.52 times greater than the YAG:Ce powder, and its output intensity detected by photon counter is further increased 2.52 times using a two-layer highly reflective Teflon tape. The sensor made with YAG:Ce powder shows excellent repeatability, being a maximum of 0.36 %, but the value using YAG:Ce ceramic exhibits orientation sensitivity when located in orthogonal positions relative to the X-ray beam. To the best of our knowledge, the work described in this letter is the first instance of the direct high temporal resolution detection of the individual (circa 3.9 ms) output of X-ray light pulses of clinical linacs. The experimental results of pulsewidths are in good agreement with the manufacturer’s stated value of $3.45~\pm ~0.21~\mu \text{s}$ .

Distributed Optical Fiber Radiation Sensing in the Proton Synchrotron Booster at CERN

In this paper, we report on the development and first deployment of a distributed optical fiber radiation sensor (DOFRS) for the online monitoring of radiation levels in the high-energy accelerator facilities of CERN. The DOFRS is composed of two basic parts: a set of suitably chosen radiation sensitive optical fibers (OFs), to be installed in the machine tunnel, and an optical time domain reflectometer (OTDR), to be installed in a radiation-free area. We carried out a calibration of the radiation response of a P-doped multimode OF under 60Co $\gamma $ -rays and in the mixed-field radiation environment of the CHARM facility at CERN. By performing OTDR measurements, we are able to probe the radiation-induced attenuation in the OF along its length and calculate the deposited radiation dose with a spatial resolution of 1 m. In this paper, we describe the main features associated with DOFRS implementation in the proton synchrotron booster (PSB) at CERN. We also report the first results obtained from the monitoring of PSB radiation levels since its recommissioning in April 2017. The performances and advantages of the DOFRS system are discussed.

Influence of Ionizing Radiation and the Role of Thiol Ligands on the Reversible Photodarkening of CdTe/CdS Quantum Dots.

We investigate the influence of high energy photons and thiol ligands on the photophysical properties of sub-monolayer CdTe/CdS quantum dots (QDs) immobilized in porous silica (PSiO2) scaffolds. The highly disperse, uniform distributions of QDs in a three-dimensional PSiO2 framework ensure uniform interaction of not only radiation but also subsequent surface repassivation solutions to all immobilized QDs. The high optical densities of QDs achieved using PSiO2 enable straightforward monitoring of the QD photoluminescence intensities and carrier lifetimes. Irradiation of QDs in PSiO2 by high energy photons, X-rays, and γ-rays leads to dose-dependent QD photodarkening, which is accompanied by accelerated photooxidative effects in ambient environments that give rise to blue-shifts in the peak QD emission wavelength. Irradiation in an oxygen-free environment also leads to QD photodarkening but with no accompanying blue-shift of the QD emission. Significant reversal of QD photodarkening is demonstrated following QD surface repassivation with a solution containing free-thiols, suggesting reformation of a CdS shell, etching of surface oxidized species, and possible reduction of photoionized dark QDs to a neutral, bright state. Permanent lattice displacement damage effects may contribute toward some irreversible γ radiation damage. This work contributes to an improved understanding of the influence of surface ligands on the optical properties of QDs and opens up the possibilities of engineering large area, low-cost, reuseable, and flexible QD-based optical radiation sensors.

Measurement of Gamma-Rays Induced Luminescence Generated in a Sapphire Based Fiber-Optic Radiation Sensor

In this study, we fabricated a sapphire based fiber-optic radiation sensor. To evaluate the fiber- optic radiation sensor, we measured the spectrum and intensity of the luminescence generated from the fiber-optic radiation sensor according to the thickness of the PMMA block by irradiation of gamma rays emitted from a Co-60 source. And the result was compared with the value calculated from the formula of Lambert-Beer.

SU‐E‐T‐159: Characteristics of Fiber‐Optic Radiation Sensor for Proton Therapeutic Beam

Purpose:A fiber‐optic radiation sensor using Cerenkov radiation has been widely studied for use as a dosimeter for proton therapeutic beam. Although the fiber‐optic radiation sensor has already been investigated for proton therapeutic, it has been examined relatively little work for clinical therapeutic proton beams. In this study, we evaluated characteristics of a fiber‐optic radiation sensor for clinical therapeutic proton beams. We experimentally evaluated dose‐rate dependence, dose response and energy dependence for the proton beam.Methods:A fiber‐optic radiation sensor was placed in a water phantom. Beams with energies of low, middle and high were used in the passively‐scattered proton therapeutic beam at the National Cancer Center in Korea. The sensor consists of two plastic optical fibers (POF). A reference POF and 2 cm longer POF were used to utilize the subtraction method for having sensitive volume. Each POF is optically coupled to the Multi‐Anode Photo Multiplier Tube (MAPMT) and the MAPMT signals are processed using National Instruments Data Acquisition System (NI‐DAQ). We were investigated dosimetric properties including dose‐rate dependence, dose response and energy dependence.Results:We have successfully evaluated characteristics of a fiber optic radiation sensor using Cerenkov radiation. The fiber‐optic radiation sensor showed the dose response linearity and low energy dependence. In addition, as the dose‐rate was increased, Cerenkov radiation increased linearly.Conclusion:We evaluated the basic characteristics of the fiber optic radiation sensor, the dosimetry tool, to raise the quality of proton therapy. Based on the research, we developed a real time dosimetry system of the optic fiber to confirm the real time beam position and energy for therapeutic proton pencil beam.

Study of Traps in Special Doped Optical Fiber Radiation Sensors via Glow Curve Analysis

Thermoluminescence dosimeters (TLDs) are widely used, serving the needs of various radiation applications. In recent times optical fibers have been introduced as alternatives to more conventional phosphor-based TLD systems, with many efforts being carried out to improve their thermoluminescence (TL) yield. While there have been extensive studies of many of the various TLD characteristics of optical fibers, including TL response, linearity, reproducibility, repeatability, sensitivity and fading, far more limited studies have concerned dependence on the type of TL activator used in optical fibers, promoting the TL mechanism. Present study focuses on TLD glow curves analysis for five different doped optical fibers that have been subjected to photon and electron irradiation. Trap parameters such as activation energy and frequency factors have been obtained from second order kinetics analysis, based on computerized glow curve deconvolution. An interesting observation is that co-doped fibers typically leads to enhanced TL characteristics, pointing to a need for optimization of the choice and levels in use of co-dopants.

Sensors and Systems for the Detection of Explosive Devices - An Overview

Sensors and Systems for the Detection of Explosive Devices - An Overview The paper presents analyses of current research projects connected with explosive material sensors. Sensors are described assigned to X and γ radiation, optical radiation sensors, as well as detectors applied in gas chromatography, electrochemical and chemical sensors. Furthermore, neutron techniques and magnetic resonance devices were analyzed. Special attention was drawn to optoelectronic sensors of explosive devices.

Radiation response behaviour of Al codoped germano-silicate SM fiber at high radiation dose

Radiation response behaviour of Ge+Al doped SM fiber fabricated by the solution doping process has been studied at room temperature with respect to 1310nm transmission wavelength under three different dose rates of 200, 400 and 600Rad/min to compare with that of standard Er doped as well as Ge doped SM fibers. Their radiation sensitivity has been observed with variation of dose rates, transmission wavelength along with their recovery nature. Radiation response behaviour of Al doped SM fiber is found to be slightly non-linear in nature with very low dose rate dependency. No saturation level was found upto 13Krad cumulative dose. Thermobleaching as well as photobleaching phenomena have also been studied. Gamma irradiated Al doped preform shows an absorption peak at around 300nm due to generation of Al (E′) defect center and gets annihilated after thermobleaching process. Gamma irradiated Al doped SM fiber shows prominent photobleaching effect on their optical attenuation with respect to the 850nm transmission wavelength. From ESR study resonance signals for Al3+ related radiation-induced defect centers are not clearly observed in this study. A very weak hyperfine pattern has been observed for gamma irradiated Al doped preform sample. The high radiation sensitivity along with linear response behaviour, low recovery and almost dose rate independence behaviour of the material system of Ge+Al codoped SM core optical fiber under gamma radiation shows their potential for application as fiber optic radiation sensor in comparison to the universal standard erbium doped SM fiber.