사용후핵연료 집합체 모사장치를 이용한 광섬유 체렌코프 방사선 센서 시스템의 성능평가

Cerenkov radiation, which is produced by charged particles that pass through optical fibers with a velocity greater than that of light, is frequently regarded as a severe noise signal in a fiber-optic radiation sensor consisting of a scintillator and an optical fiber. Since the spectral range of Cerenkov radiation is very broad and covers that of light outputs from a scintillator, Cerenkov radiation generated in optical fibers is also acquired by a photodetector. However, Cerenkov radiation can be a significant signal when we measure the intensities of Cerenkov radiation generated from fixed length of optical fibers because it is one of the signals induced by interactions between radiations and optical fibers. In this study, gamma-ray induced Cerenkov radiation generated in silica and plastic optical fibers was measured in order to select an efficient optical fiber for producing Cerenkov radiation. The intensities and the spectra of Cerenkov radiation generated in the optical fibers were measured using a spectrometer. As the results, the intensities of Cerenkov radiation generated in silica and plastic optical fibers have peak wavelengths at approximately 500 nm. Also, the intensity of Cerenkov radiation obtained using a plastic wavelength shifting fiber was the highest among all sample optical fibers.

Silica optical fibres (SOF) are established for the use of communicating digital data and numerous applications including structure health monitoring. However, SOFs exhibit drawbacks such as brittleness, low strain and signal attenuation due to bending. These drawbacks limit the use of SOF as embedded sensors for monitoring composite structures’ internal health. Unlike SOFs, the relatively newly developed polymer optical fibres (POF) do not possess such drawbacks and they are able to monitor the health of fibre-based composite structures. Bending in optical fibres is a major concern since this causes signal attenuation at bending points. Integrating optical fibres into a woven preform requires bending because of the crimping that occurs as a result of weave interlacing. The main objective of this research was to evaluate the effect of the macrobending of optical fibres on signal power integrity. The goal is to design optical fibre sensors embedded in woven preforms that have high sensitivity for monitoring the health of composite structures. Newly developed Graded Index Perfluorinated POF (GI-PF-POF) and two types of SOFs were evaluated in a three-point macrobending test bed using a laser light source. A systematic experimental design was executed to evaluate the optical fibres’ signal loss as a result of the bending radius, bending deflection and wrap angle of optical fibre around the middle rod of the test bed. The results showed that POF provides higher signal sensitivity and greater robustness against signal attenuation under bending when compared to SOF. The work also unveiled the bending radius of optical fibres at which minimum or no signal loss occurred. This finding is essential for designing embedded optical fibre sensors with high sensitivity.

Aptamers represent the next frontier as biorecognition elements in biosensors thanks to a smaller size and lower molecular weight with respect to antibodies, more structural flexibility with the possibility to be regenerated, reduced batch-to-batch variation, and a potentially lower cost. Their high specificity and small size are particularly interesting for their application in optical biosensors since the perturbation of the evanescent field are low. Apart from the conventional plasmonic optical sensors, platforms based on silica and plastic optical fibers represent an interesting class of devices for point-of-care testing (POCT) in different applications. The first example of the coupling between aptamers and silica optical fibers was reported by Pollet in 2009 for the detection of IgE molecules. Six years later, the first example was published using a plastic optical fiber (POF) for the detection of Vascular Endothelial Growth Factor (VEGF). The excellent flexibility, great numerical aperture, and the large diameter make POFs extremely promising to be coupled to aptamers for the development of a sensitive platform easily integrable in portable, small-size, and simple devices. Starting from silica fiber-based surface plasmon resonance devices, here, a focus on significant biological applications based on aptamers, combined with plasmonic-POF probes, is reported.

Gait analysis is of major importance in physical rehabilitation scenarios, lower limbs diseases diagnosis and prevention. Foot plantar pressure is a key parameter in the gait analysis and its dynamic monitoring is crucial for an accurate assessment of gait related pathologies and/or rehabilitation status evolution. It is therefore critical to invest effort in research for foot plantar analysis technologies. From that perspective, optical fiber sensors appear to be an excellent solution, given their sensing advantages for medical applications, when compared with their electronic counterparts. This chapter explores the use of optical fiber Bragg grating (FBG) sensors, both in plastic and silica optical fiber, to dynamically monitor the foot plantar pressure. An array of FBGs was integrated in a specially designed cork insole, with the optical sensors placed at key pressure points for analysis. Both insoles, containing plastic and silica optical fiber sensors, were tested for dynamic gait monitoring and body center of mass displacement, showing the reliability of this sensing technology for foot plantar pressure monitoring during gait motion.

In this work, two silica optical fiber (SOF) sensors are developed exploiting a novel sensing principle based on two SOFs coupled via a lens made on the tip of the launching SOF and covered by molecularly imprinted polymers (MIPs). Another SOF collects the focused light through a sensitive lens. In particular, the lens is formed by a fusion splicing machine, while the MIP layer is deposited on the lens by dip-coating. As a proof-of-concept, a MIP for the detection of 4-chloro-2-methylphenoxyacetic acid (MCPA) is used. Two sensor configurations are exploited by using, as the launching SOF, a narrow-core (NC) optical fiber or a large-core (LC) optical fiber, in order to tune the detection range. When the analyte (MCPA) interacts with the MIP on the lens, the MIP's refractive index changes, and therefore changes the focal length of the lens on the launching SOF, altering the intensity of the collected light. To demonstrate the feasibility of the sensing principle, experimental results for the MCPA detection in water were obtained by exploiting both sensor configurations based on NC and LC SOFs. The best sensor configuration based on the LC SOF presents a limit of detection (LOD) of 8 pM and a detection range from 8 pM to 1 nM. In contrast, the NC SOF sensor configuration achieves a LOD of about 89 nM and a detection range from 89 nM to 54 μM. Therefore, by replacing the launching SOF, complementary MCPA detection ranges are achieved.

The paper reports the numerical analysis and some experimental results relative to an optical sensor system based on Surface Plasmon Resonance (SPR) at the interface of a liquid sample and a sandwiched structures realized starting from the exposed core of a Plastic Optical Fiber (POF). The advantages of POF sensors is that they are simpler to manufacture than those based on silica optical fibers. In the scientific literature there are only simple POF sensors based on laterally polished bent structures prepared along a plastic optical fiber [1]. In this paper different POF sensor configurations are simulated and experimentally tested. The classical geometry of sensors based on SPR in silica optical fiber is adapted and borrowed for Plastic Optical Fibers [2], so representing a simple approach to low cost plasmonic sensing.

In this research, we propose a novel method for detecting thermal neutrons with a fiber-optic radiation sensor using the Cerenkov effect. We fabricate a fiber-optic radiation sensor that detects thermal neutrons with a Gd-foil, a rutile crystal, and a plastic optical fiber. The relationship between the fluxes of electrons inducing Cerenkov radiation in the sensor probe of the fiber-optic radiation sensor and thermal neutron fluxes is determined using the Monte Carlo N-particle transport code simulations. To evaluate the fiber-optic radiation sensor, the Cerenkov radiation generated in the fiber-optic radiation sensor by irradiation of pure thermal neutron beams is measured according to the depths of polyethylene.

The chemistry of sol-gel derived silica and refractive metal oxide has been systematically studied. Sol-gel processes have been developed for preparing porous silica and semiconductor metal oxide materials. Micelle/reversed micelle techniques have been developed for preparing nanometer sized semiconductor metal oxides and noble metal particles. Techniques for doping metal ions, metal oxides and nanosized metal particles into porous sol-gel material have also been developed. Optical properties of sol-gel derived materials in ambient and high temperature gases have been studied by using fiber optic spectroscopic techniques, such as fiber optic ultraviolet/visible absorption spectrometry, fiber optic near infrared absorption spectrometry and fiber optic fluorescence spectrometry. Fiber optic spectrometric techniques have been developed for investigating the optical properties of these sol-gel derived materials prepared as porous optical fibers or as coatings on the surface of silica optical fibers. Optical and electron microscopic techniques have been used to observe the microstructure, such as pore size, pore shape, sensing agent distribution, of sol-gel derived material, as well as the size and morphology of nanometer metal particle doped in sol-gel derived porous silica, the nature of coating of sol-gel derived materials on silica optical fiber surface. In addition, the chemical reactions of metal ion, nanostructured semiconductor metal oxides and nanometer sized metal particles with gas components at room temperature and high temperatures have also been investigated with fiber optic spectrometric methods. Three classes of fiber optic sensors have been developed based on the thorough investigation of sol-gel chemistry and sol-gel derived materials. The first group of fiber optic sensors uses porous silica optical fibers doped with metal ions or metal oxide as transducers for sensing trace NH{sub 3} and H{sub 2}S in high temperature gas samples. The second group of fiber optic sensors uses sol-gel derived porous silica materials doped with nanometer particles of noble metals in the form of fiber or coating for sensing trace H{sub 2}, NH{sub 3} and HCl in gas samples at for applications ambient temperature. The third classes of fiber optic sensors use sol-gel derived semiconductor metal oxide coating on the surface of silica optical fiber as transducers for selectively sensing H{sub 2}, CH{sub 4} and CO at high temperature. In addition, optical fiber temperature sensors use the fluorescence signal of rare-earth metal ions doped porous silica optical fiber or the optical absorption signal of thermochromic metal oxide materials coated on the surface of silica optical fibers have also been developed for monitoring gas temperature of corrosive gas. Based on the results obtained from this project, the principle of fiber optic sensor techniques for monitoring matrix gas components as well as trace components of coal gasification derived syngas has been established. Prototype sensors for sensing trace ammonia and hydrogen sulfide in gasification derived syngas have been built up in our laboratory and have been tested using gas samples with matrix gas composition similar to that of gasification derived fuel gas. Test results illustrated the feasibility of these sensors for applications in IGCC processes.

The upside down taper lens (UDTL) optical fiber ends are formed by a heating method. This new type of microlens can be used to make optical fiber connector between two fibers. In this paper, using plastic optical fiber, a single installation which are needed in the making UDTL fiber ends is described. The making method of this type plastic optical fiber end is introduced. Theoretically, using 1D heat conductor model, we analyze the forming tendency during the heating of the end of a plastic fiber. Experiments of the coupling between two plastic optical fibers with UDTL ends are given. The testing results of the connector shows that this novel optical fiber device can improve the coupling efficiency and provided a potentially inexpensive, simple and direct coupling method for fiber optic communication and fiber sensor systems.

The aim of this study was to develop and evaluate fiber-optic sensors for the remote detection of gamma rays in areas that are difficult to access, such as a spent fuel pool. The fiber-optic sensor consists of a light-generating probe, such as scintillators for radiation detection, plastic optical fibers, and light-measuring devices, such as PMT. The (Lu,Y)2SiO5:Ce(LYSO:Ce) scintillator was chosen as the light-generating probe. The (Lu,Y)2SiO5:Ce(LYSO:Ce) scintillator has higher scintillation efficiency than the others and transmits light well through an optical fiber because its refraction index is similar to the refractive index of the optical fiber. The fiber-optic radiation sensor using the (Lu,Y)2SiO5:Ce(LYSO:Ce) scintillator was evaluated in terms of the detection efficiency and reproducibility for examining its applicability as a radiation sensor.

This review discusses a distributed beam loss monitor which is based on the Cherenkov effect in an optical fiber and which has been installed at the VEPP-5 Injection Complex at the Budker Institute of Nuclear Physics. The principle of the device operation consists in detecting the Cherenkov radiation generated in an optical fiber by relativistic charged particles that are produced in an electromagnetic shower when highly relativistic beam particles (electrons or positrons) hit the accelerator vacuum chamber wall. Our experiments used a photomultiplier tube (PMT) to detect the Cherenkov light. Knowing when the PMT signal arrives tells us where the beam loss occurs. Using a optical fiber allowed a detector spatial resolution of . The way to improve the resolution is to optimize the monitor working conditions and optical fiber and PMT parameters, potentially leading to a resolution of as fine as according to our estimates.

In this study, we measured scintillating and Cerenkov lights generated in a scintillating fiber-optic sensor using highenergy electron beams and a spectrometer. The spectrum of Cerenkov light generated in a plastic optical fiber was measured with a spectrometer and the intensities of Cerenkov light were measured for irradiated lengths of the plastic optical fiber by integrating the photon counts at every wavelength of the spectrum. The intensities of Cerenkov and scintillating lights were also characterized as a function of the incident angle of an electron beam from a clinical linear accelerator (CLINAC). To minimize or remove Cerenkov light, a subtraction method was employed using a background optical fiber.

In this study, we have fabricated one-dimensional fiber-optic radiation sensor array for high energy electron beam therapy dosimetry. Fiber-optic radiation sensor comprises an organic scintillator as a sensing volume, optical fiber as a light guider and photo-detector as a light measuring device. Usually, photomultiplier tube or photodiode is used as a photo-detector however we have tried to use a charge-coupled device as a scintillating light measuring system for one-dimensional fiber-optic radiation sensor array. This system can take an image of the proximal ends of one-dimensional fiber-optic sensor array and can measure light intensities of individual image of optical fibers simultaneously using simple imaging software. Charge-coupled device as a light measuring detector has many advantages which are easy in multi-dimensional measurements, high spatial resolution and relatively low cost. We have measured one-dimensional electron beam distributions in a PMMA phantom with different energies and field sizes of electron beam using a fiber-optic sensor and a charge-coupled device. Also, the percentage depth dose curves for high energy electron beams are obtained.

The present article summarizes the results of a study of optical Cherenkov radiation (ChR) spectral properties both theoretically and experimentally. This type of radiation has a continuous spectral distribution which allows to use it in different fields of physics as for charged particle identification or generation of intense THz radiation. By exploiting the frequency dependency of the target permittivity it is possible to observe quasi–monochromatic radiation. A theoretical model based on a surface current approach is presented which allows to predict angular and spectral properties of ChR. In order to test the model predictions, an experiment was carried out using 855 MeV electrons and a 0.2 mm thick quartz target as radiator which could be rotated with respect to the beam axis. Quasi–monochromatic ChR was observed with a spectrometer placed at a fix observation angle, and tilting the radiator crystal offered the possibility to tune the radiation wavelength. The monochromatization effect is attributed to the frequency dependency of the quartz permittivity, and taking into account the refraction law for emitted ChR crossing the boundary between radiator target and vacuum it is possible to deduce a dispersion relation which connects ChR wavelength and outgoing photon angle - or in an alternative way ChR wavelength and target tilt angle for fixed observation angle. The dispersion relation is clearly confirmed in the experiment, and the model predictions show a satisfactory agreement with the measurements. Exploiting the ChR monochromatization mechanism might offer versatile tools which can find applications for example in beam diagnostics at modern particle accelerators.

Several approaches have been previously investigated which utilize fiber optic sensors to determine the relative humidity of air. Such devices typically have the advantage of higher sensitivity and quantitative precision compared to traditional chemical indicators. For example, the use of an optical fiber evanescent sensor for humidity measurements has been described by Russell and Fletcher1. In their device, a moisture sensitive cobalt chloride/gelatin film is immobilized on a 12cm long silica optical fiber as the humidity probe. Ballantine and Wohltjen described an optical waveguide humidity sensor that employed the same calorimetric reagent/polymer system on a glass capillary2. Zhu and Hieftje utilized a fluorescent fiber optic sensor for atmospheric humidity3 based on a dye entrapped within a polymer matrix. However, all of these sensors can only determine the relative humidity above 40% because of sensitivity limitations.