Plastic Scintillating Fibers Research Articles

Feasibility Analysis of Tritium Measurement in the Aqueous Medium Based on a Plastic Scintillating Fiber Array

Tritium causes internal dose hazards to humans. Currently, tritium in the environment mainly comes from nuclear power plants, and tritiated water (HTO) is the main form of liquid emission. Therefore, online monitoring activity of tritium in the aqueous medium is vital for protecting human health, and it can warn of the operation status of nuclear power plants. In this paper, we present an improved structure of plastic scintillating fiber (PSF) and a PSF array design, and the detection parameters of PSF arrays with different radii and lengths under different radius detection chambers are simulated using Geant4. Based on the simulation results, the detector is designed, and the minimum detectable activity concentration (MDAC) of the detector is calculated. With calculated MDACs down to 3.09 Bq/L, the proposed design can meet the Chinese requirements for HTO release of inland nuclear power plants of <100 Bq∙L−1. Therefore, the detector designed with a PSF array can be applied to online monitoring of tritium in the aqueous medium.

Optimizing calibration factors of plastic scintillation fibers for improved accuracy of in situ radiocesium concentration measurements in bottom sediments of agricultural ponds

Optimizing calibration factors of plastic scintillation fibers for improved accuracy of <i>in situ</i> radiocesium concentration measurements in bottom sediments of agricultural ponds

Plastic scintillation fiber with europium complexes for low-dose X-ray detection and long-distance imaging

This work produces a new type of plastic scintillation fiber with excellent performances to realize X-ray detection and imaging.

Evaluation of plastic scintillating fibers coating technique for muon imaging detector using a Compton-coincidence-technique system

This study is devoted to studying the performance of plastic scintillating fibers (PSFs) for a high-position-resolution muon imaging detector. A test system based on the Compton coincidence technique is designed to study the light collection of the PSFs. When Compton scattering occurs between the PSFs and gamma ray emitted by the collimated radioactive source, the PSF detector has detected the definite energy of recoiled electrons, and the coincidence detector has detected the energy of scattered photons. Four groups of PSFs were tested, three of which were wrapped with the Enhanced Specular Reflector (ESR) in different ways. The experimental results show that the light collection of the PSF detector can be increased by wrapping the PSFs with ESR and leaving an air gap between the PSF and the ESR. Meanwhile, the light collection is increased while the position where Compton scattering occurs in the PSF is closer to the silicon photomultiplier (SiPM). This study provides a method for measuring the light collection in narrow PSFs. In conclusion, the presence and fine wrapping of the ESR ensure the isolation and position accuracy in the arrays of PSFs.

An Innovative Fluorescent Fiber Sensor Based on Ce/Tb Co-Doped Silica Fiber for Partial Discharge Detection

A novel fluorescent fiber sensor based on cerium (Ce) and terbium (Tb) co-doped silica fiber (CTDSF) for partial discharge (PD) detection is proposed. The luminescence mechanism and PD detection principle of CTDSF are theoretically investigated. The CTDSF is fabricated using the rod-in-tube technique combined with the CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser-heated drawing method. The intense emission peak of Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ions located at 542 nm ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> - <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> transition) is excited at 302 nm, which indicates the energy transfer between Ce <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ions. Moreover, the excitation peak region near 302 nm is well aligned with the PD light emission spectrum. Subsequently, the PD time domain signals of the needle-plate defect are experimentally measured by utilizing the CTDSF sensor, high-frequency current transformer, and plastic scintillation fiber (PSF). And the experimental results demonstrate that the CTDSF sensor can detect PD signals and has an excellent PD detection linear response with a sensitivity of 0.22 ns∙V/pC. Furthermore, the sensitivity of the CTDSF sensor is approximately 2.4 times dramatically higher than that of the PSF sensor. The CTDSF sensor integrated with the all-fiber system is predicted to have a wide range of potential applications for online PD detection.

Position detection of a beta particle emitter by utilizing self-absorption in a scintillation fiber.

Self-absorption in a plastic scintillation fiber can be utilized to determine the incident position of single beta particles. A dichroic mirror directs scintillation photons with shorter wavelengths to one Si photomultiplier and those with longer wavelengths to another. An index calculated from the two signals is a monotonic function of the distance between the tip of the fiber and the incident point. Once this relation is known, one can determine the distance from the two measurables. In an experiment, such a calibration curve was acquired to detect the position of a 90Sr source up to a distance of 240 cm. The average total number of photoelectrons for a single beta particle was about 15-17. Depending on the propagation distance in the scintillation fiber, they were unevenly divided by the two photodetectors.

Development of a muon detector based on a plastic scintillator and WLS fibers to be used for muon tomography system

Muon tomography is a useful method for monitoring special nuclear materials (SNMs) such as spent nuclear fuel inside dry cask storage. Multiple Coulomb scattering of muons can be used to provide information about the 3-dimensional structure and atomic number(Z) of the inner materials. Tomography using muons is less affected by the shielding material and less harmful to health than other measurement methods.We developed a muon detector for muon tomography, which consists of a plastic scintillator, 64 long wavelength-shifting (WLS) fibers attached to the top of the plastic scintillator, and silicon photomultipliers (SiPMs) connected to both ends of each WLS fiber. The muon detector can acquire X and Y positions simultaneously using a position determination algorithm.The design parameters of the muon detector were optimized using DETECT2000 and Geant4 simulations, and a muon detector prototype was built based on the results. Spatial resolution measurement was performed using simulations and experiments to evaluate the feasibility of the muon detector. The experimental results were in good agreement with the simulation results. The muon detector has been confirmed for use in a muon tomography system.

Feasibility study of a prototype muon tomography system based on a plastic scintillator and WLS fibers

Muon tomography is a technique for monitoring special nuclear material, such as uranium, inside the shielding material. It is a 3D imaging system capable of identifying atomic number (Z) using muon particles, high energy natural radiation. The following technique shows an advantage in no radiation exposure due to its usage of naturally occurring cosmic ray muons.In this study, a prototype muon tomography system was developed using four muon detectors in top and bottom structures. The four muon detectors based on a plastic scintillator and WLS fibers were implemented in the previous study. Two detectors above the target object and the other two below the target object measure a muon’s incoming and outgoing trajectories, respectively. Four detectors constituting the prototype were connected by coincidence to confirm the muon detection.The purpose of this study was to develop the prototype muon tomography system and to reconstruct the image of the high-Z material, such as lead and uranium. The performance of the prototype was confirmed by imaging under various conditions, such as measurement time, position, and thickness changes, using lead blocks. In addition, the feasibility of the prototype was verified by performing imaging using three materials with different atomic numbers, such as lead, iron, and aluminum.

Experimental Study on the Localization and Estimation of Radioactivity in Concrete Rubble Using Image Reconstruction Algorithms

To reduce a large amount of contaminated concrete rubble stored in the Fukushima Daiichi Nuclear Power Station site, recycling low-radioactivity rubble within the site is a possible remedy. To promote recycling while ensuring safety, not only the average radioactivity but also the radioactivity distribution of concrete rubble should be efficiently evaluated because the details of rubble contamination caused by the accident remain unclear and likely include hotspots. However, evaluating inhomogeneous contamination of thick and/or dense materials is difficult using previous measurement systems, such as clearance monitors. This study experimentally confirmed the potential applicability of image reconstruction algorithms for radioactivity distribution evaluation in concrete rubble filled in a chamber. Radiation was measured using plastic scintillation fiber (PSF) around the chamber ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50\times 50\times40$ </tex-math></inline-formula> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ). Localized hotspots were simulated using standard sources of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs, which is one of the main nuclides of contaminated rubble. The radioactivity distribution was calculated for 100 or 50 voxels (voxel size: (10 cm) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> or 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 10\times20$ </tex-math></inline-formula> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) constituting the chamber. For 100 voxels, inner hotspots were undetected, whereas for 50 voxels, both inner and surface hotspots were reconstructible. The distribution evaluated using the maximum likelihood expectation–maximization (ML-EM) algorithm was the most accurate; the average radioactivity was estimated within 70% accuracy in all seven cases.

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.

3D cosmic-ray muon tomography using portable muography detector

A feasibility demonstration of three-dimensional (3D) muon tomography was performed for infrastructure equivalent targets using the proposed portable muography detector. For the target, we used two sets of lead blocks placed at different heights. The detector consists of two muon position-sensitive detectors, made of plastic scintillating fibers (PSFs) and multi-pixel photon counters (MPPCs) with an angular resolution of 8 msr. In this work, the maximum likelihood-expectation maximization (ML-EM) method was used for the 3D imaging reconstruction of the muography. For both simulation and experiment, the reconstructed positions of the blocks produce consistent results with prior knowledge of the blocks' arrangement. This result demonstrates the potential of the 3D tomographic imaging of infrastructure by using seven detection positions for portable muography detectors to image infrastructure scale targets.

Characterization of an Innovative Detector Based on Scintillating Fiber for Personalized Computed Tomography Dosimetry.

For technical and radioprotection reasons, it has become essential to develop new dosimetric tools adapted to the specificities of computed tomography (CT) to ensure precise and efficient dosimetry since the current standards are not suitable for clinical use and for new CT technological evolution. Thanks to its many advantages, plastic scintillating fibers (PSF) is a good candidate for more accurate and personalized real-time dosimetry in computed tomography, and the company Fibermetrix has developed a new device named IVISCAN® based on this technology. In this study, we evaluated performances of IVISCAN® and associated uncertainties in terms of dose-rate dependence, angular dependence, stability with cumulative dose, repeatability, energy dependence, length dependence, and special uniformity in reference and clinical computed tomography beam qualities. For repeatability, the standard deviation is less than 0.039%, and the absolute uncertainty of repeatability lies between 0.017% and 0.025%. The deviation between IVISCAN® and the reference regarding energy dependence is less than 1.88% in clinical use. Dose rate dependence results show a maximum deviation under ±2%. Angular dependence standard deviation σ is 0.8%, and the absolute uncertainty was 1.6%. We observed 1% of variation every 50 Gy steps up to a cumulative dose of 500 Gy. Probe response was found to be independent of the PSF length with a maximum deviation < 2.7% between the IVISCAN® probe and the 1 cm PSF probe. The presented results demonstrated that IVISCAN® performances are in accordance with metrology references and the international standard IEC61674 relative to dosemeters used in X-ray diagnostic imaging and then make it an ideal candidate for real-time dosimetry in CT applications.

Performance of a plastic scintillation fiber dosimeter based on different photoelectric devices

Performance of a plastic scintillation fiber dosimeter based on different photoelectric devices

Comparison of theoretical and machine learning models to estimate gamma ray source positions using plastic scintillating optical fiber detector

In this study, one-dimensional gamma ray source positions are estimated using a plastic scintillating optical fiber, two photon counters and via data processing with a machine learning algorithm. A nonlinear regression algorithm is used to construct a machine learning model for the position estimation of radioactive sources. The position estimation results of radioactive sources using machine learning are compared with the theoretical position estimation results based on the same measured data. Various tests at the source positions are conducted to determine the improvement in the accuracy of source position estimation. In addition, an evaluation is performed to compare the change in accuracy when varying the number of training datasets. The proposed one-dimensional gamma ray source position estimation system with plastic scintillating fiber using machine learning algorithm can be used as radioactive leakage scanners at disposal sites.

Tapered fiber radiation sensor based on Ce/Tb:YAG crystals for remote γ-ray dosimetry.

A novel tapered fiber-optic radiation sensor (TFRS) based on cerium (Ce) and terbium (Tb) co-doped YAG scintillation crystals is demonstrated for the first time. Using the CO2 laser-heated method, a Ce/Tb:YAG crystal is well embedded into silica glass cladding without any cracks. The scintillation light emitted from the YAG scintillation crystal can be directly coupled into the derived silica optical fiber by the tapered region. The loss of the derived optical fiber is 0.14 dB/cm, which is one order of magnitude lower than the 1.59 dB/cm of the YAG crystal in the TFRS. Subsequently, strong photo- and radio-luminescence of Tb3+ (5D4→7F5) ions in TFRS are achieved under ultraviolet light and high-energy ray excitation, respectively. In particular, a prominent remote radiation response of the TFRS is presented under excitation by γ-rays through fusion splicing with multimode optical fibers. The response is approximately four times larger than that of a plastic scintillation fiber (BCF-12) sensor. Furthermore, the results possess high stability as well as a good linearity between the radiation dose rate and the response intensity. The TFRS in combination with an all-silica fiber system is a promising candidate for remote radiation detection.

The ecological half-life of radiocesium in surficial bottom sediments of five ponds in Fukushima based on in situ measurements with plastic scintillation fibers.

Plastic scintillation fibers (PSFs) have been instrumental in in situ surface contamination surveys post the Fukushima Daichi Nuclear Power Plant accident. Their deployment to monitoring bottom sediments in aquatic environments provides the spatial extent of contamination over wide areas compared to discrete points as provided traditionally by sediment sampling. This study evaluated the wide area ecological half-life (Teco) of radiocesium concentration for surface sediments of five ponds in Fukushima using PSFs, monitoring data generated between 2013 and 2019. The least squares' regression method was employed to evaluate the Teco. Four ponds had a Teco ranging from 3.0 ± 0.3 years to 11.4 ± 2.3 years. A forest-catchment pond exhibited a relatively long Teco of 41.6 ± 55 years. Local variation in the Teco appears to be influenced by sedimentation as we demonstrated larger values for areas showing potential sedimentation in the forest catchment pond. This study demonstrates the importance of wide area in situ monitoring techniques, such as PSF, in providing an overview of the spatial-temporal trends of radiocesium in bottom sediments and confirms the importance of forests as secondary contaminant sources to their drainage.

A $16\times8$ Digital-SiPM Array With Distributed Trigger Generator for Low SNR Particle Tracking

This letter describes a 16 × 8-pixel array based on single-photon avalanche diodes (SPADs) optimized for the readout of a tracking detector based on plastic scintillation fibers targeting ultrafast neutrons. Each pixel of 125 × 250 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> size contains 30 SPADs, an 80-ps 10-b time-to-digital converter (TDC), a 5-b intensity counter, a finite state machine (FSM) that manages the recording of data and a three-word-deep FIFO memory for parallel acquisition and readout, achieving 32.1% pixel fill factor. A combined, programmable current-based local, and global triggering mechanism correlates the photon detection activity in time to distinguish asynchronous charged particle trace events from background noise even with a poor SNR.

Radiation-detection methods to counter radiological threats⋆

We propose two methods as means to counter radiological terrorist acts, such as dirty-bomb or silent-source attacks. The first proposal concerns a nuclear detection system using the security cameras already installed in public spaces. We describe a method to estimate radiation dose from the amount of noise in CCD images caused by neutron radiation. Several dosimeters subjected to neutron and gamma-ray irradiation (0.1mSv-1000mSv) were imaged by a CCD video camera. We confirmed that the amount of noise in the CCD images varied linearly with radiation exposure. We propose a warning system to uncover shielded nuclear materials or radiation exposure devices. The second proposal is a survey system of radiological residue using long scintillation fibers. After a dirty-bomb explosion, the first responders need to search for radiological samples for subsequent nuclear forensics. We developed a position-sensitive detector with 10m plastic scintillation fibers. The position resolution was found to be 50cm and the dynamic range extended from 0.05μ Sv/h to 300μSv/h. We also were able to perform real-time measurements of distributed sources in situ. Stand-off detection using this device helps in surveying contaminated areas.

A high DQE water-equivalent EPID employing an array of plastic-scintillating fibers for simultaneous imaging and dosimetry in radiotherapy.

First measurements of the imaging performance of a novel prototype water-equivalent electronic portal imaging device (EPID) designed for simultaneous imaging and dose verification in radiotherapy and previously characterized by our group for dosimetry are reported. Experiments were conducted to characterize the prototype's imaging performance relative to a standard commercial EPID and Monte Carlo (MC) simulations were performed to quantify the impact of several detector parameters on image quality and to inform the design of a proposed next-generation prototype. The prototype EPID utilizes an array of 3 cm long plastic-scintillating fibers in place of the metal plate/phosphor screen in standard EPIDs. Using a clinical 6 MV photon beam, the prototype's modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) were measured and compared to measurements taken using a standard commercial EPID. A sensitivity analysis was then performed using the MC model by quantifying these metrics while varying the values of several geometrical and optical transport parameters that were unspecified by the prototype manufacturer. Finally, the MC model was used to quantify the imaging performance of a proposed next-generation prototype incorporating 1.5 cm long fibers that is better suited for integration with clinical portal imaging and dosimetry systems. The prototype EPID's zero spatial frequency DQE exceeded 3%, more than doubling that measured with the standard EPID (1.25%). This increased DQE was a consequence of using a prototype array detector with a greater equivalent thickness than the combined copper plate and phosphor screen in a standard EPID. The increased thickness of our prototype decreased spatial resolution relative to the standard EPID; however, the prototype EPID NPS was also lower than that measured with the standard EPID across all spatial frequencies. The sensitivity analysis demonstrated that the NPS was strongly affected by the roughness of the boundaries between fiber core and cladding regions. By comparison, the MTF was most sensitive to beam divergence and the presence of air between the fiber array and underlying photodiode panel. Simulations demonstrated that by optimizing these parameters, DQE(0) >4% may be achievable with the proposed next-generation prototype design. The first measurements characterizing the imaging performance of a novel water-equivalent EPID for imaging and dosimetry in radiotherapy demonstrated a DQE(0) more than double that of a standard EPID. MC simulations further demonstrated the potential for developing a next-generation prototype better suited for clinical translation with even higher DQE.

Development of a fast neutron spectrometer based on a plastic fiber array

A three-dimensional position-sensitive fast neutron spectrometer is designed to measure fast neutron spectrum over 10 MeV. The detector consists of a 16 $$\times $$ 16 mutually perpendicular plastic scintillation fiber array coupled to $$2 \times 2$$ Hamamatsu H8500C position-sensitive photomultiplier tubes by optical fibers. The fiber array is fabricated with 0.5 mm $$\times $$ 3 mm fibers and 3-mm square fibers. Due to the combined application of different sizes of fibers, the detector can broaden energy dynamic range and meanwhile have good detection efficiency. The method of the combined application of different sizes of plastic fibers in the array may provide a solution to measure wider energy range of solar neutrons. In this paper, we used FLUKA to simulate the performance of the detector model and report the results of experimental studies with neutrons from a pulsed D-T neutron.