Scintillating Fiber Array 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.

A light tracker based on scintillating fibers with SiPM readout

We have developed a novel light tracker based on plastic scintillating fiber arrays readout with Silicon Photomultipliers (SiPMs). The tracker consists of multiple planes, with the fibers in each plane oriented perpendicularly to those in the adjacent plane, in order to allow 3D track reconstruction. The fibers in each plane have round cross sections, with a diameter of 500μm, and are arranged in two staggered layers in a close-packed configuration. The fibers are readout by means of SiPM arrays with a 250μm strip pitch placed at one of their ends. Scintillating fibers allow a reduced material budget while providing a good spatial resolution and a fast response. This design is therefore suitable to track low-energy particles, such as the lowest energy cosmic rays or the electrons produced in Compton scatterings of gamma rays with energies down to 100 keV. We have built a detector prototype, equipped with Hamamatsu 128-channel SiPM arrays, readout with 32-channel PETIROC2A front-end ASICs. These ASICs are controlled by a custom data acquisition system board equipped with Xilinx Kintex-7 FPGA with self-triggering capabilities. The prototype has been tested with particle beams, cosmic rays and radioactive sources. The tracker design will be presented and performance of the prototype will be discussed.

Optical and scintillation properties of Ce:Y3Al5O12 single crystal fibers grown by laser heated pedestal growth method

The single crystal scintillating optical fibers acting as the scintillators and light conductors show potential application in scintillating fiber array detectors with high spatial resolution. In this paper we report the growth of 0.2 at% Ce:Y3Al5O12 single crystal fiber. The crystalline phase, surface morphology of the axial-section and cross-section, optical and scintillation properties of the as-grown fiber were investigated. The Ce:Y3Al5O12 single crystal fiber has a pure YAG phase, a uniform distribution of cerium in the axial-section and cross-section surface. Emission spectrum is composed of broad bands ranging from 440 to 700 nm. In addition, the single crystal fiber has a high light yield of 26115 ± 2000 photons/MeV, low energy resolution of 9.44% @662 keV and decay time of a fast component of 78 ns and a slow component of 301 ns. The intensity ratio of fast to slow components is roughly 8:1.

The GlueX beamline and detector

The GlueX experiment at Jefferson Lab has been designed to study photoproduction reactions with a 9-GeV linearly polarized photon beam. The energy and arrival time of beam photons are tagged using a scintillator hodoscope and a scintillating fiber array. The photon flux is determined using a pair spectrometer, while the linear polarization of the photon beam is determined using a polarimeter based on triplet photoproduction. Charged-particle tracks from interactions in the central target are analyzed in a solenoidal field using a central straw-tube drift chamber and six packages of planar chambers with cathode strips and drift wires. Electromagnetic showers are reconstructed in a cylindrical scintillating fiber calorimeter inside the magnet and a lead-glass array downstream. Charged particle identification is achieved by measuring energy loss in the wire chambers and using the flight time of particles between the target and detectors outside the magnet. The signals from all detectors are recorded with flash ADCs and/or pipeline TDCs into memories allowing trigger decisions with a latency of 3.3 μs. The detector operates routinely at trigger rates of 40 kHz and data rates of 600 megabytes per second. We describe the photon beam, the GlueX detector components, electronics, data-acquisition and monitoring systems, and the performance of the experiment during the first three years of operation.

Spatial resolution of novel liquid scintillating capillary array

Scintillating array image plates are allowed high resolution through a thicker detector which increases quantum efficiency without degrading the imaging resolution substantially. Due to limitations imposed by process capability, scintillator fiber array with pixel diameter less than 0.2 mm is hardly manufactured to improve performance. Therefore, a liquid scintillator capillary array with 0.1 mm pixel is developed to improve the detection efficiency and spatial resolution of image plate for low intensity radiation imaging. Its performances are studied and tested by simulation and experiment, and are compared with those of scintillating fiber array. Especially in order to gain high fidelity representation of modulation transfer function of the array image plate, a method of simulating and measuring the slanted knife edge response and an iterative algorithm are introduced. For 14 MeV neutron and 1.25 MeV gamma, the slanted knife edge responses of these array image plates with pixel dimensions in a range from 0.1 mm to 0.5 mm are respectively simulated by MCNPx program and the modulation transfer function (MTF) are obtained. The simulation results show that compared with scintillating fiber array, the liquid scintillator capillaries array has an obvious merit in spatial resolution because of greater stopping power for secondary charged particle in the capillary quartz glass wall with 0.02 mm in thickness. Its ultimate resolution can reach to 1.8 lp/mm for 14 MeV neutron by simulation. At the 4000 Ci &lt;sup&gt;60&lt;/sup&gt;Co facility, a 5-cm-thick tungsten bar, one side of which has a curvature of 0.1 radian to minimize the misalignment effect, is made a knife edge. The MTF of the scintillating fiber array with 0.3 mm and 0.5 mm pixel and newly developed liquid scintillator capillary array is measured through this tungsten knife edge. Experimental measurement results have also verified that the liquid scintillator capillary array performs well in spatial resolution and luminescent uniformity for 1.25 MeV gamma. The ultimate spatial resolution, 0.9 lp/mm is gained, and those of other scintillating fiber arrays are all less than 0.5 lp/mm. Moreover, experimental test validates the simulating method and simulated results, although the measured value is slight less than the simulated value because of the effect of dimension of &lt;sup&gt;60&lt;/sup&gt;Co source.

Real-Time Monitoring of Gross Beta Radioactivity in Tap Water and Committed Effective Dose.

To achieve real-time monitoring of gross beta radioactivity in drinking water, a scintillating fiber array system was developed. Using this system, the gross beta radioactivity in tap water at Tsinghua University campus in Beijing was monitored, and the same water samples were measured using the evaporation concentration method as a comparison experiment. Finally, the annual committed effective doses to children and adults who drank the tap water for a long time were estimated. The results showed that the gross beta radioactivity in tap water was 0.09 ± 0.03 Bq L using the scintillating fiber array system and 0.076 ± 0.009 Bq L using the evaporation concentration method. The annual committed effective dose values were less than the dose reference level of 0.1 mSv y, as suggested by the World Health Organization. The scintillating fiber array system can be used for measuring gross beta radioactivity in drinking water and protecting public health.

Gross beta determination in drinking water using scintillating fiber array detector

A scintillating fiber array detector for measuring gross beta counting is developed to monitor the real-time radioactivity in drinking water. The detector, placed in a stainless-steel tank, consists of 1096 scintillating fibers, both sides of which are connected to a photomultiplier tube. The detector parameters, including working voltage, background counting rate and stability, are tested, and the detection efficiency is calibrated using standard potassium chloride solution. Water samples are measured with the detector and the results are compared with those by evaporation method. The results show consistency with those by evaporation method. The background counting rate of the detector is 38.131 ± 0.005 cps, and the detection efficiency for β particles is 0.37 ± 0.01 cps/(Bq/l). The MDAC of this system can be less than 1.0 Bq/l for β particles in 120 min without pre-concentration.

Design of readout electronics based on peak-holding circuit and multiplexer for a fast neutron spectrometer

Fast neutron detection is meaningful in many research fields such as space environment monitoring. A scintillating fiber array model for fast neutron detection was proposed and developed in 1980s. Aerospace applications of the model require electronics in small size. To design a dedicated electronic system to readout and process the 384-channel signals from scintillating fiber array, and to use the designed system to fabricate a neutron detector for aerospace applications. With the method of nuclear recoil, fast neutron is detected by tracking recoil proton of n–p scatter in scintillating plastic fibers. Using the peak-holding circuits and multiplexers, the system size and power consumption were reduced. The detector fabricated with the designed system, had 34 cm $$\times $$ 34 cm $$\times $$ 27 cm mechanical size, 20.4 kg weight, and 30.05 W power consumption. Comparing to traditional waveform sampling electronics, the designed electronics was highly integrated and had a small size. The readout electronics also gave a better energy resolution of 39% in neutron detection, while the energy resolution was 43% in previous version. In this study, a highly integrated readout electronic system was designed and verified. The detector using the system gave good performance. The designed electronics had potential development in fast neutron detection and other high energy physics detection system.

A scintillating plastic fiber array and multiplexer based 384-channel fast neutron spectrometer.

A fast neutron detection system based on a scintillating plastic fiber array and multiplexer was designed to measure the spectrum of fast neutrons ranged 10 MeV-100 MeV. With the method of nuclear recoil, the energy of incident neutron was determined by measuring the recoil proton track and deposited energy in scintillating plastic fibers. The detection system was composed of a scintillating plastic fiber array, 6 position sensitive photomultiplier tubes, and a high-density readout electronics based on the multiplexer. The scintillating plastic fiber array was made as a staggered structure with two kinds of fibers in different sizes (0.5 mm-square fiber and 3 mm-square fiber). The structure provided a wider detection energy range and better detection efficiency than arrays made with uniform plastic fibers. A dedicated digital electronics system was well designed to control the whole readout system to provide 384-channel signal processing. The detector had a 48 mm × 48 mm effective detection area and a mechanical size of 34 cm × 34 cm × 27 cm. In the simulation of the detector model performance, the system gave an energy resolution of 23%-35% for neutrons ranged 10 MeV-100 MeV. Experimental results showed that the detector had a good energy linearity and energy resolutions were, respectively, 35.82% at 14.817 MeV, 36.84% at 21.264 MeV, 35.90% at 23.069 MeV, and 32.90% at 24.220 MeV. The optimized prototype model had potential in increasing fast neutron detection performance.

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.

Comparison of polystyrene scintillator fiber array and monolithic polystyrene for neutron imaging and radiography.

The neutron imaging diagnostic at the National Ignition Facility has been operating since 2011 generating neutron images of deuterium-tritium (DT) implosions at peak compression. The current design features a scintillating fiber array, which allows for high imaging resolution to discern small-scale structure within the implosion. In recent years, it has become clear that additional neutron imaging systems need to be constructed in order to provide 3D reconstructions of the DT source and these additional views need to be on a shorter line of sight. As a result, there has been increased effort to identify new image collection techniques that improve upon imaging resolution for these next generation neutron imaging systems, such as monolithic deuterated scintillators. This work details measurements performed at the Weapons Neutron Research Facility at Los Alamos National Laboratory that compares the radiographic abilities of the fiber scintillator with a monolithic scintillator, which may be featured in a future short line of sight neutron imaging systems.

SU‐F‐T‐559: High‐Resolution Scintillating Fiber Array for In‐Vivo Real‐Time SRS and SBRT Patient QA

Purpose:A high‐resolution scintillating fiber detector was built for in‐vivo real‐time patient specific quality assurance (QA). The detector is designed for stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) to monitor treatment delivery and detect real‐time deviations from planned dose to increase patient safety and treatment accuracy.Methods:The detector consists of two high‐density scintillating fiber arrays layered to form an X‐Y grid which can be attached to the accessory tray of a medical linac for SBRT and cone SRS treatment QA. Fiber arrays consist of 128 scintillating fibers embedded within a precision‐machined, high‐transmission polymer substrate with 0.8mm pitch. The fibers are coupled on both ends to high‐sensitivity photodetectors and the output is recorded through a high‐speed analog‐to‐digital converter to capture the linac pulse sequence as treatment delivery progresses. The detector has a software controlled 360 degree rotational system to capture angular beam projections for high‐resolution beam profile reconstruction.Results:The detector was validated using SRS cone sizes from 6mm to 34mm and MLC defined field sizes from 5×5mm2 to 100×100mm2. The detector output response is linear with dose and is dose rate independent. Each field can be reconstructed accurately with a spatial resolution of 0.8mm and the current beam output is displayed every 50msec. Dosimetric errors of 1% with respect to the treatment plan can be identified and clinically significant deviations from the expected treatment can be displayed in real‐time to alert the therapists.Conclusion:The high resolution detector is capable of reconstructing beam profiles in real‐time with submillimeter resolution and 1% dose resolution. This system has the ability to project in‐vivo both spatial and dosimetric errors during SBRT and SRS treatments when only a non‐clinically significant fraction of the intended dose was delivered. The device has the potential to establish new standards for in‐vivo patient specific QA.

Solid polystyrene and deuterated polystyrene light output response to fast neutrons

The Neutron Imaging System has proven to be an important diagnostic in studying DT implosion characteristics at the National Ignition Facility. The current system depends on a polystyrene scintillating fiber array, which detects fusion neutrons born in the DT hotspot as well as neutrons that have scattered to lower energies in the surrounding cold fuel. Increasing neutron yields at NIF, as well as a desire to resolve three-dimensional information about the fuel assembly, have provided the impetus to build and install two additional next-generation neutron imaging systems. We are currently investigating a novel neutron imaging system that will utilize a deuterated polystyrene (CD) fiber array instead of standard hydrogen-based polystyrene (CH). Studies of deuterated xylene or deuterated benzene liquid scintillator show an improvement in imaging resolution by a factor of two [L. Disdier et al., Rev. Sci. Instrum. 75, 2134 (2004)], but also a reduction in light output [V. Bildstein et al., Nucl. Instrum. Methods Phys. Res., Sect. A 729, 188 (2013); M. I. Ojaruega, Ph.D. thesis, University of Michigan, 2009; M. T. Febbraro, Ph.D. thesis, University of Michigan, 2014] as compared to standard plastic. Tests of the relative light output of deuterated polystyrene and standard polystyrene were completed using 14 MeV fusion neutrons generated through implosions of deuterium-tritium filled capsules at the OMEGA laser facility. In addition, we collected data of the relative response of these two scintillators to a wide energy range of neutrons (1-800 MeV) at the Weapons Neutrons Research Facility. Results of these measurements are presented.

Simulation of position-sensitive γ-ray detector based on plastic scintillating fiber array

Simulation of position-sensitive γ-ray detector based on plastic scintillating fiber array

基于塑料闪烁光纤阵列的γ射线位置灵敏探测器数值模拟

基于塑料闪烁光纤阵列的γ射线位置灵敏探测器数值模拟

Plastic fiber scintillator response to fast neutrons.

The Neutron Imaging System at NIF uses an array of plastic scintillator fibers in conjunction with a time-gated imaging system to form an image of the neutron emission from the imploded capsule. By gating on neutrons that have scattered from the 14.1 MeV DT energy to lower energy ranges, an image of the dense, cold fuel around the hotspot is also obtained. An unmoderated spallation neutron beamline at the Weapons Neutron Research facility at Los Alamos was used in conjunction with a time-gated imaging system to measure the yield of a scintillating fiber array over several energy bands ranging from 1 to 15 MeV. The results and comparison to simulation are presented.

Simulation Study of Using High-Z EMA to Suppress Recoil Protons Crosstalk in Scintillating Fiber Array for 14.1 MeV Neutron Imaging

This paper studies the effect of a high-Z extra mural absorber (EMA) to improve the spatial resolution of a plastic (polystyrene) scintillating fiber array for 14.1 MeV fusion neutron imaging. Crosstalk induced by recoil protons was studied, and platinum (Pt) was selected as EMA material, because of its excellent ability to suppress the recoil protons penetrating the fibers. Three common fiber arrays (cylindrical scintillating fibers in square and hexagonal packing arrangements and square scintillating fibers) were simulated using the Monte Carlo method for evaluating the effect of Pt-EMA in improving spatial resolution. It is found that the resolution of the 100 μm square fiber array can be improved from 1.7 to 3.4 lp/mm by using 10- μm-thick Pt-EMA; comparatively, using an array with thinner square fibers (50 μm) only obtains a resolution of 2.1 lp/mm. The packing fraction decreases with the increase of EMA thickness. Our results recommend the use of 10 μm Pt-EMA for the square and the cylindrical (hexagonal packing) scintillating fiber arrays with fibers of 50-200 μm in the cross-sectional dimension. Besides, the dead-zone material should be replaced by high-Z material for the hexagonal packing cylindrical fiber array with fibers of 50-200 μm in diameter. Tungsten (W) and gold (Au) are also used as EMA in the three fiber arrays as a comparison. The simulation results show that W can be used at a lower cost, and Au does not have any advantages in cost and resolution improvement.

A Real-time Scintillating Fiber Detector to Improve Patient Safety in External Beam Radiation Therapy

The purpose of this study is to improve patient safety in radiation oncology by implementing real time verification of fluence delivered during external beam radiation therapy using a radiation hard scintillating fiber sensor array architecture and real time data acquisition hardware. Radiation oncology patients undergo highly complicated treatment procedures in which delivered dose should be controlled, recorded, and verified for quality and safety. Currently, radiation treatment cumulative dose is measured prior to delivery, which is not sensitive to temporal variations that could occur during imaging or treatment. Therefore, the actual quality and safety of the radiation therapy procedure is unknown and any deviation from the intended dose cannot be identified, thus cannot be corrected. To address this gap in patient safety, we developed scintillating fiber array sensors with real time data acquisition hardware to implement real time fluence verification of photon and electron beams. These on line detectors can operate on a wide range of clinical devices through modification of sensor element geometry and front end electronics operating parameters. This common technological platform provides a simplified method to construct low cost radiation based modality specific dosimeters. As an example, we developed and tested a scintillating fiber array for linac external beam radiation therapy with plastic encapsulated scintillating fibers and photodetectors integrated in a monolithic configuration. This detector has high speed front end amplifiers for real time acquisition and verification of the pulsed linac output during treatment. We determined the detector sensitivity and linearity response with respect to beam intensity and field size for the clinical range of photon beam energies. The scintillating fiber spatial detection sensitivity is 2.3 mV/mm with a statistical error of 0.5 mV. Fiber linearity response with respect to beam intensity and field size was within 2% for all tested beams. The front end amplifiers have a time response of 250 nsec. The fiber dosimeter has a maximum beam attenuation of 2.4% and is used in an online transmission configuration for in vivo treatment delivery accuracy monitoring. The development of this technology addresses the urgent need for in vivo real time quality assurance of external beam therapy to increase patient safety. The developed linear fiber array has high spatial and temporal resolution to provide accurate dose verification, thus providing therapists real time feedback of external beam treatment fluence with minimum beam attenuation to increase patient safety. Configurations for other external beam treatment devices such as tomotherapy machines could be done with little design modification.

WE‐G‐BRB‐06: Real‐Time Radiation Field Tracking Using Long Scintillating Fibers

To ensure the quality assurance of small field, dynamic radiotherapy, we present and validate a radiation tracking system based on long scintillating fibers that allows for the real-time measurement of the position and energetic fluence of a small incident radiation field. We aligned 60 parallel scintillating fibers on a thin grooved acrylic slab with a 100-cm source-to-fibers distance. Both ends of each scintillating fiber were coupled to clear optical fibers to enable light collection by a single CCD camera using an f/0.95, 50 mm focal length lens. Using a small, static photon radiation field of 2×2 cm2 of a Varian Clinac iX, we changed the interaction position on the prototype using the linac treatment couch. The interaction position parallel and perpendicular to the scintillating fiber array were deduced using the optical attenuation of the scintillating fibers. The energetic fluence of the incident field was calculated from the fibers light fluxes, corrected for the position dependent optical attenuation and scintillation efficiency. Considering a treatment couch positioning error of ±0.5 mm, the system was able to measure the field position with a mean error of 0.1 mm perpendicular and 0.8 mm parallel to the scintillating fiber array. The maximum error measured using this setup was of 0.13 mm perpendicular and 3.2 mm parallel to the scintillating fiber array. The energetic fluence was determined with a mean error of 0.5% and a maximum error of 2.2%. This work demonstrates the capacity of a long scintillating fibers array to detect in real-time both the position and the energetic fluence of an incident small radiation field. Such methodology would allow for the real-time tracking of small field in both photon and particle radiation therapy.

SU-E-T-147: Scintillating Fiber Array to Determine the Proton Beam Range

Purpose: To develop the scintillating fiber array dosimeter to determine the proton beam range for the purpose of quality assurance of the patient in the proton therapy. Methods: A scintillating fiber dosimeter was composed of a commercial scintillating fiber optically coupled with organic based optical fiber. An array of scintillating fibers was settled inside a water bath. The scintillating light was amplified by photo multiplier tube before being gathered by commercial data acquisition system. Bragg peak and SOBP was measured with scintillating fiber dosimetry. The correction of the signal between the dosimeters and quenching effect of each dosimeter itself were conducted in home-made software. The results were compared with the ion chamber.Results: The signals from each scintillating fiber dosimeter showed randomly distributed along the depth. After calibrating between the dosimeters, the signals showed similar curve to Bragg peak and SOBP. Then correcting the quenching effect made the signal to coincident with the icon chamber results Conclusions: We improved the scintillating fiber optic dosimetry system which is previously developed in scanning type to the array type. The developed dosimetry system can provided more applicable and faster way to determine the proton beam range.