Performance of compact plastic scintillator strips with wavelength shifting fibers using a photomultiplier tube or silicon photomultiplier readout

This study presents the design and performance results for compact plastic scintillator strips using a wavelength shifting fiber(WLS-fiber)readout with dimensions of 0.1 m×0.02 m×2 m.This approach was evaluated as a candidate for a cosmic-ray muon detector for the Taishan Antineutrino Observatory(JUNO-TAO).The strips coupled with 3-inch photomultiplier tubes(PMTs)were measured and compared between the single-end and double-end readout options.Additionally,a strip using the double-end option coupling with a silicon photomultiplier(SiPM)was further evaluated and compared with the results obtained using PMTs.The performance of the strips was determined by a detailed survey along their length with a cosmicray muon after detailed characterization of the 3-inch PMTs and SiPMs.The proposed design employing a compact plastic scintillator strip with WLS-fiber coupling to a SiPM provides a good choice for cosmic-ray muon veto detectors,particularly when detector dimensions must be limited.

Conceptual design of a Cs2LiLaBr6 scintillator‑based neutron total cross section spectrometer on the back‑n beam line at CSNS

To reduce the experimental uncertainty in the 235 U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross section spectrometer(NTOX), a dedicated lithium-containing scintillation detector has been developed on the Back-n beam line at the China Spallation Neutron Source. The Fast Scintillator-based Neutron Total Cross Section(FAST) spectrometer has been designed based on a Cs2Li La Br6(CLLB) scintillator considering the γ-ray flash and neutron environment on the Back-n beam line. The response of the CLLB scintillator to neutrons and γ-rays was evaluated with different 6Li/7 Li abundance ratios using Geant4. The neutron-γdiscrimination performance of the CLLB has been simulated considering different scintillation parameters, physical designs,and light readout modes. A cubic 6Li-enriched( > 90%) CLLB scintillator, which has a thickness of 4-9 mm and side length of no less than 50 mm to cover the Φ 50 mm neutron beam at the spectrometer position, has been proposed coupling to a side readout SiPM array to construct the FAST spectrometer. The developed simulation techniques for neutron-γ discrimination performance could provide technical support for other neutron-induced reaction measurements on the Back-n beam line.

Design optimization of plastic scintillators with wavelength-shifting fibers and silicon photomultiplier readouts in the top veto tracker of the JUNO-TAO experiment

Plastic scintillators(PSs)embedded with wavelength-shifting fibers are widely used in high-energy particle physics,such as in muon taggers,as well as in medical physics and other applications.In this study,a simulation package was built to evaluate the effects of the diameter and layout of optical fibers on the light yield with different configurations.The optimal optical configuration was designed based on simulations and validated using two PS prototypes under certain experimental condi-tions.A top veto tracker(TVT)for the JUNO-TAO experiment,comprising four layers of 160 strips of PS,was designed and evaluated.The threshold was evaluated when the muon tagging efficiency of a PS strip was>99%.The efficiency of three layer out of four layer of TVT is>99%,even with a tagging efficiency of a single strip as low as 97%,using a threshold of 10 photoelectrons and assuming a 40%silicon PM photon detection efficiency.

Data-driven simultaneous vertex and energy reconstruction for large liquid scintillator detectors

High-precision vertex and energy reconstruction are crucial for large liquid scintillator detectors such as that at the Jiangmen Underground Neutrino Observatory(JUNO),especially for the determination of neutrino mass ordering by analyzing the energy spectrum of reactor neutrinos.This paper presents a data-driven method to obtain a more realistic and accurate expected PMT response of positron events in JUNO and develops a simultaneous vertex and energy reconstruction method that combines the charge and time information of PMTs.For the JUNO detector,the impact of the vertex inaccuracy on the energy resolution is approximately 0.6%.

Performance optimization of scintillator neutron detectors for EMD in CSNS

Chinese Spallation Neutron Source(CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the engineering materials diffractometer(EMD) will be installed between 2019–2023. This instrument requires the neutron detectors with the cover area near3 m2in two 90° neutron diffraction angle positions, the neutron detecting efficiency is better than 40%@1A, and the spatial resolution is better than 4 mm×200 mm in horizontal and vertical directions respectively. We have developed a onedimensional position-sensitive neutron detector based on the oblique6Li F/Zn S(Ag) scintillators, wavelength shifting fibers,and Si PMs(silicon photomultipliers) readout. The inhomogeneity of the neutron detection efficiency between each pixel and each detector module, which caused by the inconsistency of the wave-length shifting fibers in collecting scintillation photons, needs to be mitigated before the installation. A performance optimization experiment of the detector modules was carried out on the BL20(beam line 20) of CSNS. Using water sample, the neutron beam with Φ5 mm exit hole was dispersed related evenly into the forward space. According to the neutron counts of each pixel of the detector module, the readout electronics threshold of each pixel is adjusted. Compared with the unadjusted detector module, the inhomogeneity of the detection efficiency for the adjusted one has been improved from 69% to 90%. The test result of the diffraction peak of the standard sample Si showed that the adjusted detector module works well.

Development of an enhanced online tritium monitoring system using plastic scintillation fiber array

Tritium,a radioactive nuclide discharged by nuclear power plants,poses challenges for removal.Continuous online monitoring of tritium in water is crucial for real-time radiation data,given its predominant existence in the environment as water.This paper presents the design,simulation,and development of a tritium monitoring device utilizing a plastic scintillation fiber(PSF)array.Experimental validation confirmed the device’s detection efficiency and minimum detectable activity.The recorded detection efficiency of the device is 1.6×10^(-3),which exceeds the theoretically simulated value of 4×10^(-4)by four times.Without shielding,the device can achieve a minimum detectable activity of 3165 Bq L^(-1)over a 1600-second measurement duration.According to simulation and experimental results,enhancing detection efficiency is possible by increasing the number and length of PSFs and implementing rigorous shielding measures.Additionally,reducing the diameter of PSFs can also improve detection efficiency.The minimum detectable activity of the device can be further reduced using the aforementioned methods.

Development of a scintillating-fiber-based beam monitor for the coherent muon-to-electron transition experiment

The coherent muon-to-electron transition(COMET)experiment is a leading experiment for the coherent conversion of μ^(-)N→e^(-)N using a high-intensity pulsed muon beamline,produced using innovative slow-extraction techniques.Therefore,it is critical to measure the muon beam characteristics.We set up a muon beam monitor(MBM),where scintillating fibers woven in a cross shape were coupled to silicon photomultipliers to measure the spatial profile and timing structure of the extracted muon beam for the COMET.The MBM detector was tested successfully with a proton beamline at the China Spallation Neutron Source and took data with good performance in the commissioning run.The development of the MBM,including its mechanical structure,electronic readout,and beam measurement results,are discussed.

A new method of detecting interferogram in differential phase-contrast imaging system based on special structured x-ray scintillator screen

An x-ray scintillator screen with a special structure, functioning as detector and analyser grating, was proposed for collecting the interferogram of differential phase contrast imaging without absorption grating and difficulty of fabrication by a state of the art technique. On the basis of phase grating diffraction, a detecting model of the scintillator screen was built for analysing the phase and absorption information of objects. According to the analysis, a new method of phase retrievals based on two-images and the optimal structure of screen were presented.

Development of x-ray scintillator functioning also as an analyser grating used in grating-based x-ray differential phase contrast imaging

In order to push the grating-based phase contrast imaging system to be used in hospitM and laboratories, this paper designs and develops a novel structure of x-ray scintillator functioning also as an analyser grating, which has been proposed for grating-based x-ray differential phase contrast imaging. According to this design, the scintillator should have a periodical structure in one dimension with the pitch equaling the period of self-image of the phase grating at the Talbot distance, where one half of the pitch is pixellated and is made of x-ray sensitive fluorescent material, such as CsI（T1）, and the remaining part of the pitch is made of x-ray insensitive material, such as silicon. To realize the design, a deep pore array with a high aspect ratio and specially designed grating pattern are successfully manufactured on 5 inch silicon wafer by the photo-assisted electrochemical etching method. The related other problems, such as oxidation-caused geometrical distortion, the filling of CsI（T1） into deep pores and the removal of inside bubbles, have been overcome. Its pixel size, depth and grating pitch are 3 p.m^7.5 ~m, 150 p^m and 3 Ixm, respectively. The microstructure of the scintillator has been examined microscopically and macroscopically by scanning electron microscope and x-ray resolution chart testing, respectively. The preliminary measurements have shown that the proposed scintillator, also functioning as an analyser grating, has been successfully designed and developed.

Calibration and Unfolding of the Pulse Height Spectra of Liquid Scintillator-Based Neutron Detectors Using Photon Sources

An accurate energy calibration of a 5＂× 2＂ BC501A liquid scintillator-based neutron detector by means of photon sources and the unfolding of pulse height spectra are described. The photon responses were measured with 22Na, 137Cs and 54Mn photon sources and simulated using the GRESP code, which was developed at the Physiknlisch Technische Bundesanstalt in Germany. Pulse height spectra produced by three different photon sources were employed to investigate the effects of the unfolding techniques. It was found that the four unfolding codes of the HEPRO and UMG3.3 packages, including GRAVEL, UNFANA, MIEKE and MAXED, performed well with the test spectra and produced generally consistent results. They could therefore be used to obtain neutron energy spectra in toknmak experiments.

Event vertex and time reconstruction in large-volume liquid scintillator detectors

Large-volume liquid scintillator detectors with ultra-low background levels have been widely used to study neutrino physics and search for dark matter.Event vertex and event time are not only useful for event selection but also essential for the reconstruction of event energy.In this study,four event vertex and event time reconstruction algorithms using charge and time information collected by photomultiplier tubes were analyzed comprehensively.The effects of photomultiplier tube properties were also investigated.The results indicate that the transit time spread is the main effect degrading the vertex reconstruction,while the effect of dark noise is limited.In addition,when the event is close to the detector boundary,the charge information provides better performance for vertex reconstruction than the time information.

Research and Development of Gadolinium Loaded Liquid Scintillator for Daya Bay Neutrino Experiment

Daya Bay reactor anti-neutrino experiment is designed to measure an important parameter, θ13, of neutrino by using anti-neutrino created by Daya Bay and Ling Ao nuclear power plants. The experiment need 200 tonnes gadolinium loaded liquid scintillator (Gd-LS) as target. The purpose of this research is to develop suitable Gd-LS candidates for this experiment, which should have long attenuation length, high light yield, long term stability, and should be compatible with the material used to build the containers. Two kinds of Gd-LS were developed using carboxylic acids 2-ethylhexanoic acid (EHA) and 3, 5, 5-trimethylhexanoic acid (TMHA) as complexing ligands and mesitylene and linear alkyl benzene (LAB) as scintillator solvents. Four Gd-LS samples with different Gd content and complexing ligands were prepared and characterized. The relative light yields and the stabilities of all samples are satisfying, and the values of attenuation length show that TMHA is a better ligand than EHA.

Luminescence Properties of Ce^(3+)∶YAG Single Crystal Scintillator under Vacuum Ultraviolet Excitation

Ce (3+) doped Y_3Al_5O_(12) (Ce (3+)∶YAG) single crystal is an good scintillator due to its excellent thermal,mechanic and scintillant performances. In this paper,its vacuum ultraviolet and fluorescence spectra using the synchrotron radiation as the excitation source was studied. The ultraviolet-visible excitation and absorption spectra of Ce (3+)∶YAG were also measured. The excitation energy transfer process and the luminescent differences under direct excitation into the 5d bands of Ce (3+) and excitation of valence band in Ce (3+)∶YAG scintillator were studied.

Hydrothermal synthesis of Ce: Lu_(2)SiO_(5) scintillator powders

The synthesis of cerium-doped lutetium oxyorthosilicate(LSO)polycrystalline powders was investigated by a hydrothermal proc-ess.The precursor was obtained by the hydrothermal reaction of Lu(NO_(3))_(3)with Na_(2)SiO_(3)at 200℃for 10 h by using urea as precipitator,fol-lowed by a calcination uader proper temperatures.The results of XRD indicated that the precursor was crystallized into A-type LSO phase at 1000℃,and transfetrred to B-type LSO phase when temperature was raised above 1050℃.After being heated at 1250℃for 2 h,single phase of B-type LSO powder was synthesized with homogeneous distribution of particle size ranging from 200 to 300 nm.The photolumi-nescence spectrum of as-synthesized LSO:Ce powders showed a typical broad emission peak centered at 404 nm,corresponding to the 5d^(1)-4f transition of Ce^(3+).

Improvement of machine learning-based vertex reconstruction for large liquid scintillator detectors with multiple types of PMTs

The precise vertex reconstruction for large liquid scintillator detectors is essential.A novel machine learning-based method was successfully developed to reconstruct an event vertex in JUNO.In this study,the performance of machine learning-based vertex reconstruction was further improved by optimizing the input images of neural networks.By separating the information of different types of PMTs and adding the information of the second hit of PMTs,the vertex resolution was improved by approximately 9.4% at 1 MeV and 9.8% at 11 MeV.

Design and preliminary test of tritiated water online detector system based on plastic scintillators

In this study,an online detector system based on plastic scintillators is designed to monitor the activity of tritiated water in the liquid effluents of nuclear power plants.The feasibility of the detector is verified via simulation on Geant4,and the optimal detector structure size is determined.A back-end electronics system is designed and an experimental measurement platform forβ-rays based on a ^(40)KCl solution is constructed.Thirteen ^(40)KC solutions with different activities ranging from 10 to4500 Bq/L are measured,and 1300 V is determined as the optimal operating high voltage of the photomultiplier tubes.A linear fit is performed in 10-min counts,and the maximum linear goodness of fit(R^(2))achieved is 0.9992.Long-term stability measurements are performed for two detectors,one filled with air and the other with a ^(40)KCl solution exhibiting an activity of 2000 Bq/L.The relative deviation of the counts of the detector system every 10 min is 0.998%when the ^(40)KCl solution is used,and the maximum Gaussian R^(2) of the counts is 0.9849.

Efficiency-determined method for thermal neutron detection with inorganic scintillator

Because of 3He shortage,sintillator is a promising alternative choice for neutron detection in the field of thermal neutron scattering and imaging.Also,the neutron detection efficiency is difficult to be determined.In this paper,the efficiency for thermal neutron detection is presented by inorganic scintillator using probability principles,supposed that the material of scintillator is uniform in element distribution,and that attenuation length of scintillation light is longer than that of its thickness in the scintillator.The efficiencies for two pieces of lithium glass are determined by this method,indicating the method is useful for determining efficiency of thermal neutron detections.

A beam range monitor based on scintillator and multi-pixel photon counter arrays for heavy ions therapy

Fast beam range measurements are required to maximize the time available for patient treatment, given that the beam range requires verification with respect to quality assurance to maintain accelerator commissioning standards and ensure patient safety. A novel beam range monitor based on a plastic scintillator and multi-pixel photon counter (MPPC) arrays is therefore proposed in this paper. The monitor was constructed using 128 plastic scintillator films with a thickness of 1 mm and an active area of 50 × 50 mm^(2). A customized MPPC array read the scintillation light of each film. The advantage of dividing the active detector volume into films is that it intercepts the particle beam and enables direct differential light yield measurement in each film, in addition to depth-light curve generation without the need for image analysis A GEANT4 simulation, including scintillator quenching effects, was implemented, and the results revealed that Birks’ law exhibited a slight little influence on the position of the beam range, only changing the shape and absolute normalization of the Bragg curve, which is appropriate for the calculation of the beam range using the depth-light curve. The performance of the monitor was evaluated using a heavy-ion medical machine in Wuwei City, Gansu Province, China. The beam range measurement accuracy of the monitor was 1 mm, and the maximum difference between the measured and reference ranges was less than0.2%, thus indicating that the monitor can meet clinica carbon ion therapy requirements.

Design and development of a plastic scintillator based whole body β/γ contamination monitoring system

Plastic scintillation detectors based whole body β/γ contamination monitors are developed for use in radiation facilities.This microcontroller-based multi-detector system uses 13 plastic scintillator detectors,with minimized dead detection zones,monitoring the whole body,and conforming to the contamination limit prescribed by the regulatory authority.This system has the features for monitoring hands,feet,head,and faceβ/γusing contamination monitors and portal exit monitors.It can detect gamma sources at a dose rate of 10 n Gyh^(-1).The system is calibrated using b sources^(90)Sr/^(90)Y,^(204)Tl,and^(36)Cl,and the efficiency is found to be 29%,22%,and 18%,respectively.Theminimumdetectableβ/γcontaminationis0.15 Bqcm^(-2),which is significantly less than the minimum detection objectives on head,face,hands,and feet.

Geant4 simulation of plastic scintillators for a prototype μSR spectrometer

The experimental muon source on China Spallation Neutron Source(CSNS) is expected to be a high intensity(105μ+/s) surface muon source with a small beam spot of 4-cm diameter.For a practical application of this muon source,we are devoting to develop the first pulsed μSR spectrometer in China.In this paper,the performance of plastic scintillators in the μSR spectrometer is studied by Monte Carlo simulation.The processes such as positron energy deposition,scintillation photons production,light propagation and photon-electron conversion are carefully considered.According to the results,an optimal dimension of the plastic scintillator is proposed using for our future spectrometer,which has a long-strip shape with the dimension variation range of 50–60 mm length,5–8 mm height,and 10–12 mm width.Finally,we can build a spectrometer with a count rate up to 104e+/s by 100–120 forward and backward segmental detectors in total.The simulation could serve as an important guide for spectrometer construction.