Wavelength-shifting Fibers Research Articles

Characterization of a radiation detector based on opaque water-based liquid scintillator

We present the characterization of a novel radiation detector based on an opaque water-based liquid scintillator. Opaque scintillators, also known as LiquidO, are made to be highly scattering, such that the scintillation light is effectively confined, and read out through wavelength-shifting fibers. The 1-liter, 32-channel prototype demonstrates the capability for both spectroscopy and topological reconstruction of point-like events. The design, construction, and evaluation of the detector are described, including modeling of the scintillation liquid optical properties and the detector’s response to gamma rays of several energies. A mean position reconstruction error of 4.4 mm for 1.6 MeV-equivalent events and 7.4 mm for 0.8 MeV-equivalent events is demonstrated using a simple reconstruction approach analogous to center-of-mass.

An Imaging Calorimeter prototype with WLS fibers and LYSO crystal

We propose an innovative detector for the new generation of satellite-borne experiments for sub-GeV gamma rays. It consist of a modular structure, exploiting wavelength shifting fibers (WLS) coupled to a thin scintillator crystal and readout by Silicon Photomultipliers (SiPMs). This type of detector could be used for scientific applications, in the detection of astrophysical gamma rays. A first module prototype was assembled and it was tested in our laboratories in several configurations with a 90Sr radioactive source and cosmic rays (CRs) at ground, to carry out a study of light yield. Preliminary results will be presented in this contribution.

Performance Simulation of Muon Detectors Based on Structural Design and Array Layout of Plastic Scintillators

The performances of muon detectors have prominent effects on the accuracy and application scenario of muon imaging. Previous studies have paid more attention to the performance improvements of muon detectors in the assembly of imaging systems and optimization of imaging algorithms, while, the structural design and array layout of plastic scintillators in muon detectors have received less attention. In this work, the simulation models of plastic scintillator, wavelength-shifting (WLS) fibers, and muon source are constructed in the Geant4 software. On this basis, different factors affecting light collection efficiency (LCE) have been investigated, including muon hitting position, plastic scintillator cross-sectional shape and size, and WLS fiber size and position. Meanwhile, the influences of scintillator array layout, average width, and muon energy on the position resolution performance of the detector are investigated. The constructive results have been listed as follows: (a) the longitudinal length of the plastic scintillator unit, the shape and size of the WLS fiber, and the position of the WLS fiber have a large impact on the LCE. (b) The Right-angled triangle staggered layout is suitable for small-sized scintillators with single-energy muon hitting, and the Rhombus staggered layout is suitable for large-sized scintillators with multiple-energy muon hitting. This work provides theoretical support for the structural design and array layout of plastic Scintillators, and it has an important significance as a guide for the design of the subsequent muography system.

Expected performance of Cosmic Muon Veto Detector

The India-based Neutrino Observatory (INO) collaboration has established a miniICAL detector, at the transit campus of IICHEP, Madurai, India, which serves as a prototype detector of the larger Iron-Calorimeter detector (ICAL). The purpose of miniICAL lies in unraveling the intricate physics and engineering challenges inherent in constructing and operating a substantial ICAL-type detector. To explore the feasibility of building a large-scale neutrino experiment at shallow depths the collaboration has embarked upon the construction of a Cosmic Muon Veto Detector (CMVD) around the miniICAL detector. The primary objective of this endeavor revolves around attaining a veto efficiency surpassing 99.99%, while simultaneously maintaining a false-positive rate lower than 10-5. The CMVD system is based on extruded plastic scintillators (EPS) and utilizes wavelength-shifting fibers to collect scintillation photons and uses silicon photomultipliers (SiPMs) as photo-transducers. A software tool is developed for CMVD and is integrated with the existing miniICAL consisting of RPC detectors. The simulation is tuned to include properties of EPSs and WLS fibers, measured efficiencies, and time resolutions of EPSs. Measured spectra and noise in SiPMs are also taken into account. The muon tracks in the RPCs are used to estimate the muon veto efficiency of CMVD to arrive at efficient muon veto criteria. With improved veto efficiency of cosmic muons, the CMVD experiment will help to pave the way for future large-scale shallow-depth neutrino experiments e.g. INO-type experiments, enhancing our understanding of neutrino properties.

Design and test for the CEPC muon subdetector based on extruded scintillator and SiPM

The integration of a scintillator, wavelength-shifting fiber, and silicon photomultiplier (SiPM) has demonstrated superior performance in the K-long and Muon detector (KLM) of the Belle II experiment. This study outlines our research and development (R&D) initiatives aimed at harnessing similar detection technologies, incorporating a novel scintillator and SiPM, for potential use in a muon detector for the proposed Circular Electron Positron Collider (CEPC) experiment. Our R&D activities have been focused on evaluating the efficacy of a newly developed 150 cm-long scintillator, alongside the NDL SiPM featuring a sensitive area of 3 mm×3 mm, or the Hamamatsu MPPC with a 1.3 mm× 1.3 mm sensitive surface. The project also includes the fabrication of a detector strip and the implementation of techniques designed to optimize light collection efficiency. Cosmic ray testing has shown that both NDL SiPMs and MPPCs are capable of highly efficient photon collection, achieving efficiencies significantly exceeding 90% when employing a threshold of 8 photoelectrons. Additionally, the time resolution for detecting events at the distant end of a scintillator strip has been measured to be better than 1.7 ns. The remarkable performance observed lays the foundation for advancing R&D including prototype modules aiming for reference Technical Design Report of CEPC detector recently.

Novel high-efficiency 2D position-sensitive ZnS:Ag/6LiF scintillator detector for neutron diffraction

Scintillator-based ZnS:Ag/6LiF neutron detectors have been under development at ISIS for more than three decades. Continuous research and development aim to improve detector capabilities, achieve better performance and meet the increasingly demanding requirements set by neutron instruments. As part of this program, a high-efficiency 2D position-sensitive scintillator detector with wavelength-shifting fibres has been developed for neutron-diffraction applications. The detector consists of a double scintillator-fibre layer to improve detection efficiency. Each layer is made up of two orthogonal fibre planes placed between two ZnS:Ag/6LiF scintillator screens. Thin reflective foils are attached to the front and back scintillators of each layer to minimize light cross-talk between layers. The detector has an active area of 192 × 192 mm with a square pixel size of 3 × 3 mm. As part of the development process of the double-layer detector, a single-layer detector was built, together with a prototype detector in which the two layers of the detector could be read out separately. Efficiency calculations and measurements of all three detectors are discussed. The novel double-layer detector has been installed and tested on the SXD diffractometer at ISIS. The detector performance is compared with the current scintillator detectors employed on SXD by studying reference crystal samples. More than a factor of 3 improvement in efficiency is achieved with the double-layer wavelength-shifting-fibre detector. Software routines for further optimizations in spatial resolution and uniformity of response have been implemented and tested for 2D detectors. The methods and results are discussed in this manuscript.

Arduino-Based Readout Electronics for Nuclear and Particle Physics.

Open Hardware-based microcontrollers, especially the Arduino platform, have become a comparably easy-to-use tool for rapid prototyping and implementing creative solutions. Such devices in combination with dedicated front-end electronics can offer low-cost alternatives for student projects, slow control and independently operating small-scale instrumentation. The capabilities can be extended to data taking and signal analysis at mid-level rates. Two detector realizations are presented, which cover the readouts of proportional counter tubes and of scintillators or wavelength-shifting fibers with silicon photomultipliers (SiPMs). The SiPMTrigger realizes a small-scale design for coincidence readout of SiPMs as a trigger or veto detector. It consists of a custom mixed signal front-end board featuring signal amplification, discrimination and a coincidence unit for rates of up to 200 kHz. The nCatcher transforms an Arduino Nano to a proportional counter readout with pulse shape analysis: time over threshold measurement and a 10-bit analog-to-digital converter for pulse heights. The device is suitable for low-to-medium-rate environments up to 5 kHz, where a good signal-to-noise ratio is crucial. We showcase the monitoring of thermal neutrons. For data taking and slow control, a logger board is presented that features an SD card and GSM/LoRa interface.

An optimization design for fiber-optic neutron detector based on 6LiF/ZnO:Ga and wavelength shifting fibers

The fiber-optic neutron detector consists principally of a neutron-sensitive scintillator, optical fiber, and photomultiplier tube. It has features such as small size, real-time online measurement capability, and high resistance to electromagnetic interference. This detector is excellent for neutron detection in areas with limited space and strong electromagnetic interference. However, its small size results in a comparatively low neutron sensitivity. The goal of this study is to look into the relationship between detector parameters and performance in order to improve the detector design. The research begins with the development of a detector model using Monte Carlo simulation programs to investigate the relationship between the 6LiF/ZnO:Ga mass ratio, thickness, wavelength-shifting fiber length, and detector performance. The 6LiF/ZnO:Ga mass ratio was then used as the test parameter to create equivalent detector samples for experimental validation. The results show that the detector has the highest neutron sensitivity when the mass ratio of 6LiF/ZnO:Ga is 1:1. This pattern is consistent with theoretical simulation results, indicating that the optimization strategy for detector parameters is feasible. The results of this work give a theoretical foundation for the development and practical implementation of the fiber-optic neutron detector.

Design of high-light-collection-efficiency optical fiber for germanium detectors immersed in liquid argon

The implementation of Slicon Photon-Multipliers (SiPMs) wave-length shifting (WLS) fibers light response system in liquid argon (LAr) is a promising technology for suppressing background in rare event experiments. Moreover, it is particularly relevant for experiments that utilize high-purity germanium (HPGe) detectors directly operated in LAr, such as the direct detection of dark matter and neutrinoless double beta decay. In this work, we exhibit a designed WLS fiber for the LAr detector, verify the feasibility of the manufacturing technology, and simulation research about its light collection performance. The novel fiber incorporates two materials, styrene and 1,1,4,4-tetraphenyl-1,3-butadiene (TPB). The pre-experiments proved that the fiber has good WLS and light-conducting properties for ultraviolet light. In addition, the effect of different light collection methods on detection efficiency was assessed by Geant4 simulation. Our results show that adding optical fibers can significantly increase light collection efficiency. Compared with the design of TPB coating with commercial fiber, the new structure of WLS fiber can improve the light collection efficiency by 50%. The simulation results indicate that the new fiber structure can enhance the light collection efficiency of the LAr detection system, thereby improving the anti-coincidence system's performance in rare event experiments.

Performance of New Kuraray Wavelength-shifting Fibers with Short Decay Time

Abstract We measure the decay time and the attenuation length of newly developed wavelength-shifting fibers, the YS series, from Kuraray, which have a fast response. Using a 405 nm laser, the decay times of YS-2, 4, and 6 are measured to be 3.64 ± 0.04, 2.15 ± 0.03, and 1.47 ± 0.02 ns, respectively, for a light injection distance of 10 cm. The decay time of Y-11 is measured to be 7.10 ± 0.09 ns using the same system. All fibers are found to have similar attenuation lengths of more than 4 m. When combined with the plastic scintillators EJ-200 and EJ-204, the YS series has better time resolution than Y-11, with light yields of 60–100% of Y-11.

Characterisation of plastic scintillator paddles and lightweight MWPCs for the MID subsystem of ALICE 3

The ALICE collaboration is proposing a completely new detector, ALICE 3, for operation during the LHC Runs 5 and 6. One of the ALICE 3 subsystems is the Muon IDentifier detector (MID), which has to be optimised to be efficient for the reconstruction of J/ψ at rest (muons down to p T ≈ 1.5 GeV/c) for |η| < 1.3. Given the modest particle flux expected in the MID of a few Hz/cm2, technologies like plastic scintillator bars (≈ 1 m length) equipped with wavelength-shifting fibers and silicon photomultiplier readout, and lightweight Multi-Wire Proportional Chambers (MWPCs) are under investigation. To this end, different plastic scintillator paddles and MWPCs were studied at the CERN T10 test beam facility. This paper reports on the performance of the scintillator prototypes tested at different beam momenta (from 0.5 GeV/c up to 6 GeV/c) and positions (horizontal, vertical, and angular scans). The MWPCs were tested at different momenta (from 0.5 GeV/c to 10 GeV/c) and beam intensities, their efficiency and position resolutions were verified beyond the particle rates expected with the MID in ALICE 3.

Study of polysterene based scintillator ageing in the DANSS experiment

DANSS is a spectrometer for reactor antineutrinos based on plastic scintillator. The sensitive volume of the detector is made of 2500 polystyrene based scintillator plates with wavelength shifting (WLS) fiber readout (strips). We present a study of the light yield of strips during 6.5 years of DANSS continuous running. Overall ageing at the rate 0.55 ± 0.05 (syst.) % per year is observed that is considerably smaller than in other similar experiments. We also observe the WLS fiber attenuation length shortening at the rate 0.26 ± 0.04(stat.) % per year.

Towards a fiber barrel detector for next-generation high-pressure gaseous xenon TPCs

The NEXT (Neutrino Experiment with a Xenon TPC) project is an international collaboration aimed at finding evidence of neutrinoless double beta decay using gaseous xenon. The current phase of the project involves the construction and operation of NEXT-100, which is designed to hold 100 kg of xenon at 15 bar and is expected to start commissioning in the first quarter of 2024. NEXT-HD will be a tonne scale experiment following NEXT-100 and will incorporate a symmetric design, with one cathode and two anodes. For this detector, the collaboration is considering to implement a barrel of wavelength-shifting fibers read-out by silicon photomultipliers to measure the energy of the particles interacting in the gaseous xenon. In this document, we will discuss the characteristics of this approach and provide an update on the related R&D efforts.

Electronics design for a muon imaging system using triangular plastic scintillators with WLS fiber readouts

Muon imaging technology has developed rapidly over the past decades with extensive applications. In many cases, plastic scintillator detectors are preferred because of their high cost performance, ease of processing and robustness in harsh environments. To reduce imaging time and improve imaging quality, detectors tend to have large areas and high position resolutions. The challenge to the electronics for such detectors is to maintain the scale of electronics acceptable while improving the high position resolution of the detector. In this paper, the basic detector unit is a triangular strip of plastic scintillator, each embedded with two wavelength-shifting (WLS) fibers read out by the silicon photomultipliers (SiPMs). Since the hit position of muon on the detector is determined by the splitting ratio of the scintillation light on two adjacent scintillator strips, it is necessary the readout electronics has high linearity and low noise. The possibility of the electronics channel multiplexing on the same detector plane is fully explored so that four WLS fibers can be read out by one SiPM realizing 2:1 readout channel compression. Furthermore, since multiple electronics modules are connected by a daisy chain structure, the electronics system is very scalable with its data acquisition system (DAQ) independent of detector size. In addition to detailing the position encoding readout scheme, the design of electronics module and the DAQ system, the electronics system has been implemented and applied to a prototype detector for performance evaluation. Using scintillator strips with 11 mm pitch size, the position resolution of the detector reaches 1.49 mm, which demonstrates that the designed electronics is suitable for the new detector structure, and the combination of the two has a good application prospect in muon imaging.

A Long-Term Stability Study of Counters Consisting of Extruded-Scintillator Strips and Wavelength-Shifting Fibers

A Long-Term Stability Study of Counters Consisting of Extruded-Scintillator Strips and Wavelength-Shifting Fibers

Double Photodiode Readout System for the Calorimeter of the HERD Experiment: Challenges and New Horizons in Technology for the Direct Detection of High-Energy Cosmic Rays

The HERD experiment is a future experiment for the direct detection of high-energy cosmic rays and is to be installed on the Chinese space station in 2027. The main objectives of HERD are the first direct measurement of the knee of the cosmic ray spectrum, the extension of electron+positron flux measurement up to tens of TeV, gamma ray astronomy, and the search for indirect signals of dark matter. The main component of the HERD detector is an innovative calorimeter composed of about 7500 LYSO scintillating crystals assembled in a spherical shape. Two independent readout systems of the LYSO scintillation light will be installed on each crystal: the wavelength-shifting fibers system developed by IHEP and the double photodiode readout system developed by INFN and CIEMAT. In order to measure protons in the cosmic ray knee region, we must be able to measure energy release of about 250 TeV in a single crystal. In addition, in order to calibrate the system, we need to measure typical releases of minimum ionizing particles that are about 30 MeV. Thus, the readout systems should have a dynamic range of about 107. In this article, we analyze the development and the performance of the double photodiode readout system. In particular, we show the performance of a prototype readout by the double photodiode system for electromagnetic showers as measured during a beam test carried out at the CERN SPS in October 2021 with high-energy electron beams.

Optimization of WLS fiber readout for the HERD calorimeter

A novel 3-D calorimeter, composed of about 7500 LYSO cubes, is the key and crucial detector of the High Energy cosmic-Radiation Detection (HERD) facility to be installed onboard the China Space Station. Energy deposition from cosmic ray in each LYSO cube is translated by multiple wavelength shifting (WLS) fibers for multi-range data acquisition and real-time triggering.In this study, various methods of surface finish and encapsulation of the LYSO cube were investigated to optimize the amplitude from the WLS fiber end with the aim of improving the signal-to-noise ratio of Intensified scientific CMOS (IsCMOS) collection. The LYSO cube with five rough surfaces and a specular reflector achieves the maximum amplitude at the low-range fiber end, which is increased by roughly 44% compared to the polished cube with PTFE wrapping.The non-uniformity of amplitude at different positions on the LYSO cube surface was measured by X-ray and the positional correlation factor was derived for the entire cube. A simulation based on HERD CALO was conducted, which revealed that both the LYSO cube with five rough surfaces and the cube with rough bottom face exhibit superior energy resolution for electrons compared to the other two configurations.

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

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

Cherenkov Glass Detectors with Wavelength Shifting Fibers for Neutron Measurements

Two groups of Cherenkov glass detectors, containing six samples in total, have been produced in our laboratory with different compositions and configurations. The first group included three samples that were made of SiO2, and the other group contained three samples that were made of PbO+SiO2. All the samples were tested by using a PuBe source. Wavelength shifting (WLS) fibers were implemented in four samples (two from each group) to improve the light output of the Cherenkov detectors. Even though Cherenkov detectors have low noise due to the low-energy threshold and short decay constant (on the order of picoseconds), their light yield is low. A few hundred Cherenkov photons can be generated per mega-electron-volt. Without the WLS materials, most Cherenkov photons are likely to be absorbed within the glass sample before they can reach the photon sensor. WLS fibers do not directly increase the number of Cherenkov photons, but they can reduce the energy of Cherenkov photons and direct them toward the photon sensor. This photon energy reduction helps increase the efficiency of light collection and improves matching between photon wavelength and photon detector quantum efficiency. The objective of this work is to test Cherenkov glass detectors for the detection of neutrons by placing a 1-mm layer of Gd2O3 in front of the detectors. The focus is to increase the output light by observing the effect of the WLS fibers on the detection process with the use of different composition samples. The light output of the Cherenkov detectors was expected to increase more in the lead group than in the silicon group. Most of the Cherenkov energies are likely to be deposited within the glass sample. The approach is to direct the WLS photons to the photon sensor by allowing the energy deposition that takes place in the WLS fibers. A detailed model by Geant4 confirmed that the measured observations were reasonable. Both experimental and simulated results show an increase in light output when WLS fibers are added to the detectors.

Silicon photomultiplier based scintillator thermal neutron detector for China Spallation Neutron Source (CSNS)

The energy-resolved neutron imaging spectrometer (ERNI) will be installed in 2022 according to the spectrometer construction plan of the China Spallation Neutron Source (CSNS). The instrument requires neutron detectors with the coverage area of approximately 4 m2 in 5°–170° neutron diffraction angle. The neutron detection efficiency needs to be better than 40% at 1 Å neutron wavelength. The spatial resolution should be better than 3 mm × 50 mm in the horizontal and vertical directions respectively. We develop a one-dimensional scintillator neutron detector which is composed of the 6LiF/ZnS (Ag) scintillation screens, the wavelength-shifting fiber (WLSF) array, the silicon photomultipliers (SiPMs), and the self-designed application-specific integrated circuit (ASIC) readout electronics. The pixel size of the detector is designed as 3 mm × 50 mm, and the neutron-sensitive area is 50 mm × 200 mm. The performance of the detector prototype is measured using neutron beam 20# of the CSNS. The maximum counting rate of 247 kHz, and the detection efficiency of 63% at 1.59 Å are obtained. The test results show that the performance of the detector fulfills the physical requirements of the ERNI under construction at the CSNS.