Wavelength Shifting Fiber Readout Research Articles

LSO/LYSO Crystals for Calorimeters in Future HEP Experiments

Because of their high stopping power (X 0 = 1.14 cm), fast (τ = 40 ns) bright (4 times BGO) scintillation with small temperature coefficient (−0.2%/°C) and superb radiation hardness, LSO/LYSO crystals are chosen to construct electromagnetic calorimeters (ECAL) of total absorption nature. One critical issue for this application is the light response uniformity (LRU) of long crystal bars with tapered geometry, which is affected by the non-uniform light yield along the crystal, the self-absorption and the optical focusing effect. Following a ray-tracing simulation study, an uniformization method was developed by roughening one side surface with LRU of better than 3% achieved. LSO/LYSO crystals are also proposed as the active material for a sampling ECAL for future HEP experiments in severe radiation environment. Preliminary designs with Pb or W absorber are described. Measurements of light collection efficiency (LCE) for prototype Shashlik cells with wavelength shifting fiber readout are presented. Future development on LSO/LYSO crystal based sampling ECAL is discussed.

A scintillator-based detector with sub-100-μm spatial resolution comprising a fibre-optic taper with wavelength-shifting fibre readout for time-of-flight neutron imaging

A scintillator-based neutron-counting imaging detector with a sub-100-μm spatial resolution was developed for energy-selective neutron imaging. The detector head of the detector comprised a thin ZnS/6LiF scintillator screen, a fibre-optic taper and crossed wavelength-shifting (WLS) fibre arrays. A high spatial resolution was achieved by constructing the scintillator with a thickness of 100μm and placing it in contact with the fibre-optic taper at a magnification ratio of 3.1:1. WLS fibres with a diameter of 100±5μm (mean±SD) were specially made, and their dye content was optimized for use in crossed WLS-fibre arrays. The developed detector had a pixel size of 34μm×34μm, and exhibited spatial FWHM resolutions of 80±7μm and 61±6μm in the x and y directions, respectively. A small prototype detector demonstrated the capability of neutron imaging using Bragg edges of a Cu/Fe sample when using the pulsed-neutron source in the Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex.

A large-area two-dimensional scintillator detector with a wavelength-shifting fibre readout for a time-of-flight single-crystal neutron diffractometer

A two-dimensional scintillator-based neutron detector that has a neutron-sensitive area of 256×256mm2 with a pixel size of 4mm was developed. The detector was designed to be compact and modular with the smallest dead area for the SENJU time-of-flight Laue single-crystal diffractometer to be constructed in the Materials and Life Science Experimental Facility at the Japanese Proton Accelerator Research Complex. The detector employed wavelength-shifting (WLS) fibres to collect scintillation light generated in a neutron-sensitive scintillator. The 64 WLS fibres with a diameter of 1mm were regularly spaced at a pitch of 4mm both in the x and y directions to produce a detector with a large neutron-sensitive area and a small number of electronics channels. Two ZnS/10B2O3 scintillator screens with an optimised scintillator thickness sandwiched the cross-arranged WLS fibre arrays to ensure a high detection efficiency for thermal neutrons. The prototype detector exhibited a detector efficiency of 40±1%(mean±SD) for 1.6Å neutrons and a 60Co gamma-ray sensitivity of 6.0±0.1×10−6, which fulfilled the required detector specifications for SENJU.

A half-millimetre spatial resolution fibre-coded linear position-sensitive scintillator detector with wavelength-shifting fibre read-out for neutron detection

A fibre-coded linear scintillator detector with a half-millimetre spatial resolution was developed with wavelength-shifting fibre read-out for neutron detection. The head of the detector comprised a ZnS/6LiF scintillator placed on the ribbon of wavelength-shifting (WLS) fibres. Both ends of the fibres were coded to reduce the number of read-out photomultipliers and associated electronic circuitry. The prototype detector in which the fibre ribbon was sandwiched between two ZnS/6LiF scintillators exhibited a spatial resolution of 0.5mm, a detection efficiency of 35% for 1-Å neutrons, and a gamma sensitivity of less than 10−7. This type of detector would be useful where a submillimetre spatial resolution is required with large detector coverage such as in neutron reflectometers.

Monte-Carlo simulation of a compact gamma-ray detector using wavelength-shifting fibers coupled to a YAP scintillation crystal**Supported by National Nature Science Foundation of China (10275063)

The production and transportation of fluorescent light produced in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal is simulated using the GEANT4 codes. An advantage of the wavelength-shifting fiber readout technique over a direct readout with a position-sensitive photo-sensor is the reduced requirement for position sensitive photomultiplier tube photocathode area. With this gamma-ray detector, the gamma camera is small and flexible and has larger effective field of view and low cost. Simulation results show that a) a mean 12 of photons per 59.5 keV gamma ray interaction is produced in the WSF located nearest to the incident gamma ray, and a spatial resolution of 3.6 mm FWHM is obtained, b) a mean 27 of photons per 140 keV gamma ray interaction is produced and a spatial resolution of 3.1 mm FWHM is obtained. Results demonstrate the feasibility of this concept of a compact gamma-ray detector based on wavelength-shifting fibers readout. However, since the very low photoelectron levels, it is very important to use a photon counting device with good single photo-electron response to readout the WSFs.

High efficiency plastic scintillator detector with wavelength-shifting fiber readout for the GLAST Large Area Telescope

This paper describes the design and performance studies of the scintillator tile detectors for the anti-coincidence detector (ACD) of the Large Area Telescope (LAT) on the Gamma ray Large Area Space Telescope (GLAST), scheduled for launch in early 2008. The scintillator tile detectors utilize wavelength-shifting fibers and have dual-photomultiplier-tube readout. The design requires highly efficient and uniform detection of singly charged relativistic particles over the tile area and must meet all requirements for a launch, as well as operation in a space environment. We present here the design of three basic types of tiles used in the ACD, ranging in size from ∼450 to ∼2500 cm 2, all ∼1 cm thick, with different shapes, and with photoelectron yield of ∼20 photoelectrons per minimum ionizing particle at normal tile incidence, uniform over the tile area. Some tiles require flexible clear fiber cables up to 1.5 m long to deliver scintillator light to remotely located photomultiplier tubes.

Development of cosmic-ray tracker for KASKA neutrino oscillation experiment

A cosmic-ray tracking system to trace the cosmic muon passage will be installed in the detector for the planned reactor-neutrino oscillation experiment KASKA. Background events due to isotopes produced in the spallation reaction by the cosmic muons can be estimated by their association to the cosmic-ray track. For this detector, we propose a scheme of a cosmic-ray tracker consisting of extruded plastic scintillators with wavelength-shifting fiber readout. It aims at an improvement of position uniformity, detection efficiency, and detection accuracy by using the time difference between both sides of scintillator bar. Some basic performances of prototype detector were measured by beam test at the 12-GeV Proton Synchrotron in High Energy Accelerator Research Organization (KEK).

A large acceptance scintillator detector with wavelength shifting fibre readout for search of [formula omitted]-nucleus bound states

A large acceptance scintillator detector with wavelength shifting optical fibre readout has been designed and built to detect the decay particles of η -nucleus bound system (the so-called η -mesic nuclei), namely, protons and pions. The detector, named as ENSTAR detector, consists of 122 pieces of plastic scintillator of various shapes and sizes, which are arranged in a cylindrical geometry to provide particle identification, energy loss and coarse position information for these particles. A solid angle coverage of ∼ 95 % of total 4 π is obtained in the present design of the detector. Monte Carlo phase space calculations performed to simulate the formation and decay of η -mesic nuclei suggest that its decay particles, the protons and pions are emitted with an opening angle of 150 ± 20 ∘ , and with energies in the range of 25–300 and 225–450 MeV, respectively. The detailed GEANT simulations show that ∼ 80 % of the decay particles (protons and pions) can be detected within ENSTAR. Several test measurements using alpha source, cosmic-ray muons, etc. have been carried out to study the response of ENSTAR scintillator pieces. The in-beam tests of fully assembled detector with proton beam of momentum 870 MeV / c from the Cooler synchrotron COSY have been performed. The test results show that the scintillator fibre design chosen for the detector has performed satisfactorily well. The present article describes the detector design, simulation studies, construction details and test results.

The anti-coincidence detector for the GLAST large area telescope

This paper describes the design, fabrication and testing of the Anti-Coincidence Detector (ACD) for the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT). The ACD is LATs first-level defense against the charged cosmic ray background that outnumbers the gamma rays by 3–5 orders of magnitude. The ACD covers the top and four sides of the LAT tracking detector, requiring a total active area of ∼8.3 m 2. The ACD detector utilizes plastic scintillator tiles with wavelength shifting fiber readout. In order to suppress self-veto by shower particles at high gamma-ray energies, the ACD is segmented into 89 tiles of different sizes. The overall ACD efficiency for detection of singly charged relativistic particles entering the tracking detector from the top or sides of the LAT exceeds the required 0.9997.

High-position-resolution neutron imaging detector with crossed wavelength shifting fiber read-out using two ZnS/ 6LiF scintillator sheets

High-intensity pulsed neutron sources have made a great deal of progress in Japan (J-PARC project), the United States (SNS project), and the United Kingdom (ISIS-II project). The specifications required for neutron imaging detectors used at these facilities are a high-position resolution, a high-detection efficiency, a high counting rate, a high n/γ ratio, etc. Especially the detectors which exhibit a high-position resolution and high detection efficiency are required for the crystallography diffractometers. It is also essential for these detectors to be compact and to have the least dead-detection area for a large solid-angle coverage. We have developed a compact high-position-resolution neutron-imaging detector with wavelength shifting (WLS) fibers using two scintillator sheets. The developed detector structure ensures compactness and easy assembly of these types of detectors. It was confirmed that the neutron imaging detector using WLS fibers with a size of 0.5×0.5 mm exhibited a position resolution of less than 0.8 mm. The detection efficiency for thermal neutrons was improved 55% by using the two scintillator sheets from 29% by the single sheet.

New-generation large-area muon scintillation counters with wavelength shifter fiber readout for CDF II

New scintillation counters have been designed and constructed for upgrading the CDF detector at Fermilab Tevatron. A novel light collection technique using wavelength shifting fibers, together with a high-quality polystyrene-based scintillator UPS 923A, has resulted in compact counters with good and stable light collection efficiency over their lengths extending up to 320 cm. The design, construction, and performance of the counters are presented. Properties of the fibers and the scintillator, such as light output, light attenuation, decay time, and long-term stability, are investigated. It is found that the polystyrene-based scintillator, unlike the polyvinyltoluene-based one, has properties more adequate for long-term experiments.

Development of ZnS/6LiF scintillating and MSGC neutron detectors in JAERI

Development of scintillating and gaseous neutron detectors in Japan Atomic Energy Research Institute is briefly described. In this paper, the performances of the developed 2-d neutron detectors, concerning ZnS/6LiF scintillating detectors with wavelength shifting fiber read-out and micro-strip gas chambers with individual read-out, are presented.

Development of a compact scintillator hodoscope with wavelength-shifting fibre read-out

We report on the prototyping of a plastic scintillator hodoscope with wavelength-shifting fibre read-out by a multi-anode photomultiplier as part of the development of a detector for cosmic-ray muons to be carried aboard an aircraft. Light yield and light attenuation measurements on single- and double-clad wavelength-shifting fibres were performed. Low power, low-threshold, discriminators were designed. A prototype 16-channel hodoscope with two planes was built and tested with cosmic rays. After correcting for geometrical factors a global intrinsic efficiency of ε > 98 % was obtained in both planes. The overall performance of the hodoscope proved it to be well suited for the A dler experiment to measure the high-altitude muon flux.

Small scintillating cells as the active elements in a digital hadron calorimeter for the e+e− linear collider detector

The ability to distinguish between hadronic W and Z decays is one of the most challenging requirements for the future linear collider detector. Such sensitivity requires unprecedented jet energy resolution, which may be possible with energy-flow algorithms. A calorimeter that is optimized for energy-flow must have fine lateral and longitudinal segmentation. Small scintillating cells with wavelength shifting fibre readout represent an attractive basis for a digital hadron calorimeter that trades dynamic range for superior granularity, at an affordable price. We present the expected jet resolution for such a device, based on Monte Carlo simulations. Then we describe the initial prototyping studies. In particular, detailed studies are presented on cell performance under different combinations of manufacture and assembly.

Signal processing system based on FPGAs for neutron imaging detectors using scintillators

A signal processing system based on field programmable gate arrays (FPGAs) was developed for a 64 channel×64 channel neutron imaging device using a wavelength shifting fiber read-out based on a photon-counting method. Light signals detected by 64 channel multi-anode photomultipliers are amplified and converted to digital photon signals containing incident-position and time information of neutron by using high-speed amplifiers and discriminators. By using coincidence circuits made in FPGAs, the incident position of neutron is determined based on these digital signals. A neutron imaging detector composed of the signal processing system and a neutron imaging device with a ZnS:Ag/ 6LiF scintillator was evaluated by using neutron beam. It was confirmed that the signal processing based on FPGAs was effective to determine a precise incident position of neutron with high speed and many channel.

Development of a new photomultiplier tube with high sensitivity for a wavelength-shifter fiber readout

We have developed a new photomultiplier tube (PMT) with high sensitivity for a wavelength-shifter fiber readout of plastic scintillators. Improvements of the photoelectron yield were made on a 2-in. PMT (Hamamatsu R329) by adopting (1) a prism-shaped photocathode, (2) an extended-green photocathode material, and (3) an optical mirror surface of the electrodes. As a result, the number of photoelectrons obtained by the new PMT has increased to be 1.8-times that by R329. Other PMT characteristics, such as uniformity of sensitivity, time response and darkcurrent are not so much different from those of R329 for practical applications.

A gamma ray detector with lead-scintillator tiles and WLS fiber readout for the experiment at SPring-8 to study the GDH sum rule

A prototype gamma ray detector for the detection of π 0 in the proposed experiment at SPring-8 to study the Gerasimov–Drell–Hearn (GDH) sum rule (GDH experiment) has been built and tested. The detector is fabricated with lead-scintillator tiles and wave length shifter fiber readout. This detector will be placed inside the bore of the superconducting magnet which supplies the polarized target with a 2.5 T magnetic field. High-detection efficiency (above 85%) for the gamma rays is the most important requirement for this detector to be employed in the proposed experiment. It has been tested with minimum ionizing particles, electrons and gamma rays. The results of the tests in comparison with some Monte Carlo simulations are presented. The evaluated efficiency for gamma rays ranging in energy above 50 MeV is higher than 90%.

Detector for the FSD Fourier-diffractometer Based on ZnS(Ag)/ 6 LiF Scintillation Screen and Wavelength Shifting Fiber Readout

At the IBR-2 pulsed reactor (FLNP, JINR, Dubna), a specialized time-of-flight instrument, the Fourier-Stress-Diffractometer (FSD), is under construction. This instrument is intended for the measurement of internal stresses in bulk samples by using high-resolution neutron diffraction. One of the main components of the diffractometer is a new-type of detector with combined electronic-geometric focusing, uniting a large solid angle and a small geometric contribution to the instrumental resolution. The first two modules of the detector, based on ZnS(Ag)/ 6 LiF scintillation screen with wavelength shifting fiber readout have been developed and tested. In this paper, the design of the detector and associated electronics are described. The method of time focusing surface approximation using the screen flexibility is proposed. Characteristics of tested modules in comparison with a detector of previous generation are presented and advantages of the new detector design for high-resolution diffractometry are discussed.

Light yield measurements in a liquid scintillator detector with wavelength-shifting fibre readout

A technique based on liquid scintillator with wavelength-shifting fibre readout is interesting for large-mass neutrino detectors. In this paper, we present results obtained with a laboratory prototype assembled at CERN. Mixtures made of economical chemical components were compared to commercial liquid scintillators. The light yield was also studied as a function of fibre diameter, fibre position, and surface quality of the container.

Wavelength-shifting fibers for calorimetric measurements in a long base line neutrino oscillation experiment

The NOE Collaboration has proposed a calorimeter to measure the energy of the final states of ν interaction events. The properties of long scintillator bars with wavelength-shifting fiber readout have been studied to develop a calorimeter design option. Various prototypes have been exposed to a cosmic rays stand. The total measured light yield in the middle of a 6 m -long fiber is about 15 photoelectrons. With this photon collection performance, it has been simulated that the calorimeter can achieve 17%/ E and 50%/ E resolutions for electrons and pions, respectively.