Thick Plastic Scintillator Research Articles

First measurements with a new β-electron detector for spectral shape studies

The shape of the electron spectrum emitted in β decay carries a wealth of information about nuclear structure and fundamental physics. In spite of that, few dedicated measurements have been made of β-spectrum shapes. In this work we present a newly developed detector for β electrons based on a telescope concept. A thick plastic scintillator is employed in coincidence with a thin silicon detector. The first measurements employing this detector have been carried out with mono-energetic electrons from the high-energy resolution electron-beam spectrometer at Bordeaux. Here we report on the good reproduction of the experimental spectra of mono-energetic electrons using Monte Carlo simulations. This is a crucial step for future experiments, where a detailed Monte Carlo characterization of the detector is needed to determine the shape of the β-electron spectra by deconvolution of the measured spectra with the response function of the detector. A chamber to contain two telescope assemblies has been designed for future β-decay experiments at the Ion Guide Isotope Separator On-Line facility in Jyväskylä, aimed at improving our understanding of reactor antineutrino spectra.

Measurement of the detection efficiency of a 100 µm thin plastic scintillator for muons with p = 28 MeV/c

In the muEDM experiment, a gate detector is used to trigger the storage mechanism when a muon enters the experimental apparatus. This detector should operate at full efficiency and low thermal noise contamination. Furthermore, it should have a very low material budget to minimize the deflection of the muon trajectory by multiple coulomb scattering. A first prototype of this detector is a 100 µm thick plastic scintillator, connected to eight silicon photomultipliers reading out the scintillation light. In a dedicated beamtime at the πE1 beamline at the Paul Scherrer Institute, we measured the detection efficiency of this scintillator with 28 MeV/c muons.

A new technique to enhance the position resolution of large area plastic scinitillators to reconstruct the cosmic muon tracks

In this paper, we present a study to use thick plastic scintillators to reconstruct the cosmic muon tracks, that can be used for the applications like Muon Tomography. At Bhabha Atomic Research Centre (BARC), India, a plastic scintillator array — `ISMRAN (Indian Scintillator Matrix for Reactor Anti-Neutrinos),' with a total weight of 1.0 ton has been configured for neutrino physics study. Using the ISMRAN scintillators matrix, we present a technique of the position calibration of thick plastic scintillators using cosmic muons as a probe. The position resolution obtained from the cosmic muons based calibration method is compared with the one obtained from the traditional calibration method using the radioactive source. Finally, the accuracy of reconstructed cosmic muon tracks from the two position calibration techniques is compared using the χ2/ndf distribution of the fitted cosmic muon tracks.

A method to measure the integral vertical intensity and angular distribution of atmospheric muons with a stationary plastic scintillator bar detector

We present a method to measure the integral vertical intensity and angular distribution of atmospheric muons using a stationary thick plastic scintillator bar detector with PMTs at both of its ends over exposures of a few hours in a laboratory setting. The total flux is obtained from the event rate and the angular distribution is inferred from the distribution of the recorded pulse charges, which are correlated with the track length inside the plastic scintillator. A muon generator algorithm was developed and used together with a simple simulation including the effects of the detector resolution, nonlinear saturation of the PMTs, and laboratory building coverage. As a proof of principle we made a measurement assuming a standard cosnθ omnienergetic angular distribution with azimuthal isotropy and different models for the energy spectrum of the source. Using measurements at 5 different azimuthal orientations, we measure an average exponent n=(1.90±0.06(stat)±0.10(syst)), and an average vertical intensity of I0=(101.2±1.8(stat)±5.5(syst))m−2s−1sr−1 at the location with geographic coordinates 19.33°N 99.19°W, altitude 2268 m above sea level, and geomagnetic cut-off of 8.2 GV.

X-ray detection properties of Bi-loaded plastic scintillators synthesized via solvent evaporation

Bi-loaded plastic scintillators were successfully synthesized using the solvent evaporation method and were used as detectors for synchrotron X-ray radiation. The photoluminescence emission spectra and X-ray-excited radioluminescence spectra of all prepared plastic scintillators presented broad emission bands in the range of 350–500 nm, which derived from the fluorescence of the organic phosphor, 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole. The detection efficiency of 1 mm thick plastic scintillators for high-energy X-ray photons was increased by the addition of Bi compounds (up to 2.3 wt%) and reached 67% of that of EJ-256, the commercially available Pb 5 wt% loaded plastic scintillator. Subnanosecond time resolution was successfully achieved for all scintillators.

Design and Optimisation of a Three Layers Thermal Neutron, Fast Neutron and Gamma-Ray Imaging System

The design and configuration of a multi-layered imaging system with the ability to detect thermal neutrons, fast neutrons and gamma rays has been developed and its efficacy demonstrated. The work presented here numerically determines the systems efficiency and spatial resolution, using 252Cf and 137Cs as a case study. The novelty of this detection system lies in the use of small form factor detectors in a three-layer design, which utilises neutron elastic scattering and Compton scattering simultaneously. The current configuration consists of 10 mm thick natural lithium glass (GS10) scintillator integrated with a 20 mm thick plastic scintillator (EJ-204) in the first layer, a 15 mm thick lithium glass (GS10) scintillator in the second and a 30 mm thick CsI(Tl) scintillator forming the final layer. Each of these layers is backed with an 8 x 8 silicon photomultiplier diode (SiPM) array. The overall size of the imaging system is 27 mm x 27 mm x 135 mm. MCNPv6.1 and Geant4-10.04 were alternatively used to optimise the overall configuration and to investigate detection modalities. Results show promising performance with high precision source localisation and characterization abilities. Measurements were virtually obtained of two gamma-ray sources within steel enclosures at angles of 15°, 30° and 50° separation in order to test spatial resolution ability of the system. With the current active size of the system and the 8x8 SiPM configuration, the results estimate the spatial resolution to be close to 30°. The ability of the system to characterise and identify sources based on the type and energy of the radiation emitted, has been investigated and results show that for all radiation types the system can identify the source energy within the energy range of typical reported sources in literature.

Determination of Environmental Radiation in the Beach Sand of Tatvan, Ahlat and Adilcevaz

The determination of radiation level is important in living areas for human health. The aim of this study is to determine environmental radiation in the beach sands of Tatvan, Ahlat and Adilcevaz. Environmental gamma radiation and alpha-beta concentrations determined for 15 different points. It has used portable gamma survey meter which is NaI(TI) scintillation detector. Also, it has used portable alpha-beta survey meter which consist of ZnS(Ag) scintillator adhered to 0.25 cm (0.010 in) thick plastic scintillator. Obtained results were compared with literature.

Estimation of the three-dimensional (3D) dose distribution of electron beams from medical linear accelerator (LINAC) using plastic scintillator plate

Measurements of three-dimensional (3D) dose distribution of electron-beams in water are important for high-energy electron beams from medical linear accelerators (LINAC). Although ionization chambers are commonly used for this purpose, measurements take a long time for precise 3D dose distribution. To solve the problem, we tried the measurements of the 3D dose distributions using a scintillator plate combined with a mirror. After we placed a 1 mm thick plastic scintillator plate at the upper inside of a black box, a water phantom was set above the plastic scintillator plate outside the black box, and electron beam was irradiated to the water phantom from the upper side. The attenuated electron-beam by the water in the phantom was detected by the plastic scintillator plate and the scintillation image was formed in the plate. The image was reflected by a surface mirror set below the plastic scintillator plate and detected by a cooled charge coupled device (CCD) camera from the side. We changed the depths of the water in the phantom, obtained the scintillation images, and calculated a 3D scintillation image using the measured images. Measurements were made for 9 MeV and 12 MeV electron-beams using the imaging system. From the images, we could successfully form 3D scintillation images. The depth profiles measured from the 3D images showed almost identical distribution with those calculated by the planning system within the difference of 5%. The lateral profiles also showed almost identical within the difference of the widths less than 2.5 mm. We conclude that the proposed method is promising for 3D dose distribution measurements of electron-beams.

Multisector scintillation detector with fiber-optic light collection

A new type of scintillation detector for the use in high energy physics is described. The octagonal detector consists of eight triangular scintillator sectors with total area of 1 m2. Each sector represents two plates of 2 cm thick plastic scintillator. Seven 1 mm thick WLS fibers are laid evenly between the plates. The space between the fibers is filled with silicone compound to provide better light collection. Fiber ends from all eight sectors are gathered in the central part of the detector into a bunch and docked to the cathode of a FEU-115m photomultiplier. The read-out of the counter signals is carried out from 7th and 12th dynodes, providing a wide dynamic range up to about 10000 particles. The front-end electronics of the detector is based on the flash-ADC with a sampling frequency of 200 MHz. The features of detecting and recording systems of the multisector scintillation detector (MSD) and the results of its testing are discussed.

Development of shashlik electromagnetic calorimeter prototype for SoLID

A shashlik electromagnetic calorimeter will be produced in Hall A of Jefferson Laboratory for Solenoidal large Intensity Device (SoLID) to measure the energy deposition of electrons and hadrons, and to provide particle identification after the energy of the accelerator was upgraded to 12 GeV. Tsinghua University is the member of Hall A collaboration in charge of development and production of the large shashlik electromagnetic calorimeter of SoLID. One module of that calorimeter is composed by 194 layers. Each layer consists of a 1.5 mm thick plastic scintillator put on top of a 0.5 mm thick lead plate. Scintillation light is read out by wave-length shifter fibers penetrating through the calorimeter modules longitudinally along the direction of flight of the impact particle. This paper describes the design and construction of that module, as well as a few optimization studies meant to improve its performance. A detailed Geant4 simulation also shows that an energy resolution of 5%/√ E (GeV) and a good containment for electromagnetic showers can be achieved, as well as some basic electron identification. A prototype of that module will be tested soon with an electron beam at JLab.

Upgrade of In-Beam Charged Particle Detector for the KOTO Experiment

The KOTO experiment aims at measuring the branching ratio of the decay. Since the decay is highly suppressed in the Standard Model, it is sensitive to new physics beyond the standard model. In the KOTO experiment, two photons from the π0 in the final state are detected by an electromagnetic calorimeter, and the absence of extra particles except for the escaping neutrinos is ensured by the surrounding veto counters. As one of the veto counters, an in-beam charged particle detector, composed of 3-mm thick plastic scintillators, covered the beam hole of the calorimeter. It was operating in a high-rate environment with a single counting rate of 10 MHz, which caused 10% loss to the signal. To reduce the hits by neutral particles, the detector has been upgraded to a thin-gap wire chamber. Keeping a high detection efficiency over 99.6% for penetrating charged particles, a 65% reduction of the single counting rate was achieved, corresponding to 40% recovery of acceptance for .

Fast neutron radiography and tomography at a 10 MW research reactor beamline

Fast neutron imaging was performed using a beamline of the 10MW research reactor of the Budapest Neutron Centre, Hungary. A simple, low-cost 2D area detector has been used featuring a 8mm thick BC400 plastic scintillator converter screen and a CCD camera. A spatial resolution of around 1.3mm has been achieved. Typically 10min long exposures were needed to obtain reasonable quality radiographic images. For tomographic imaging typically several hours of acquisition were needed to obtain reasonable quality on non-symmetric and larger (e.g. 10×10×10cm3) objects. Due to the presence of a significant gamma background at the experimental position, massive (30cm thick) lead shielding and filtering was applied to the beam. The gamma contribution was mostly baseline independent of the object imaged and therefore could be subtracted, whereas the direct gamma contribution from the beam to the imaging detector signal is estimated to be less than 1%.

Determination of the energy dependence of the BC-408 plastic scintillation detector in medium energy x-ray beams

The energy dependence of the response of BC-408 plastic scintillator (PS), an approximately water-equivalent material, has been investigated by employing standardized x-ray beams. IEC RQA and ISO N series x-ray beam qualities, in the range of 40–100 kVp, were calibrated using a PTW-type ionization chamber. The energy response of a thick BC-408 PS detector was measured using the multichannel pulse height analysis method.The response of BC-408 PS increased gradually with increasing energy in the energy range of 40–80 kVp and then showed a flat behavior at about 80 to 120 kVp. This might be due to the self-attenuation of scintillation light by the scintillator itself and may also be partly due to the ionization quenching, leading to a reduction in the intensity of the light output from the scintillator. The results indicated that the sensitivity drop in BC-408 PS material at lower photon energies may be overcome by adding some high-Z elements to its polyvinyltoluene (PVT) base. The material modification may compensate for the drop in the response at lower photon energies. Thus plastic scintillation dosimetry is potentially suitable for applications in diagnostic radiology.

Predicted CALET measurements of electron and positron spectra from 3 to 20 GeV using the geomagnetic field

The CALorimetric Electron Telescope (CALET) is an imaging calorimeter under construction for launch to the ISS in 2014 for a planned 5year mission. CALET consists of a charge detection module (CHD) with two segmented planes of 1cm thick plastic scintillator, an imaging calorimeter (IMC) with a total of 3 radiation lengths (X∘) of tungsten plates read out with 8 planes of interleaved scintillating fibers, and a total absorption calorimeter (TASC) with 27 X∘ of lead tungstate (PWO) logs. The primary objectives of the experiment are to measure the electron e-+e+ energy spectra from 1GeV to 20TeV, to detect gamma-rays above 10GeV, and to measure the energy spectra of nuclei from protons through iron up to 1000TeV. In this paper we describe how the geomagnetic field at the 51.6° inclination orbit of the ISS can be used to allow CALET to measure the distinct electron and positron fluxes. The positron fraction has been seen to rise above ∼10GeV by previous experiments (HEAT, AMS-01), and more recently to continue to increase to higher energies (∼80GeV for PAMELA, ∼200GeV for Fermi and ∼350GeV with the best statistics for AMS-02). Utilizing the geomagnetic cutoff, CALET will be able to distinguish electrons and positrons in the ∼3–20GeV energy range where the positron fraction turns upward to complement existing high statistics measurements.

Predicted CALET measurements of ultra-heavy cosmic ray relative abundances

The CALorimetric Electron Telescope (CALET) is an imaging calorimeter under construction for launch to the ISS in 2014 for a planned 5year mission. CALET consists of a charge detection module (CHD) with two segmented planes of 1cm thick plastic scintillator, an imaging calorimeter (IMC) with a total of 3 radiation lengths (X∘) of tungsten plates read out with 8 planes of interleaved scintillating fibers, and a total absorption calorimeter (TASC) with 27 X∘ of lead tungstate (PWO) logs. The primary objectives of the instrument are to measure electron energy spectra from 1GeV to 20TeV, to detect gamma-rays above 10GeV, and to measure the energy spectra of nuclei from protons through iron up to 1,000TeV. In this paper we describe how the geomagnetic field at the 51.6° inclination orbit of the ISS can be used to allow CALET to measure the rare ultra-heavy (UH) cosmic ray (CR) abundances, which provide important clues for the CR source and acceleration mechanism. The CHD scintillator response is relatively insensitive to energy above minimum ionization, and the angle-dependent rigidity as a function of geomagnetic latitude can be exploited to discriminate particles above this energy threshold. Such events require corrections for trajectory in instrument that can be made with only the top 4 layers of the IMC, which allows for considerably greater geometric acceptance than for events that require passage through the TASC for energy determination. Using this approach CALET will be able to measure UH CR relative abundances over its expected mission with superior statistics to previous space instruments.

Electrical characteristics and radiation detection performance of large-area photodiodes

Photodiodes with the size of 2.3 × 2.3 cm2 are fabricated on n-type silicon wafers with high resistivity (>5 kΩ·cm) for physics applications. The photodiodes are fully depleted to collect signals produced by incoming particles. We measure the leakage currents and the capacitances of the photodiodes as functions of the reverse bias voltage. The photodiodes with leakage currents < 70 nA/cm2 are used to measure the signal-to-noise ratio (SNR) by using a 45 MeV proton beam from the MC-50 cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS) and a 90Sr radioactive source. The SNRs are measured for the photodiode only and for photodiode coupled with a 5 mm thick plastic scintillator. The proton beam energy is controlled by using a degrader, and the pulse heights are measured for different energies of the proton beam. The radiation damage effect is also measured in an environment of 1.18 × 1010 protons/cm2. In this paper, we present not only the SNR measurements using the proton beam and the radioactive source but also the result of the radiation damage test.

Stopped cosmic-ray muons in plastic scintillators on the surface and at the depth of 25 m.w.e

Cosmic ray muons stopped in 5 cm thick plastic scintillators at surface and at depth of 25 m.w.e are studied. Apart from the stopped muon rate we measured the spectrum of muon decay electrons and the degree of polarization of stopped muons. Preliminary results for the Michel parameter yield values lower than the currently accepted one, while the asymmetry between the numbers of decay positrons registered in the upper and lower hemispheres appear higher than expected on the basis of numerous earlier studies.

New low threshold detectors for measuring electron and gamma ray fluxes from thunderclouds

Strong electric fields inside thunderclouds give rise to enhanced fluxes of high-energy electrons and, consequently, gamma rays and neutrons. During thunderstorms at mountain Aragats, hundreds of Thunderstorm Ground Enhancements (TGEs) comprising millions of energetic electrons and gamma rays, as well as neutrons, were detected at Aragats Space Environmental Center (ASEC) on 3200 m altitude. The energy spectra of the electrons have an exponential shape and extend in energy range 2- 30 MeV. Recovered energy spectra of the gamma rays is also exponential in energy range 2-10 MeV, then turns to power law and is extending up to 100 MeV. It is of upmost importance to research energy spectra of TGE electrons and gamma rays from the lowest possible energies to clarify the shape of energy spectra and huge multiplication of the avalanche particles. The particle detectors operated at ASEC was designed for the registration of solar modulation effects and the lowering energy threshold was not of first importance. Thus, particle detectors have energy threshold of 7-10 MeV. The new generation of ASEC detectors comprises from 1 and 3 cm thick molded plastic scintillators arranged in stacks (3cm and 1cm STAND detectors) and in cubical structures surrounded thick scintillators and NaI crystals for purification of detected neutral flux (Cube 1 cm and Cube 3 cm detectors). In presented paper we describe new detectors and analyze their operational characteristics, as well as provide examples of TGE detection with new techniques.

PhytoBeta imager: a positron imager for plant biology

Several positron emitting radioisotopes such as 11C and 13N can be used in plant biology research. The 11CO2 tracer is used to facilitate plant biology research toward optimization of plant productivity, biofuel development and carbon sequestration in biomass. Positron emission tomography (PET) imaging has been used to study carbon transport in live plants using 11CO2. Because plants typically have very thin leaves, little medium is present for the emitted positrons to undergo an annihilation event. The emitted positrons from 11C (maximum energy 960 keV) could require up to approximately 4 mm of water equivalent material for positron annihilation. Thus many of the positrons do not annihilate inside the leaf, resulting in limited sensitivity for PET imaging. To address this problem we have developed a compact beta-positive, beta-minus particle imager (PhytoBeta imager) for 11CO2 leaf imaging. The detector is based on a Hamamatsu H8500 position sensitive photomultiplier tube optically coupled via optical grease to a 0.5 mm thick Eljen EJ-212 plastic scintillator. The detector is equipped with a flexible arm to allow its placement and orientation over or under the leaf to be studied while maintaining the leaf's original orientation. To test the utility of the system the detector was used to measure carbon translocation in a leaf of the spicebush (Lindera benzoin) under two transient light conditions.

Response Functions of Phoswich-Type Neutron Detector for High-Energy Cosmic Ray Neutron Measurement

A phoswich-type neutron detector was developed in order to measure high-energy cosmic ray neutron spectra in aircraft. The neutron detector consists of an EJ309 organic liquid scintillator that is 121.7mm in diameter and 121.7mm in length and is covered with a 15mm thick EJ299-13 outer plastic scintillator. The neutron response functions of the detector are required for the unfolding method to obtain the energy spectrum. The neutron response functions were created based on MCNPX simulations using an anticoincidence mode with the experimental light-output correlations with particle energies, uniformity of light collection and energy resolutions. The light-output correlation with particle energy, the uniformity of light collection and the energy resolutions were evaluated based on experiments. Measurements of neutron response functions were performed using four quasi-monoenergetic neutron beams from 40 to 80 MeV p-Li reactions to verify the calculated results. The calculated response functions show good agreement with the measurements. The angular response of the phoswich detector was confirmed to be isotropic from the calculation. The photon response functions of the detector were also calculated and agreed well with the measurements for 6.129MeV photons. Neutron and photon response matrices were created up to 300 and 50 MeV, respectively, over a wide energy range for experimental flights.