Large Area Plastic Scintillation Research Articles

Determining the Position of Gamma-Ray Interaction Using Large Scintillation Detectors and the Least Number of Photomultiplier Tubes

Determining the position of interaction is of great interest for gamma-ray imaging in various nuclear applications. Among all gamma-ray detectors, scintillation detectors are commonly exploited for imaging purposes because they can be prepared in large dimensions and are economically affordable. In this work, the general shape of the measured gamma-ray spectra of two long and large-area plastic scintillation detectors are analyzed by artificial neural networks to determine the position of interaction in one and two dimensions (1D and 2D), respectively. The position of interaction was treated as the position of a 137Cs gamma-ray point source on the long and large-area scintillation detectors. Utilizing this method, only one photomultiplier tube (PMT) was used for 1D positioning of interaction in a 4 × 4 × 35-cm3 long plastic detector, while just two PMTs were applied for 2D positioning of interaction in a 50 × 50 × 5-cm3 large-area plastic detector. The position of interaction in the long detector was determined with a resolution of 1 cm and a mean absolute error of less than 1%, while a resolution of 5 cm with a mean absolute error of 13% was achieved for the large-area detector.

A large area efficient trigger scintillator with SiPM read out

A large area plastic scintillator detector system with SiPM read out has been prepared in order to improve the trigger selectivity for reaction studies induced by an intense proton beam with a beam momentum of several GeV/c. The system consists of six trapezoidal modules, each with three plastic scintillator elements that are each equipped with 12 SiPMs. The detection of a charged particle is based on registering coincident signals in several SiPMs. By requiring a signal on at least two of the SiPMs, the noise rate is negligible and a detection efficiency close to 100% is achieved.

Cosmic ray measurements using the ISMRAN setup in a non-reactor environment

The cosmic rays data collected using a large area plastic scintillator array ISMRAN (Indian Scintillator Matrix for Reactor AntiNeutrino) are presented. The data collected serve as a useful benchmark of cosmogenic background in a non-reactor environment for the future measurements of electron–antineutrinos to be performed using the ISMRAN setup. The zenith angle distribution of the atmospheric muons has been measured and compared with Monte Carlo expectations. The detector setup was further used to measure the lifetime distribution of stopped muons and extract their rates inside the detector matrix. The measured spectra of decaying muons and associated electrons show a good agreement with the MC simulations performed through GEANT4 simulation.

Measurements of gamma ray, cosmic muon and residual neutron background fluxes for rare event search experiments at an underground laboratory

Ambient radiation background contributed by the penetrating cosmic ray particles and the radionuclides present in the rock materials have been measured at an underground laboratory at Jaduguda, Jharkhand, India, located inside a mine at 555 m depth. The laboratory is being set up to explore rare event search processes, such as direct dark matter search, neutrinoless double beta decay, axion search, supernova neutrino detection, etc., that require specific knowledge of the nature and extent of the radiation environment in order to assess the sensitivity reach and also to plan for its reduction for the targeted experiment. The gamma ray background, which is mostly contributed by the primordial radionuclides and their decay chain products, have been measured inside the laboratory and found to be dominated by rock radioactivity for Eγ≲3MeV. Shielding of these residual gamma rays for the experiment was also evaluated. The cosmic muon flux, measured inside the laboratory using large area plastic scintillator telescope, was found to be: (2.257±0.261±0.042)×10−7cm−2s−1, which agrees reasonably well with simulation results. The neutron background flux has been measured for the radiogenic neutrons and found to be: (1.61±0.03)×10−4cm−2s−1 for no threshold cut. Detailed GEANT4 simulation for the radiogenic neutrons and the cosmogenic neutrons have been carried out. Effects of multiple scattering of both the types of neutrons within the surrounding rock and the cavern walls were studied and the results for the radiogenic neutrons are found to be in reasonable agreement with experimental results. Neutron fluxes contributed by those neutrons of cosmogenic origin have been reported as function of the energy threshold.

DM-like anomalies in neutron multiplicity spectra

A new experiment collects data, since November 2019, at a depth of 210 m.w.e. in the Callio Lab in the Pyhasalmi mine in Finland. The setup, called NEMESIS (New Emma MEasurementS Including neutronS), incorporates infrastructure from the EMMA experiment with neutron and large-area plastic scintillator detectors. The experiment’s primary aim is to combine muon tracking with position-sensitive neutron detection to measure precision yields, multiplicities, and lateral distributions of high-multiplicity neutron events induced by cosmic muons in various materials. The data are relevant for background evaluation of the deep-underground searches for Dark Matter (DM), neutrino-less double beta decay, etc. Preliminary analysis revealed anomalies in muon-suppressed neutron multiplicity spectra collected during a 344-day run (live time) with a 565 kg Pb target. The spectra, otherwise well described by an exponential fit, show three peaks at high multiplicities. Although still at a low statistical significance, these small excesses match the outcome of an earlier measurement. The nature of the anomalies remains unclear, but, in principle, they may be a signature of self-annihilation of a WIMP with a mass close to 13 GeV/c2. With that assumption, the expected cross-section would be around 10−42 cm2 for Spin-Dependent or 10−46 cm2 for Spin Independent interactions. We propose verifying this hypothesis with an upgraded NEMESIS experiment, able to collect an order of magnitude more data than this measurement. Based on the statistical uncertainty, analysis of the event rate indicates that cross-section limits for DM mass range of approximately 3-40 GeV/c2 can be investigated with such a setup.

Sb-Doped Metal Halide Nanocrystals: A 0D versus 3D Comparison.

We synthesize colloidal nanocrystals (NCs) of Rb3InCl6, composed of isolated metal halide octahedra (“0D”), and of Cs2NaInCl6 and Cs2KInCl6 double perovskites, where all octahedra share corners and are interconnected (“3D”), with the aim to elucidate and compare their optical features once doped with Sb3+ ions. Our optical and computational analyses evidence that the photoluminescence quantum yield (PLQY) of all these systems is consistently lower than that of the corresponding bulk materials due to the presence of deep surface traps from under-coordinated halide ions. Also, Sb-doped “0D” Rb3InCl6 NCs exhibit a higher PLQY than Sb-doped “3D” Cs2NaInCl6 and Cs2KInCl6 NCs, most likely because excitons responsible for the PL emission migrate to the surface faster in 3D NCs than in 0D NCs. We also observe that all these systems feature a large Stokes shift (varying from system to system), a feature that should be of interest for applications in photon management and scintillation technologies. Scintillation properties are evaluated via radioluminescence experiments, and re-absorption-free waveguiding performance in large-area plastic scintillators is assessed using Monte Carlo ray-tracing simulations.

Determination of Uranium Enrichment Using a Plastic Scintillator

Interest in analyzing the enrichment of uranium waste in drums, which are generated by a nuclear fuel manufacturer, has recently been growing in South Korea. However, high-purity germanium (HPGe) and thallium-doped sodium iodide [NaI(Tl)] that are used to measure uranium enrichment require much time to measure drum size samples because large-area detectors cannot be manufactured due to the limitation of single-crystal growing technologies and the cost. To overcome these limitations, a uranium enrichment analysis device using plastic scintillators is intended to be developed. A screening device using large-area plastic scintillator which is similar to radiation portal monitor is considered for an intermediate- or a low-level uranium waste drum. The capability of plastic scintillators for this application was studied on a small scale by measuring different enrichments of uranium samples using a 2-in plastic scintillator, a 2-in NaI(Tl) scintillator, and an HPGe detector. The results show that the plastic scintillator was able to distinguish between the enrichments of the uranium samples although the efficiency of the plastic scintillator was low. It is expected that this result could be applied to the enrichment analysis of drums containing uranium wastes using large area plastic scintillators in further studies.

Detection of long-lived contaminants in cyclotron-produced radiopharmaceuticals by large area plastic scintillators

In the USA during 2015 over 1,718,500 clinical PET scans were performed in 2380 centers. Patients undergoing these studies will alarm homeland security monitors at borders, ports, and some airports for up to 2 days due to the positron-annihilation photons (0.511 MeV) from the imaging isotope 18F (110 min half-life). In some radiopharmaceuticals, long-lived contaminants generated from the activation and spallation of elements in the HAVAR window of the cyclotron target may also be present in the patient dose. In this work, we have modeled a typical homeland security portal monitor in MCNP, and determined its sensitivity to each of the possible contaminating isotopes found in PET radiopharmaceuticals when distributed in patient phantoms. These data were combined with the time-dependent uptake/retention functions for the contaminating isotopes, to identify the isotopes that can cause alarms for substantial periods of time after the short-lived imaging agent has decayed away.

Study on the Characteristics of a Scintillator for Beta-ray Detection using Epoxy Resin

A thin plate of a plastic scintillator for detecting a beta-ray was developed. The plastic scintillator was made using epoxy resin and organic scintillators such as 2.5-diphenyloxazole (PPO) and 1,4-bis [5-phenyl-2-oxazole] benzene (POPOP). The mixture ratio of epoxy resin and the organic scintillators was determined using their absorbance, transmittance, emission spectra, and transparency. Their optimal weight percentage of PPO and POPOP in the organic scintillators was adjusted to 0.2 wt%:0.01 wt%. The prepared plastic scintillator was used to measure the standard source of Sr-90. The pulse height spectra and total counts of the prepared plastic scintillator were similar to a commercial plastic scintillator. Based on the above results, a large-area plastic scintillator was prepared for rapid investigation of a site contaminated with Sr-90. The prepared large-area plastic scintillator was evaluated for the characteristics in the laboratory. The evaluation results are expected to be usefully utilized in the development of a large-area plastic scintillation detector. The large-area plastic scintillation detector developed on the basis of the evaluation results is expected to be utilized to quickly measure the contamination of Sr-90 in the grounds used as a nuclear power facility.

Ultra-violet light-emitting diode calibration system for timing large area scintillation detectors

Timing large area plastic scintillation detectors are developing for the space gamma-ray telescopes now. For the in-flight calibration of these detectors the use of ultra-violet light-emitting diode, irradiating the 1 m long detector module at the center of its lateral side is suggested. The results of the measurements show the possibility of this calibration system implementation as for amplitude as for timing properties monitoring.

The investigation of timing large area scintillation detectors with SiPM light sensors properties

The timing large area plastic scintillation detectors with silicon photomultipliers as photosensors properties were investigated using a cosmic radiation at the ground level. Different techniques of the amplitude spectra and efficiency measurements were implemented. The measurements results are presented.

A new method for position-sensitive measurement of beta surface contamination

In this paper, we propose a new method for position-sensitive measurement of beta surface contamination. With a position-sensitive detector of enlarged sensitive detection area, accurate information of the contamination distribution can be obtained. The position-sensitive detection is based on a large-area plastic scintillator and the wavelength shifting (WLS) fibers and adopts the “light center of gravity” method. Optical transmission of the detector is simulated with a preliminary detector model, and feasibility of the detector design and measurement method is evaluated using an experiment system. The simulation and experiment results at different beta-ray incident points on the scintillator surface show that there is a polynomial relationship between the average amplitude ratio of the output pulses from the two parallel WLS fibers in the same fiber layer and the relative distance from the incident point to the WLS fiber.

A large area plastic scintillation detector with 4-corner-readout**Supported by National Natural Science Foundation of China (U1332207, 11405242)

A 760 mm × 760 mm × 30 mm plastic scintillation detector viewed by photomultiplier tubes (PMTs) from four corners has been developed, and the detector has been tested with cosmic rays and γ rays. A position-independent effective time Teff has been found, indicating this detector can be used as a TOF detector. The hit position can also be reconstructed by the time from the four corners. A TOF resolution of 236 ps and a position resolution of 48 mm have been achieved, and the detection efficiency has also been investigated.

Geant4-GATE Simulation of a Large Plastic Scintillator for Muon Radiography

Envisaging the possibility of using large-area plastic scintillator slabs as robust detectors for high spatial resolution muon radiography, and prior to prototype development, we study expected basic performance by Monte Carlo simulation. We present preliminary results for a scalable square footprint detector unit of ~ 1 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , defining a representative simulation model volume of 50 cm ×50 cm, with reflective surfaces and a light readout by direct coupling of 4 small PMTs (in a square arrangement) at one face of the scintillator slab. Light detection efficiency is calculated for several light collection configurations, considering different values of surface roughness, reflectivity, optical coupling index and scintillator thickness. Values maximizing photon detection have been identified. The light response function of 2.5-3.5 cm diameter PMTs for the proposed configuration has been determined. A detector intrinsic spatial resolution of the order of 1 cm is estimated for muon interactions at the center region of the detector module, using a simple centroid positioning algorithm (Anger logic).

A new natural gamma radiation measurement system for marine sediment and rock analysis

A new high-efficiency and low-background system for the measurement of natural gamma radioactivity in marine sediment and rock cores retrieved from beneath the seabed was designed, built, and installed on the JOIDES Resolution research vessel. The system includes eight large NaI(Tl) detectors that measure adjacent intervals of the core simultaneously, maximizing counting times and minimizing statistical error for the limited measurement times available during drilling expeditions. Effect to background ratio is maximized with passive lead shielding, including both ordinary and low-activity lead. Large-area plastic scintillator active shielding filters background associated with the high-energy part of cosmic radiation. The new system has at least an order of magnitude higher statistical reliability and significantly enhances data quality compared to other offshore natural gamma radiation (NGR) systems designed to measure geological core samples. Reliable correlations and interpretations of cored intervals are possible at rates of a few counts per second.

The TRACER instrument: A balloon-borne cosmic-ray detector

We describe a large-area detector for measurements of the intensity of cosmic-ray nuclei in balloon-borne exposures. In order to observe individual nuclei at very high energies, the instrument employs transition radiation detectors (TRD) whose energy response extends well beyond 104 GeV amu−1. The TR measurement is performed with arrays of single-wire proportional tubes interleaved with plastic-fiber radiators. An additional energy determination comes from the specific ionization in gas and its relativistic rise which is also measured with proportional tubes. The tubes also determine the trajectory of each cosmic-ray nucleus with mm-resolution. In total, nearly 1600 tubes are used. The instrument is triggered by large-area plastic scintillators. The scintillators, together with acrylic Cherenkov counters, also determine the nuclear charge Z of each cosmic-ray particle, measure the energy in the GeV amu−1 region, and discriminate against low-energy background. We describe the details of this detector system, and discuss its performance in three high-altitude balloon flights, including two long-duration flights in 2003 and 2006 at Antarctic and Arctic latitudes, respectively. Scientific results from these flights are summarized, and possible future developments are reviewed.

Monte Carlo investigation and optimization of coincidence prompt gamma-ray neutron activation analysis

Normal Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) suffers from a large inherent noise or background. The coincidence PGNAA approach is being investigated for eliminating almost all of the interfering backgrounds and thereby significantly improving the signal-to-noise ratio (SNR). This can be done since almost all of the prompt gamma rays from elements of interest are emitted in coincidence except hydrogen. However, it has been found previously that while the use of two normal NaI detectors greatly reduces the background, the signal is also greatly reduced so that very little improvement in standard deviation is obtained. With the help of MCNP5, the general-purpose Monte Carlo N-Particle code, and CEARCPG, the specific purpose Monte Carlo code for Coincidence PGNAA, further optimization of the proposed coincidence system is being accomplished. The idea pursued here is the use of a large area plastic scintillation detector as the trigger for coincidence events together with a normal large NaI detector. In this approach the detection solid angle is increased greatly, which directly increases the probability of coincidence detection. The 2D-coincidence spectrum obtained can then be projected to the axis representing the NaI detector to overcome the drawback of low energy resolution and photopeak intensity of the plastic scintillation detector and utilize the overall higher coincidence counting rate. To reach the best coincidence detection, the placement of detectors, sample, and the moderator of the neutron source have been optimized through Monte Carlo simulation.

A large area plastic scintillator detector array for fast neutron measurements

A large area plastic scintillator detector array ( ∼ 1 × 1 m 2 ) has been set up for fast neutron spectroscopy at the BARC-TIFR Pelletron laboratory, Mumbai. The energy, time and position response has been measured for electrons using radioactive sources and for monoenergetic neutrons using the 7Li ( p , n 1 ) 7 Be * ( 0.429 MeV ) reaction at proton energies between 6.3 and 19 MeV. A Monte Carlo simulation of the energy dependent efficiency of the array for neutron detection is in agreement with the 7Li ( p , n 1 ) measurements. The array has been used to measure the neutron spectrum, in the energy range of 4–12 MeV, in the reaction C 12 + Nb 93 at E ( C 12 ) = 40 MeV . This is in reasonable agreement with a statistical model calculation.

Development of MRG10 Mobile Roadway Gamma Monitor

The MRG10 mobile roadway gamma monitor is described in this paper. This system is developed to meet requirements to survey roadways for gamma contamination in nuclear power plants and other nuclear facilities. The system consists of a four wheel electric utility vehicle, two detector modules and a MCU based controller. The detector module consists of a lead shielded large area plastic scintillator(1000×500×50 mm), a PMT and amplifier unit, a MCU based counting unit, and a semiconductor cooler. The detector module and controller unit are connected with RS-485 bus. When a survey starts, the controller unit takes control of the vehicle speed, displays the measurement data, and will switch on the semiconductor cooler when the temperature of detector module is higher than a set point.

CsI(Tl)/plastic phoswich detector enhanced in low-energy gamma-ray detection

A phoswich detector composed of a thin plate CsI(Tl) scintillator and a plastic scintillator (BC-400) has been designed and evaluated in order to improve the sensitivity in the low-energy region of a large-area plastic scintillation detector. This newly designed phoswich detector can be applied to both gross gamma measurement and energy spectrometry for low-energy gamma-ray emitters. Judging by estimations of minimum detectable activity, the lower measurable energy of a large-area plastic scintillation detector can be expanded down to a few tens of keV by adding a thin plate CsI(Tl) scintillator.