Scintillator Array Research Articles

A new charged particle detector for the KOTO experiment at J-PARC

We report the performance of a new scintillator array Downstream Charged Veto (DCV) for the J-PARC KOTO experiment to suppress the K L → π + π − π 0 decay background. Since the background originates from undetected charged pions passing through the beam hole of the electromagnetic calorimeter, the DCV detector was installed in vacuum downstream of the calorimeter. The DCV is composed of two plastic scintillator pipes read out by Multi Pixel Photon Counters through wavelength shifting fibers. The light yield was found to be 60 photoelectrons/0.8 MeV in a test bench when cosmic-rays pass through the center of the DCV. Energy calibration was performed using cosmic-rays after installation.

Machine learning technique to improve anti-neutrino detection efficiency for the ISMRAN experiment

The Indian Scintillator Matrix for Reactor Anti-Neutrino detection—ISMRAN experiment aims to detect electron anti-neutrinos (ν̄e) emitted from a reactor via inverse beta decay reaction (IBD). The setup, consisting of 1 ton segmented Gadolinium foil wrapped plastic scintillator array, is planned for remote reactor monitoring and sterile neutrino search. The detection of prompt positron and delayed neutron from IBD will provide the signature of ν̄e event in ISMRAN. The number of segments with energy deposit (Nbars) and sum total of these deposited energies are used as discriminants for identifying prompt positron event and delayed neutron capture event. However, a simple cut based selection of above variables leads to a low ν̄e signal detection efficiency due to overlapping region of Nbars and sum energy for the prompt and delayed events. Multivariate analysis (MVA) tools, employing variables suitably tuned for discrimination, can be useful in such scenarios. In this work we report the results from an application of artificial neural network—the multilayer perceptron (MLP), particularly the Bayesian extension—MLPBNN, to the simulated signal and background events in ISMRAN. The results from application of MLP to classify prompt positron events from delayed neutron capture events on Hydrogen, Gadolinium nuclei and also from the typical reactor γ-ray and fast neutron backgrounds is reported. An enhanced efficiency of ∼ 91% with a background rejection of ∼ 73% for prompt selection and an efficiency of ∼ 89% with a background rejection of ∼ 71% for the delayed capture event, is achieved using the MLPBNN classifier for the ISMRAN experiment.

Calibration of large neutron detection arrays using cosmic rays

Cosmic muons are used to calibrate the position, light output and the relative timing offset of the Large Area Neutron Array (LANA). Each 2×2m2 LANA wall consists of twenty-five horizontal neutron detection bars. Each bar is 2 m long with a cross-section of 6.35×7.62cm2 Pyrex container filled with NE-213 organic scintillation liquid. The average position and time resolution of a bar is found to be about 8 cm and 500 ps FWHM, respectively. Our method provides an accurate, fast and convenient calibration of LANA that can be applied to general scintillation arrays without the use of radioactive sources or beams.

High-Resolution Depth-Encoding PET Detector Module with Prismatoid Light-Guide Array.

Depth-encoding detectors with single-ended readout provide a practical, cost-effective approach for constructing high-resolution and high-sensitivity PET scanners. However, the current iteration of such detectors uses a uniform glass light-guide to achieve depth encoding, resulting in nonuniform performance throughout the detector array due to suboptimal intercrystal light sharing. We introduce Prism-PET, a single-ended-readout PET detector module with a segmented light-guide composed of an array of prismatoids that introduce enhanced, deterministic light sharing. Methods: High-resolution PET detector modules were fabricated with single-ended readout of polished multicrystal lutetium yttrium orthosilicate scintillator arrays directly coupled 4-to-1 and 9-to-1 to arrays of 3 × 3 mm silicon photomultiplier pixels. Each scintillator array was coupled at the nonreadout side to a light-guide (one 4-to-1 module with a uniform glass light-guide, one 4-to-1 Prism-PET module, and one 9-to-1 Prism-PET module) to introduce intercrystal light sharing, which closely mimics the behavior of dual-ended readout, with the additional benefit of improved crystal identification. Flood histogram data were acquired using a 3-MBq 22Na source to characterize crystal identification and energy resolution. Lead collimation was used to acquire data at specific depths to determine depth-of-interaction (DOI) resolution. Results: The flood histogram measurements showed excellent and uniform crystal separation throughout the Prism-PET modules, whereas the uniform glass light-guide module had performance degradation at the edges and corners. A DOI resolution of 5.0 mm full width at half maximum (FWHM) and an energy resolution of 13% FWHM were obtained in the uniform glass light-guide module. By comparison, the 4-to-1 coupled Prism-PET module achieved a DOI resolution of 2.5 mm FWHM and an energy resolution of 9% FWHM. Conclusion: PET scanners based on our Prism-PET modules with segmented prismatoid light-guide arrays can achieve high and uniform spatial resolution (9-to-1 coupling with ∼1-mm crystals), high sensitivity (20-mm-thick detectors and intercrystal Compton scatter recovery), good energy and timing resolutions (using polished crystals and after applying DOI correction), and compact size (depth encoding eliminates parallax error and permits smaller ring-diameter).

Testing ab initio nuclear structure in neutron-rich nuclei: Lifetime measurements of second 2+ state in C16 and O20

To test the predictive power of ab initio nuclear structure theory, the lifetime of the second 2+ state in neutron-rich 20O, tau(2+_2 ) = 150(+80-30) fs, and an estimate for the lifetime of the second 2+ state in 16C have been obtained, for the first time. The results were achieved via a novel Monte Carlo technique that allowed us to measure nuclear state lifetimes in the tens-to-hundreds femtoseconds range, by analyzing the Doppler-shifted gamma-transition line shapes of products of low-energy transfer and deep-inelastic processes in the reaction 18O (7.0 MeV/u) + 181Ta. The requested sensitivity could only be reached owing to the excellent performances of the AGATA gamma-tracking array, coupled to the PARIS scintillator array and to the VAMOS++ magnetic spectrometer. The experimental lifetimes agree with predictions of ab initio calculations using two- and three-nucleon interactions, obtained with the valence-space in-medium similarity renormalization group for 20O, and with the no-core shell model for 16C. The present measurement shows the power of electromagnetic observables, determined with high-precision gamma spectroscopy, to assess the quality of first-principles nuclear structure calculations, complementing common benchmarks based on nuclear energies. The proposed experimental approach will be essential for short lifetimes measurements in unexplored regions of the nuclear chart, including r-process nuclei, when intense ISOL-type beams become available.

Monte Carlo Calculations of the Detection Efficiency of Composite Scintillator Arrays for Fast and Moderated Neutrons, and for Gamma-Ray Spectroscopy

Fissionable materials can be distinguished from normal materials by their emission of fast neutrons and neutrons moderated by surrounding materials. Radioisotopes can often be identified by their gamma-ray spectra. In this work, we use the nuclear physics Monte Carlo package MCNP6.2 to compare the detection efficiencies of different detector designs for the triple-mode detection of fast and moderated neutrons, and gamma-ray spectroscopy. For each design, we tabulate the detection efficiencies for neutrons from 0.1 eV to 5 MeV and for the full absorption of gamma rays from 0.1 to 5 MeV. All designs use 100 scintillators 1 cm $\times $ 1 cm $\times $ 5 cm. Of these, 36 are Cs2 LiLaBr6:Ce (90% 6Li) (CLLB) and 64 are polyvinyl toluene (PVT). The first design uses separate arrays of $6\times 6$ CLLB and $8\times 8$ PVT scintillators. Three other designs are $10\times 10$ composite arrays using all 100 scintillators combined in different ways. PVT is a fast scintillator that can be used to detect fast neutrons by time-separated multiple proton recoils and discriminate against gammas. PVT in the three composite designs serves to moderate neutrons of all energies for capture by the 6Li in the CLLB. Gamma rays interact in the PVT and CLLB by Compton scattering and pair production; full energy absorption requires photoelectric absorption in the CLLB. The energy deposited by each gamma ray can be determined from a weighted sum of the CLLB and PVT signals from separate photodetectors. We find that for a fixed number of neutrons/cm2, one of the composite arrays has much higher 6Li detection efficiencies than the design that uses separate CLLB and PVT arrays, and has similar detection efficiencies for fast neutrons and gammas. We also find that in all cases, the average energy of the neutrons at capture by 6Li is well above the 25-meV thermal energy.

Design, evaluation and initial imaging results of a PET insert based on strip-line readout for simultaneous PET/MRI

We present the development of a PET insert system for potential simultaneous PET/MR imaging using a 9.4 T small animal MRI scanner to test our system. The detectors of the system adopt a strip-line based multiplexing readout method for SiPM signals. In this readout, multiple SiPM outputs in a row share a common strip-line. The position information about a hit SiPM is encoded in the propagation time difference of the signals arriving at the two ends of the strip-line. The use of strip-lines allows us to place the data acquisition electronics remotely from the detector module to greatly simplify the design of the detector module and minimize the mutual electromagnetic interference. The prototype is comprised of 14 detector modules, each of which consists of an 8x4 LYSO scintillator array (each LYSO crystal is 3x3x10 mm3) coupled to two units of Hamamatsu MPPC arrays (4x4, 3.2 mm pitch) that are mounted on a strip-line board. On the strip-line board, outputs of the 32 SiPMs are routed to 2 strip-lines so that 16 SiPM signals share a strip-line. The detector modules are installed inside a plastic cylindrical supporting structure with an inner and outer diameter of 60 mm and 115 mm, respectively, to fit inside a Bruker BioSpec 9.4 T MR scanner. The axial field of view of the prototype is 25.4 mm. The strip-lines were extended by using 5-meter cables to a sampling data acquisition (DAQ) board placed outside the magnet. The detectors were not shielded in the interest of investigating how they may affect and be affected by the MRI. Experimental tests were conducted to evaluate detection performance, and phantom and animal imaging were carried out to assess the spatial resolution and the MR compatibility of the PET insert. Initial results are encouraging and demonstrate that the prototype insert PET can potentially be used for PET/MR imaging if appropriate shielding will be implemented for minimizing the mutual interference between the PET and MRI systems.

Performance evaluation of HiPET, a high sensitivity and high resolution preclinical PET tomograph

HiPET is a recently developed prototype preclinical PET scanner dedicated to high sensitivity and high resolution molecular imaging. The HiPET system employs a phoswich depth of interaction (DOI) detector design, which also allows identification of the large majority of the cross layer crystal scatter (CLCS) events. This work evaluates its performance characteristics following the National Electrical Manufacturers Association (NEMA) NU4-2008 protocol.The HiPET consists of twenty flat panel type detectors arranged in two rings. The inner diameter is 160 mm and the axial field of view (FOV) is 104 mm. Each detector is comprised of two layers of phoswich scintillator crystal arrays, a tapered, pixelated glass lightguide and a multi anode photomultiplier tube (MAPMT). The front (gamma ray entrance) layer is a 48 × 48 pixelated cerium doped lutetium yttrium orthosilicate (LYSO) scintillator array with individual crystals measuring 1.01 × 1.01 × 6.1 mm. The back (towards the PMT) layer is a 32 × 32 pixelated bismuth germanate (BGO) scintillator array with individual crystals measuring 1.55 × 1.55 × 8.9 mm.For energy windows of 250–650 keV and 350–650 keV, the peak absolute sensitivity at the center of the FOV was 13.5% and 10.4% including CLCS events, and 11.8% and 8.9% excluding CLCS events, respectively. The average detector energy resolution derived by averaging the individual crystal spectra was 11.7% ± 1.4% for LYSO and 17.0% ± 1.4% for BGO. The 3D ordered-subsets expectation maximization (OSEM) reconstructed image of a point source in air, ranged from 0.73 mm to 1.19 mm, with an average value of 0.93 ± 0.09 mm at all measured locations. The peak noise equivalent count rate (NECR) and scatter fraction were 179 kcps at 12.4 MBq and 6.9% for the mouse-sized phantom, and 63 kcps at 11.3 MBq and 18.3% for the rat-sized phantom. For the NEMA image quality phantom, the uniformity was 5.8%, and the spillover ratios measured in the water- and air-filled cold region chambers were 0.047 and 0.044, respectively. The recovery coefficients (RC) ranged from 0.31 to 0.92.These results and in vivo evaluation demonstrate that the HiPET can achieve high quality molecular imaging for biomedical applications.

High-multiplicity muon events observed with EMMA array

High-multiplicity data, collected with a segmented scintillator array of the cosmic-ray experiment EMMA (Experiment with Multi-Muon Array), is presented for the first time. The measurements were done at the depth of 75 meters (210 m.w.e.) in the Pyhäsalmi mine in Finland. EMMA uses two types of detectors: drift chambers and plastic scintillation detectors. The presented data were acquired over the period between December, 2015 and April, 2018 using 128-800 plastic scintillator pixels probing the fiducial area of ˜100 m2. The results are being interpreted in terms of CORSIKA simulations. Several events with densities in excess of 10 muons per m2 were observed. At the next stage of the analysis, the high-multiplicity events will be matched with precision tracking data extracted from the multi-layer drift chambers of EMMA. Observation of high-density muon bundles was first reported by the LEP experiments: DELPHI, L3+C, and ALEPH. More recently, the ALICE experiment at CERN has provided new cosmic-ray results together with improved interpretation benefiting from the updated cross section values extracted from LHC results. While the tracking performance of ALICE is superior to EMMA, the duration of ALICE cosmic-ray measurements is very limited. Over the period of 2010–2018 the total exposure was only 93 days while EMMA, having a similar overburden provides a larger footprint and collects data continuously.

Optimisation of monolithic nanocomposite and transparent ceramic scintillation detectors for positron emission tomography

High-resolution arrays of discrete monocrystalline scintillators used for gamma photon coincidence detection in PET are costly and complex to fabricate, and exhibit intrinsically non-uniform sensitivity with respect to emission angle. Nanocomposites and transparent ceramics are two alternative classes of scintillator materials which can be formed into large monolithic structures, and which, when coupled to optical photodetector arrays, may offer a pathway to low cost, high-sensitivity, high-resolution PET. However, due to their high optical attenuation and scattering relative to monocrystalline scintillators, these materials exhibit an inherent trade-off between detection sensitivity and the number of scintillation photons which reach the optical photodetectors. In this work, a method for optimising scintillator thickness to maximise the probability of locating the point of interaction of 511 keV photons in a monolithic scintillator within a specified error bound is proposed and evaluated for five nanocomposite materials (LaBr3:Ce-polystyrene, Gd2O3-polyvinyl toluene, LaF3:Ce-polystyrene, LaF3:Ce-oleic acid and YAG:Ce-polystyrene) and four ceramics (GAGG:Ce, GLuGAG:Ce, GYGAG:Ce and LuAG:Pr). LaF3:Ce-polystyrene and GLuGAG:Ce were the best-performing nanocomposite and ceramic materials, respectively, with maximum sensitivities of 48.8% and 67.8% for 5 mm localisation accuracy with scintillator thicknesses of 42.6 mm and 27.5 mm, respectively.

Spatial resolution of novel liquid scintillating capillary array

Scintillating array image plates are allowed high resolution through a thicker detector which increases quantum efficiency without degrading the imaging resolution substantially. Due to limitations imposed by process capability, scintillator fiber array with pixel diameter less than 0.2 mm is hardly manufactured to improve performance. Therefore, a liquid scintillator capillary array with 0.1 mm pixel is developed to improve the detection efficiency and spatial resolution of image plate for low intensity radiation imaging. Its performances are studied and tested by simulation and experiment, and are compared with those of scintillating fiber array. Especially in order to gain high fidelity representation of modulation transfer function of the array image plate, a method of simulating and measuring the slanted knife edge response and an iterative algorithm are introduced. For 14 MeV neutron and 1.25 MeV gamma, the slanted knife edge responses of these array image plates with pixel dimensions in a range from 0.1 mm to 0.5 mm are respectively simulated by MCNPx program and the modulation transfer function (MTF) are obtained. The simulation results show that compared with scintillating fiber array, the liquid scintillator capillaries array has an obvious merit in spatial resolution because of greater stopping power for secondary charged particle in the capillary quartz glass wall with 0.02 mm in thickness. Its ultimate resolution can reach to 1.8 lp/mm for 14 MeV neutron by simulation. At the 4000 Ci <sup>60</sup>Co facility, a 5-cm-thick tungsten bar, one side of which has a curvature of 0.1 radian to minimize the misalignment effect, is made a knife edge. The MTF of the scintillating fiber array with 0.3 mm and 0.5 mm pixel and newly developed liquid scintillator capillary array is measured through this tungsten knife edge. Experimental measurement results have also verified that the liquid scintillator capillary array performs well in spatial resolution and luminescent uniformity for 1.25 MeV gamma. The ultimate spatial resolution, 0.9 lp/mm is gained, and those of other scintillating fiber arrays are all less than 0.5 lp/mm. Moreover, experimental test validates the simulating method and simulated results, although the measured value is slight less than the simulated value because of the effect of dimension of <sup>60</sup>Co source.

New equipment for neutron scattering cross-section measurements at GELINA

Two new experimental setups are being developed at European Commission’s Joint Research Centre in Geel, Belgium. The scintillator array ELISA (ELastic and Inelastic Scattering Array) is for high-quality neutron scattering cross section and angular distribution measurements. It has the capability to separate neutron-and photon-induced events via pulse-shape analysis. Inelastic scattering can also be resolved from the elastic channel. The ELISA setup and data analysis procedure were validated by performing measurements using carbon and iron samples. The DELCO spectrometer (Detection of ELectrons from COnversion) is intended for inelastic neutron scattering cross-section measurements in cases where the detection of γ rays is not feasible. The current status of DELCO, results from the first tests, and future prospects will be discussed.

Short-range Lifetime Measurements for Deep-inelastic Reaction Products: the \(^{19}\)O Test Case

An experiment, aiming at measuring lifetimes of excited states in neutron-rich C and O isotopes, was performed at the GANIL laboratory with the use of the AGATA segmented HPGe tracking array, coupled to the PARIS scintillator array and to the VAMOS++ magnetic spectrometer. The nuclei of interest were populated in transfer and deep-inelastic processes induced by an 18O beam at 126 MeV (7.0 MeV/u) on a 181Ta target. This paper contains a brief description of a novel implementation of a Monte-Carlo technique, which allowed us to obtain excited states lifetimes in the range from tens to hundreds femtoseconds for a reaction with complex initial velocity distribution, making use of the Doppler-shift attenuation method (DSAM). As a test case, we present here the analysis for two states in 19O: 2371-keV 9/2 + and 2779-keV 7/2 +, for which lifetimes of τ > 400 fs and τ = 140+50 −40 fs were obtained, respectively, in agreement with literature values. This newly developed approach will be essential for short lifetimes measurements in neutron-rich systems, exploiting intense ISOL-type beams, currently under development.

Feasibility study for radionuclide identification using multi-array plastic scintillator and energy weighted algorithm of radiation portal monitors: a Monte Carlo study

Radiation portal monitor (RPM) systems have been deployed worldwide to monitor the inflow of illegal radionuclides at border crossings. Large-sized plastic scintillation detector has been widely used for RPM system, but due to the components of the plastic scintillator of low Z-number material the poor energy resolution shows the broad energy spectrum without clear photo peak identifying the radionuclides. The aim of this study is to develop an RPM based on the scintillator array for enhancing the detection efficiency and energy resolution. Using a Monte Carlo (MC) method, an RPM comprising the multi-array hexagonal scintillator was simulated with varied diameters of 8–24 cm and thicknesses of 5–25 cm, and the performance was assessed with four radionuclides of 137Cs, 60Co, 226Ra, and 40K. To determine the optimal scintillator dimensions, the generation and collection efficiency of optical photons were assessed. The performance of the multi-array scintillator was evaluated by comparing it with the conventional single scintillator in terms of the gamma-collection efficiency and the energy resolution with the full width at half maximum (FWHM) of the energy weighted spectrum. The plastic scintillator of 8 cm diameter and 15 cm thickness was determined to have the optimal dimensions out of the 25 geometry conditions. The multi-array plastic scintillator showed an increased optical photon-collection probability, up to 35% more than a conventional plastic scintillator, while the FWHM decreased by more than 20%, resulting in an improved energy resolution. Based on this MC-based design and optimization study, a proof-of-principle detection system is currently being built and an experimental study to demonstrate its superior accuracy in the identification of radionuclides will also be conducted in the future.

Design and evaluation of gapless curved scintillator arrays for simultaneous high-resolution and high-sensitivity brain PET

Brain PET scanners that simultaneously provide high-resolution across the field-of-view and high-sensitivity can be constructed using detectors based on SiPM arrays coupled to both ends of scintillator arrays with finely segmented and long detector elements. To reduce the dead space between detector modules and hence improve the sensitivity of PET scanners, crystal arrays with curved surfaces are proposed. In this paper, the performance of a proof-of-concept detector module with nine detector submodules based on SiPMs coupled to both ends of a curved LYSO array with a pitch size of 1.0 × 1.0 mm2 at the front-end and a length of 30 mm was evaluated. A simple signal multiplexing method using the shared-photodetector readout method was evaluated to identify the crystals. The results showed that all the LYSO elements in the detector module of interest could be clearly resolved. The energy resolution, depth-of-interaction resolution, and timing resolution were 14.6% ± 3.6%, 2.77 ± 0.39 mm, and 1.15 ± 0.07 ns, respectively, obtained at a bias voltage of 28.0 V and a temperature of 16.8 °C ± 0.2 °C.

Feasibility of High-Resolution PET Detector Readout by 2-D Tetra-Lateral Position-Sensitive Silicon Photomultiplier

In this paper, we present the feasibility of high-resolution PET detector readout by a 2-D tetra-lateral position-sensitive Silicon photomultiplier with an intrinsic cap resistive layer for charge division (CRL-SiPM). The scintillation imaging sensor for 511 keV gamma ray detection is realized by coupling a 5 $\times $ 5 array of 0.45 $\times $ 0.45 $ \times $ 6 mm3 LYSO crystals to the CRL-SiPM with an active area of 2.77 $ \times $ 2.77 mm2 and micro APD cell pitch of $ \sim 10~ \mu \text{m}$ . The scintillator arrays are clearly distinguished and good scintillator array imaging with little position distortion has been achieved. An energy resolution of ~13.5% and coincidence time resolution of 555 ps are demonstrated, respectively. Therefore, the potential PET imaging sensor with greatly reduced readout channels has been verified.

Investigation of the Generation of Positrons near the Threshold

The results of experimental studies of positron generation near the threshold carried out in 2018 at the ILC MSU femtosecond laser complex and the LUE-8 linear electron accelerator of the Institute for Nuclear Research of the Russian Academy of Sciences are presented. The measurements were carried out using three different detection methods: using a MEDIPIX detector; phosphor films and video cameras; as well as scintillation arrays and silicon photomultipliers.

Design and on-orbit status of the trigger system for the DAMPE mission

DArk Matter Particle Explorer (DAMPE), the first Chinese astronomical satellite, was successfully launched at the Jiuquan Satellite Launch Center on 2015 Dec. 17. DAMPE consists of four subdetectors: Plastic Scintillator array Detector (PSD), Silicon-Tungsten tracKer-converter (STK), Bismuth Germanium Oxide (BGO) imaging calorimeter and NeUtron Detector (NUD). The global hardware trigger signal, which is generated by hits from the BGO calorimeter and the trigger logic board in the data acquisition system (DAQ), is responsible for event selection and DAQ synchronization of DAMPE. On orbit, to improve the detection efficiency, different trigger logics are used for event selection in different regions of latitude. The DAMPE trigger system compresses the average on-orbit trigger rate to 60Hz and reduces science data mass to less than 13GB per day to meet the requirement for the satellite’s data link. The whole trigger system has run stably up to now, ensuring excellent on-orbit operation of DAMPE.

Development of radiation imaging system for nutrient distribution in sapling

Radioactive tracer in plant commonly uses X-ray films or imaging plate for study nutrient distribution, which cause radioactive waste. We developed a real-time imaging system for radiotracer in sapling to reduce a large number of samples and radioactive waste. The main components of the developed system consist of the radiation imaging detector, the mechanical part, and the operating software. We used 4 × 4 channel array of Silicon Photomultiplier (SiPM) model ArrayC-30035-16P from SensL coupling with plastic scintillator array of 3 × 3 × 5 mm3 pixels as a radiation imaging detector. The signals from the detector were amplified and noises discriminated then transfer to the operating software on a personal computer (PC). The area scanning unit and mechanical parts were modified from MicromakeCl 3D printer with customised control board and controlled by operating software on PC interfacing via USB to RS232. Furthermore, the LabVIEW base system control software was developed to control the movement of motors in X, Y and Z directions of the mechanical control board in associated with the counting signals transferring from the developed detector board. Each counted data from the scanning process was transformed into rainbow scale image. The developed system could measure a sample with a maximum size of 300 × 300 mm2, and the precision of motors was ± 0.1 mm. The control software is able to change parameters of the time for counting, a pitch of motors and scanning area of a sample. Finally, the developed system was tested by run through the process of radiotracer in the maize sapling growth for 30 hours. The result showed satisfactory rainbow color scale image of accumulation and distribution of radioactive tracer in sapling.

Measurements of fast neutron scattering in plastic scintillator with energies from 20 to 200 MeV

Scattering of neutrons with energies ranging from 20 to 200 MeV was observed in an organic plastic scintillator array as a test for accuracy of simulation by two GEANT4-based models. The experiment was conducted at the LANSCE WNR facility at Los Alamos National Laboratory using a collimated neutron beam of well-defined energy and trajectory impinging on 16 BC-408 plastic scintillator detectors arranged in a horizontal array 2 detectors tall and 8 deep. Results from neutron scattering observations include hit-multiplicity distributions, beam attenuation depth, crosstalk events, scattering angle, attenuation depth between hits, and dark-scattering of neutrons from carbon nuclei, all as a function of the incident neutron energy. Measurement results are compared with predictions from two GEANT4-based Monte Carlo simulations, and agreement varies considerably over neutron energy, becoming poor at higher energies, pointing to needed improvement in simulation of neutrons in plastic scintillator.