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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

From Detector Layout to Signal Analysis: Geometry Optimization and Neutron-Gamma Tagging in Plastic Scintillator Detectors

Neutrinos are elementary particles with many properties still unknown. Their masses so far have only upper and lower limits. Still, due to neutrino oscillations, it is clear that they are not massless, as stated by the Standard Model of Elementary Particles. Neutrinos are also present in the Universe in vast amounts, but they rarely interact with the surrounding matter. Their abundance makes them very interesting for many theories beyond the Standard Model, e.g., dark matter searches and CP symmetry violation in the leptonic sector, which could be (partially) responsible for the observed matter-antimatter asymmetry in today's Universe.\\ The Deep Underground Neutrino Experiment (DUNE) is a next-generation accelerator-based neutrino oscillation experiment that will study neutrinos with unprecedented precision and may answer many open questions. DUNE uses a powerful neutrino beam from Fermilab. It consists of a Near Detector (ND) complex to measure neutrinos before oscillat ion, and a Far Detector (FD) complex $1300\ \mathrm{km}$ away to measure them after oscillation. As part of the ND complex, measurements are also possible with different angles to the neutrino beam. This enables excellent control of systematic uncertainties of e.g., neutrino cross section measurements.\\ One detector in the near detector complex is The Muon Spectrometer (TMS), an extension of a Liquid Argon (LAr) detector that measures the charge and momentum of muons produced in neutrino interactions within the LAr. The design of this detector, which consists of alternating layers of steel and plastic scintillator bars, must be optimized for the expected muon energies.\\ In this thesis, a study of the optimal module orientation plan is presented, which is necessary for the physics performance of the near detector complex and, by extension, DUNE. As part of this study, the event reconstruction was also developed and improved. Simulated muons are then reconstructed, and the performan ce of different module orientation plans is tested.\\ As a second part, a study of neutron and gamma tagging using a Pulse Shape Discriminating (PSD) plastic scintillator is presented. The properties of this material allow particle differentiation based on the temporal distribution of emitted light. A novel approach to using the individual light signals was successfully tested using data from a small, local test setup.

Nehm, Asa [Mainz U.]↗
DOE OSTI2022

Plastic Scintillators via Rapid Photoinitiated Cationic Polymerization of Vinyltoluene

Cationic photopolymerization is applied for the rapid curing of a vinyltoluene and fluorophore solution into an efficient plastic scintillator. A hard solid is obtained via UV light-initiated polymerization of vinyltoluene, diaryliodonium salt, 9,9-dimethyl-2-phenylfluorene (PhF), and 9,9-dimethyl-2,7-distyrlfluorene (SFS) at ambient conditions with high conversion rates under a range of cationic photoinitiator concentrations, fluorophore concentrations, and light intensities. Insight into photopolymerization kinetics via photo differential scanning calorimetry (photoDSC) revealed photocuring time scales similar to those achieved in a commercial 3D printing resin. Furthermore, scintillator samples prepared cationically performed well compared to samples of equivalent compositions prepared by a lengthy thermally initiated radical polymerization.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Investigation of a digitizer for the plastic scintillation detectors of time-of-flight mass measurements

A CAEN DT5742 digitizer has been investigated to process the fast signals from the photomultiplier tubes of the time-of-flight detectors for fast ion beams. A test setup consisting of two plastic scintillation detectors and a pulsed laser source provided signals which were recorded by the digitizer and systematically analyzed with different algorithms to derive the amplitude, rise time and arrival time of the detection signal. To obtain the best amplitude and time resolutions, various optimization techniques including peak fitting and signal smoothing, interpolation improvement, and time-walk correction by amplitude and rise time have been performed and compared in detail. Here we compared the time resolutions obtained by three digital algorithms of leading-edge, zero-crossing constant-fraction (ZC-CFD) and direct constant-fraction discriminations. Finally, we found that the best time-of-flight resolution between two PMTs can be achieved as 12 ps by the method using sample minimum for peak location and using the time-walk-resistant ZC-CFD with 4-point interpolation for timing.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Lineshape response of plastic scintillator to pair production of 4.44 MeV γ’s

We measure the distribution of energy deposited in a 40 × 88 mm plastic scintillator by e + e – pair production of 4.44 MeV γ-rays. He, we observe the double-escape peak of 3.42 MeV from pair production by tagging 511 keV annihilation radiation in two high-Z scintillators. The source is a standard commercial neutron source using α-emitting 241 Am encapsulated with 9 Be, which has a reaction branch feeding the first I π = 2 + state of 12 C making the 4.44 MeV γ-rays. We demonstrate the extraction of the double-escape peak from the large neutron-produced backgound, and explore some of the features and difficulties of this technique with our apparatus.

Beta calibration↗
DOE OSTI2025

The effect of radiation damage on the light yield and uniformity of candidate plastic scintillator tiles for the CMS hadron calorimeter upgrade

A study has been performed to understand the effects of radiation damage on various plastic scintillator tiles considered for a possible upgrade of the hadron calorimeter of the CMS detector. Measurements were made with unirradiated tiles and with tiles that had been irradiated in the CMS collision hall to a dose of 44 kGy. Results are presented for the tiles of different shapes in terms of the energy spectrum, efficiency as a function of the position at which each tile was hit, as well as light yield. All the tiles showed a light reduction of up to about 50%. The tiles with the shape currently used in the CMS detector did not see increased non-uniformity of light collection, while a significant disuniformity was observed for the tiles considered as alternatives.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Prototype reactor-antineutrino detector based on 6 Li-doped pulse-shape-discriminating plastic scintillator

An aboveground 60-kg reactor-antineutrino detector prototype, comprising a two-dimensional array of 36 6 ⁢Li-doped pulse-shape-sensitive plastic scintillator bars, is described. Each bar is 50 cm long with a square cross section of 5.5 cm. Doped with 6 ⁢Li at 0.1% by mass, the detector is capable of identifying correlated energy depositions for the detection of reactor antineutrinos via the inverse-𝛽-decay (IDB) reaction. Each bar is wrapped with a specular reflector that directs photons toward photomultiplier tubes mounted at both ends of the bar. Here, this paper highlights the construction, key features, and main performance characteristics of the system. The system, which relies on multiple observables such as pulse-shape discrimination, energy, position, and timing, is capable of detecting IBD-like neutron-correlated backgrounds, long-lived decay chains, and cosmogenic isotopes.

Physics↗
DOE OSTI2023

Fast-, Light-Cured Scintillating Plastic for 3D-Printing Applications

Additive manufacturing techniques enable a wide range of possibilities for novel radiation detectors spanning simple to highly complex geometries, multi-material composites, and metamaterials that are either impossible or cost prohibitive to produce using conventional methods. The present work identifies a set of promising formulations of photocurable scintillator resins capable of neutron-gamma pulse shape discrimination (PSD) to support the additive manufacturing of fast neutron detectors. The development of these resins utilizes a step-by-step, trial-and-error approach to identify different monomer and cross-linker combinations that meet the requirements for 3D printing followed by a 2-level factorial parameter study to optimize the radiation detection performance, including light yield, PSD, optical clarity, and hardness. The formulations resulted in hard, clear, PSD-capable plastic scintillators that were cured solid within 10 s using 405 nm light. The best-performing scintillator produced a light yield 83% of EJ-276 and a PSD figure of merit equaling 1.28 at 450–550 keVee.

Frandsen, Brian G. (ORCID:0000000319964320)↗
DOE OSTI2025

Assessment of Thin Plastic Scintillation Detectors for Beta-Particle Measurements at the Advanced Test Reactor Critical Facility

The Fission Wire Measurement System is a custom measurement system designed in the 1960s to measure the beta-particle activity of irradiated uranium-aluminum fission wires. This measurement is conducted to determine the fission rate profile of the Advanced Reactor Test Critical facility. The Advanced Test Reactor Critical facility is an open-pool, low-power test reactor used to qualify experiment configurations and verify core models prior to full-power experiment irradiations in the Advanced Test Reactor. Power distribution measurements in ATR-C use uranium-aluminum wires that are distributed throughout the core to validate simulation and modeling results. These measurements require from 340 to 1500 wires to be irradiated and measured within a 12-hour window. The system consists of 4 measurement channels and one reference channel, each with a 2-pi proportional gas flow detector and the measurement channels each have an automated sample changer. The gas flow detectors are of a custom design for this detector system that use methane gas with a large anode wire compared to modern proportional counters. These detectors, which are nearly 60 years old are irreplaceable. The measurements from these gas detectors are affected by the gas flow rate, atmospheric and line pressure, and are very sensitive to the applied high voltage. Recent improvements have been made to the control and data acquisition system, but the detectors have remained the same. The nature of the measurement of the fission product decay activity is such that the energy spectrum of the signal is changing with time. Thin, 250-um thick, plastic scintillators were commercially obtained as a potential replacement for the gas flow detectors. The original calibration of the uranium-aluminum fission wires was conducted in 1965 using a series of irradiations of gold foils and the wires in a well-characterized thermal neutron field. These measurements provided a time-dependent fission rate conversion factor from the gold foil data to calibrate the fission wires based on the response from the 2-pi proportional gas detectors. Transitioning to the new detectors requires qualification and testing. The sensitivity of the scintillators to changes in the energy spectrum of the fission wires and translation of the calibration factor have been completed. These measurements indicated that the sensitivity of the scintillators over time changes at a different rate than the sensitivity of the gas flow detectors. However, the inverse activity of measurements of both detector types is linear with time. Initial results indicate that the scintillator detectors will be a sufficient replacement for the gas detectors with minor adjustments to the fission rate conversion factor. Replacement of the detectors will improve the fission wire measurements and provide a more stable and reliable measurement system.

46 - INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AN↗
DOE OSTI2022

Assessment of the Imaging Properties of Plastic Scintillators at FP60R for Neutron Imaging Applications [Slides]

4mm thick Stilbene gives the brightest signal but at the cost of resolution. 1 and 2 cm BC412 gave the highest resolution images. The HI-LY scintillator is better suited for DD neutrons. Future work includes: measurements this summer using an event-mode imaging camera which promises sub-pixel resolution through center-of-mass techniques, opportunities for DD neutron tests during laser-driven z-pinch experiments at UNR, and assess scatter within scintillator.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Compounds and composition for preparation of lithium-loaded plastic scintillators

A scintillator material includes a polymer matrix, a primary dye in the polymer matrix, the primary dye being a fluorescent dye; a secondary dye, and a Li-containing compound in the polymer matrix, where the Li-containing compound is a Li salt of a short-chain aliphatic acid. In addition, the scintillator material exhibits an optical response signature for thermal neutrons that is different than an optical response signature for fast neutrons.

Zaitseva, Natalia P.↗
DOE OSTI2023

Manufacturing and characterization of a boron-loaded fast-cured plastic organic scintillator

A novel fast-cured, boron-loaded, plastic organic scintillator was developed and characterized. A diisopropylnaphthalene-containing scintillator was manufactured in minutes with the addition of two commercially available fast-curing monomers, isobornyl acrylate (IBOA) and 1,6-Hexanediol dimethacrylate (HDDMA). Further, the light yield of the device was measured to be approximately 70% relative to a similarly sized, but several-year-aged, EJ-276 detector. Using a coincidence capture technique, the neutron capture light output was found to be 87.7 ± 4.2 keVee, which was 1.47 ± 0.07 greater than the light output from a 59.5 keV electron. Producing a viable fast-cured and thermal-neutron-sensitive detector enables the capability to pursue cost-effective 3D printed thermal neutron detectors in a timely manner.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Scintillator ageing of the T2K near detectors from 2010 to 2021

The T2K experiment widely uses plastic scintillator as a target for neutrino interactions and an active medium for the measurement of charged particles produced in neutrino interactions at its near detector complex. Over 10 years of operation the measured light yield recorded by the scintillator based subsystems has been observed to degrade by 0.9–2.2% per year. Extrapolation of the degradation rate through to 2040 indicates the recorded light yield should remain above the lower threshold used by the current reconstruction algorithms for all subsystems. This will allow the near detectors to continue contributing to important physics measurements during the T2K-II and Hyper-Kamiokande eras. Additionally, work to disentangle the degradation of the plastic scintillator and wavelength shifting fibres shows that the reduction in light yield can be attributed to the ageing of the plastic scintillator. The long component of the attenuation length of the wavelength shifting fibres was observed to degrade by 1.3–5.4% per year, while the short component of the attenuation length did not show any conclusive degradation.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Characterization of PIPS detectors for measurement of radioxenon

The International Monitoring System arm of the Comprehensive Nuclear-Test-Ban Treaty Organization utilizes sampling of atmospheric radioxenon to scan the world for nuclear testing events. Current designs utilized in the field involve plastic scintillator cells run in coincidence with Sodium Iodide (NaI) or High Purity Germanium (HPGe) detectors. The use of plastic scintillators as electron detectors exhibit some issues in comparison to other materials. Silicon detectors are analyzed as an alternative to plastic scintillators for beta detection based on their higher energy resolution and lowered memory effect. A radioxenon detection setup was created with the intent of measuring radioxenon samples using coincidence counting between silicon and NaI detectors as well as silicon and HPGe. Finally, the absolute efficiency of both setups is calculated and compared.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2024

Commissioning a time-gated camera for fast neutron beamline spatial-energy characterization at LANSCE-WNR spallation source

An energy-resolved fast neutron beam imaging diagnostic has been successfully commissioned at the Weapons Neutron Research (WNR) spallation source within the Los Alamos Neutron Science Center (LANSCE) facility. This diagnostic replaces the existing analog phosphor image plates, which integrate across all neutron energies, as well as other particles, with a near-real-time energy-sensitive imaging capability. The system uses a fast plastic scintillator coupled with an intensified CCD camera. Specifically, the Teledyne Pi-MAX4 camera is coupled with either a 4 mm thick Eljen (EJ) 204 or 228 plastic scintillator. These scintillators are most sensitive to the fast neutrons (0.8-800 MeV) directly from the spallation source rather than low energy background radiation. Experimentally, these plastic scintillators were shown to have sufficiently fast decay to differentiate the bright gamma flash from the spallation neutrons. The spatial resolution is dominated by neutron beam divergence, with minimal additional contributions from scatter and light divergence. The system successfully resolved changes in neutron beam characteristics caused by intentional proton steering variations. Additionally, simulations of scintillator light yield as a function of thickness conducted using PHITS (with Scinful-QMD package) found that increasing scintillator thickness from 4 mm to 6 or 8 mm could potentially increase brightness ~ 3x. This may be explored if there is a need to reduce image acquisition time from several minutes to under one minute.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗