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All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Transparent plastic scintillators for neutron detection based on lithium salicylate

Transparent plastic scintillators with pulse shape discrimination containing 6 Li salicylate have been synthesized by bulk polymerization with a maximum 6 Li loading of 0.40 wt%. Photoluminescence and scintillation responses to gamma-rays and neutrons are reported in this paper. Plastics containing 6 Li salicylate exhibit higher light yields and permit a higher loading of 6 Li as compared to previously reported plastics based on lithium 3-phenylsalicylate. However, pulse shape discrimination performance is reduced in lithium salicylate plastics due to the requirement of adding more nonaromatic monomers to the polymer matrix as compared to those based on lithium 3-phenylsalicylate. Finally, reduction in light yield and pulse shape discrimination performance in lithium-loaded plastics as compared to pulse shape discrimination plastics without lithium is interpreted in terms of energy transfer interference by the aromatic lithium salts.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Evaluation of neutron light output response functions in EJ-309 organic scintillators

An accurate model of the nonlinear detector response of organic scintillators to neutrons is required to correctly simulate fast neutron detection, as well as interpret measured pulse height data. Several empirical and semi-empirical models are available to fit measured scintillator light output data. In this work, EJ-309 light output data from neutrons depositing 1.15–5.15 MeV on hydrogen were analyzed using empirical models as well as semi-empirical models based on the work of Birks and Voltz. Although all tested models fit the experimental light output data well in the measured range, the models were observed to diverge in low-energy extrapolation. The models were then tested by comparing a measurement and MCNPX-PoliMi simulation of an EJ-309 detector response to fast neutrons from a 252 Cf spontaneous fission source. The agreement between the measured and simulated pulse height distributions varied significantly depending on the light output model used. The best agreement between simulated and measured neutron pulse height distributions was achieved by using the Birks model. The bin-by-bin agreement was better than 5% over the range 0.08–2.18 MeVee, and better than 10% from 2.18 to 3.13 MeVee. Furthermore, the integral count rate over the range 0.08–3.14 MeVee differed by less than 1% in absolute units.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Radionuclide identification algorithm for organic scintillator-based radiation portal monitor

We have developed an algorithm for on-the-fly radionuclide identification for radiation portal monitors using organic scintillation detectors. The algorithm was demonstrated on experimental data acquired with our pedestrian portal monitor on moving special nuclear material and industrial sources at a purpose-built radiation portal monitor testing facility. The experimental data also included common medical isotopes. The algorithm takes the power spectral density of the cumulative distribution function of the measured pulse height distributions and matches these to reference spectra using a spectral angle mapper. F-score analysis showed that the new algorithm exhibited significant performance improvements over previously implemented radionuclide identification algorithms for organic scintillators. Reliable on-the-fly radionuclide identification would help portal monitor operators more effectively screen out the hundreds of thousands of nuisance alarms they encounter annually due to recent nuclear-medicine patients and cargo containing naturally occurring radioactive material. Lastly, portal monitor operators could instead focus on the rare but potentially high impact incidents of nuclear and radiological material smuggling detection for which portal monitors are intended.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Construction and response of a highly granular scintillator-based electromagnetic calorimeter

Here, a highly granular electromagnetic calorimeter with scintillator strip readout is being developed for future linear collider experiments. A prototype of 21.5 X 0 depth and 180 × 180 mm 2 transverse dimensions was constructed, consisting of 2160 individually read out 10 × 45 × 3 mm 3 scintillator strips. This prototype was tested using electrons of 2–32 Ge V at the Fermilab Test Beam Facility in 2009. Deviations from linear energy response were less than 1.1%, and the intrinsic energy resolution was determined to be ( 12 . 5 ± 0 . 1 ( stat. ) ± 0 . 4 ( syst. ) ) % / E [ Ge V ] ⊕ ( 1 . 2 ± 0 . 1 ( stat. ) - 0 . 7 + 0 . 6 ( syst. ) ) % , where the uncertainties correspond to statistical and systematic sources, respectively.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Predictive model of scintillator plastic fogging in portals

We have developed a science-based predictive model for fogging of the scintillator plastics deployed in radiation portal monitors. The only input required is the weather conditions [i.e., daily high and low, for temperature and relative humidity (R.H.)]. The code utilizes this information, together with a thermodynamic model of the water content in equilibrium with the plastic surface, a diffusion model of the water transport into the interior of scintillator plastic panel, and a comparison of the resulting paired “water-content/night-temperature” points as a function of position in the panel against an empirical “fog-line” that establishes a water/temperature criterion for the onset of fogging. In conclusion, we have analyzed the behavior of several representative portal monitor sites, and the output of the model analysis is reasonably consistent with observation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Improving light yield measurements for low-yield scintillators

Light power spectra are introduced as a new tool for relative light yield (LY) determinations. Light event spectra have commonly been used for this purpose. Theoretical background supporting this change is provided. It is shown that the derivative of a light power spectrum can provide a reliable LY measurement at levels as low as 2% of those for high-yield liquid scintillators. In this work, applications to light evolution in the PPO+LAB system and to water-based liquid scintillators are described.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

A helical-shape scintillating fiber trigger and tracker system for the DarkLight experiment and beyond

The search for new physics beyond the Standard Model has interesting possibilities at low energies. For example, the recent 6.8σ anomaly reported in the invariant mass of e + e - pairs from 8 Be nuclear transitions and the discrepancy between predicted and measured values of muon g-2 give strong motivations for a protophobic fifth-force model. At low energies, the electromagnetic interaction is well understood and produces straightforward final states, making it an excellent probe of such models. However, to achieve the required precision, an experiment must address the substantially higher rate of electromagnetic backgrounds. Here in this paper, we present the results of simulation studies of a trigger system, motivated by the DarkLight experiment, using helical-shape scintillating fibers in a solenoidal magnetic field to veto electron–proton elastic scattering and the associated radiative processes. We also assess the performance of a tracking detector for lepton final states using scintillating fibers in the same setup.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Positron annihilation lifetime spectroscopy using fast scintillators and digital electronics

Positron Annihilation Lifetime Spectroscopy (PALS) is a non-destructive radiological technique widely used in material science studies. PALS typically relies on an analog coincidence measurement setup and allows the estimate of the positron lifetime in a material sample under investigation. The positron trapping at vacancies in the material results in an increased positron lifetime. In this work, we have developed and optimized a PALS experimental setup using organic scintillators, fast digitizers, and advanced pulse processing algorithms. We tested three pairs of different organic scintillators: EJ-309 liquid, EJ-276 newly developed plastic, and BC- 418 plastic, and optimized the data processing parameters for each pair separately. Our high-throughput data analysis method is based on single-pulse interpolation and a constant fraction discrimination (CFD) algorithm. The setup based on the BC-418 detector achieved the best time resolution of 198.3 ± 0.8 ps. We used such optimized setup to analyze two single-crystal quartz samples and found lifetimes of 161 ± 4 ps, 343 ± 12 ps and 1.34 ± 0.05 ns, in good agreement with the characteristic time constants of this material. The proposed experimental set up achieves a time resolution comparable to the minimum positron lifetime in quartz, which makes it possible to accurately characterize material vacancies by discriminating between the lifetimes of either the spin singlet or triplet states of positronium. The optimized data processing algorithms are relevant to all the applications where fast timing is important, such as nuclear medicine and radiation imaging

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Plastic scintillation detectors for time-of-flight mass measurements

Fast timing detectors are an essential element in the experimental setup for time-of-flight (ToF) mass measurements of unstable nuclei. We have upgraded the scintillator detectors used in experiments at the National Superconducting Cyclotron Laboratory (NSCL) by increasing the number of photomultiplier tubes that read out their light signals to four per detector, and characterized them in a test experiment with 48 Ca beam at the NSCL. The new detectors achieved a time resolution (σ) of 7.5 ps. We systematically investigated different factors that affect their timing performance. In addition, we evaluated the ability of positioning the hitting points on the scintillator using the timing information and obtained a resolution (σ) below 1 mm for well-defined beam spots.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Crystal growth and scintillation properties of pure and Tl-doped Cs 3 Cu 2 I 5

Here, the Bridgman crystal growth and scintillation properties of both undoped and Tl-doped Cs 3 Cu 2 I 5 are presented. This material is very attractive for gamma and X-ray detection applications, with a density of 4.53 g/cm 3 and effective atomic number of 51.9. Undoped Cs 3 Cu 2 I 5 had a light yield of 41,500 photons/MeV, with an energy resolution of 4.4% at 662 keV. Thallium doping at 0.5 mol % resulted in a much-improved scintillation response, in which light yield increased to 98,200 photons/MeV and energy resolution reduced to 3.3% at 662 keV. The X-ray excited emission is centered at 442 nm for the undoped and 500 nm for the Tl-doped crystals. The undoped emission is broad, typical of excitonic emission, while thallium doping results in an even broader band with features of both the undoped and thallium defect-mediated emissions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Characterization of retroreflective tape optical properties for use with position-sensitive scintillator detectors

Reflective materials such as Teflon and Enhanced Specular Reflector are commonly used to maximize light collection in scintillator-based radiation detection systems. While effective, in most cases, the spatial information carried by the light is diminished or lost entirely. Retroreflectors, in contrast, better preserve the spatial information and have been shown to improve the localization performance of such systems. In this work, the relative retroreflectivity of a selection of commercial retroreflective tapes and their performance impact when coupled to a plastic scintillator are reported. Finally, we demonstrate improved localization performance with some tapes compared to Teflon and black paint.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

A 90 ° bend curved light-guide for TOF scintillating detectors

We report here a bench study of TOF resolution using a 90° bend curved solid light-guide (LG) used to transport the light from a plastic scintillator counter to a photomultiplier (PMT). The 90° LG allows the rotation of the PMT axis to be vertical to the detector axis, in an environment featured by a strong magnetic field along the detector surface, or other geometrical constrains. We show that with a TOF counter of 2000 x 100 x 60 mm 3 and light read-out by PMTs at its two 100 × 60 mm 2 sides, when 90° LG benders are used between the scintillating bar and the PMTs on both sides, the TOF resolution is worsen, by 5–10%.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Monte Carlo calculations of the extraction of scintillation light from cryogenic $N$-type GaAs

We report the high scintillation luminosity of n-type GaAs at 10 °K is surprising because (1) with a refractive index of 3.5, escape is inhibited by total internal reflection and (2) narrow-beam experiments at 90 °K report infrared absorption coefficients of several per cm. This paper presents Monte Carlo calculations showing that the high luminosity at 10 °K can be explained if (1) the narrow-beam absorption is almost all optical scattering and (2) the absolute absorption coefficient is below 0.1 per cm. Sixteen surface reflector configurations are simulated for a range of internal scattering and absolute absorption coefficients, and these can guide the design of cryogenic scintillating GaAs targets for the direct detection of dark matter. The discussion section presents a possible infrared scattering mechanism based on the metallic nature of n-type GaAs. A supplement file describes (1) the Monte Carlo program steps in detail and (2) how narrow-beam and integrating sphere experiments can measure the cryogenic optical scattering and absolute absorption coefficients.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

New method for level-lifetime measurements with thick scintillators

Level lifetimes provide key insight into the structure of atomic nuclei and serve as stringent tests of theoretical descriptions. Though several methods for determining level lifetimes exist for both reaction measurements and decay studies, here the focus is on techniques involving the direct measurement of time differences between population and subsequent depopulation of excited states. The techniques presented herein are broadly applicable across multiple timing ranges, but the approach is specifically described for the βγ timing method. A multi-step, amplitude-dependent time walk correction was employed to address the data analysis complications that arise from using thick scintillators for electron detection. Further, additional corrections for the depth of the interaction must also be performed when the parent isotope has been implanted into the detector. Techniques are presented for performing these time walk and depth of interaction corrections. Subsequently, a new Monte Carlo method utilizing measured detector responses obtained from the data, coupled with chi-square minimization, is presented for extracting excited state lifetimes ≳ 100 picoseconds. The framework of this Monte Carlo method is developed for the decay of a state in 68 Zn with a known 1.6 ps half life, which is considered prompt given the detection sensitivity of the technique, and then benchmarked using two other excited states in neutron-rich Ni isotopes with 120(34) ps and 1.05(3) ns half lives. Using this new method which takes into account the thick scintillator used, these same half lives were measured to be 135(10) ps and 1.04(24) ns, respectively. The overall good agreement demonstrates the validity of the technique.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Characterization of the optical model of the T2K 3D segmented plastic scintillator detector unit cube

The magnetized near detector (ND280) of the T2K long-baseline neutrino oscillation experiment has been recently upgraded aiming to satisfy the requirement of reducing the systematic uncertainty from measuring the neutrino–nucleus interaction cross section, which is the largest systematic uncertainty in the search for leptonic charge-parity symmetry violation. A key component of the upgrade is SuperFGD, a 3D segmented plastic scintillator detector made of approximately 2,000,000 optically-isolated 1 cm 3 cubes. The SuperFGD cube unit shows promising optical performance, including a high light yield of about 40 photoelectrons (p.e.) per channel, a low cube-to-cube crosstalk rate below 3%, and a sub-nanosecond time resolution of 0.96 ns. By combining tracking and stopping power measurements of final state particles, this novel detector enables precise 3D-imaging of GeV neutrino interactions with reduced systematic uncertainties. A detailed Geant4 based optical simulation of the SuperFGD building block, i.e. a plastic scintillating cube read out by three wavelength shifting fibers, has been developed and validated with the different datasets collected in various beam tests. In this manuscript the description of the optical model as well as the comparison with data are reported.

Neutrino oscillations↗
DOE OSTI2025

Benchmarking fast-neutron response of 7 Li-enriched C 7 LYC scintillators: Simulations and experiment

New insights into the fast neutron response of 7 Li-enriched C 7 LYC scintillators have been obtained through detailed Geant4 simulations of 35 Cl(n,p) and 35 Cl(n, α) reactions that are primarily responsible for the fast neutron response of C 7 LYC. The light output of a 1” x1” C 7 LYC detector was simulated using the Birks equation for light quenching in scintillators. The simulations were benchmarked against neutron scattering data from a 12 C target obtained with a white neutron beam at the Los Alamos LANSCE facility and fourteen 1”x1” C 7 LYC detectors. Incident neutron energies extracted from time-of-flight measurements, and appropriate recoil corrections for the different detector angles were used to map the response of C 7 LYC to mono-energetic neutrons. Resonances in the 35 Cl(n,p) reaction cross-section below 3 MeV incident neutron energy were directly observed in C 7 LYC. The experimental data and simulations are compared with ENDF databases, as well as recent direct cross-section measurements of neutrons scattered from a 35 Cl target. In conclusion, the results suggest a scrutiny of the 35 Cl(n,p) and 35 Cl(n, α) cross sections at low energy in the ENDF library.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Crystal growth, scintillation properties & fast neutron-gamma discrimination of cubic halide perovskite CsCaCl 3 :(Eu 2+ , Tl + )

The vast variety of nuclear security applications require radiation detection materials tailored to their operational needs. A scintillator’s properties are strongly influenced by the choice of luminescent dopant, which facilitates customization to different applications. In this work, transparent Ø12 mm single crystals of undoped CsCaCl 3 , CsCaCl 3 :1% Eu, CsCaCl 3 :1% Tl, and CsCaCl 3 :1% Eu, 1% Tl were grown via the Vertical Bridgman method. Their scintillation properties and fast neutron-gamma discrimination capabilities were investigated. Undoped CsCaCl 3 had a light yield of 2,500 ph/MeV, which is the highest reported to date for this CVL material. The incorporation of Eu 2+ or Tl + into CsCaCl 3 as luminescence centers resulted in significantly higher light yields of ∼16,000 ph/MeV and energy resolutions of ∼8% at 662 keV. Compared to the single dopant counterparts, CsCaCl 3 :Eu, Tl had significantly suppressed afterglow; however, this came at the cost of reduced light yield. Among the materials tested, only CsCaCl 3 :Tl showed effective fast neutron and gamma discrimination capabilities, achieving a Figure of Merit of 3.2 between gamma-rays and fast neutron captures that produce protons and 1.6 between gamma-rays and fast neutron captures that produce alpha particles.

crystal growth↗
DOE OSTI2025

Scintillator based nuclear photovoltaic batteries for power generation at microwatts level

A nuclear photovoltaic battery uses scintillator to convert radiation into visible light, which is then collected by a photovoltaic (PV) cell to generate electricity. If the radiation is gamma-rays emitted from external sources, the battery may also be referred as gammavoltaic battery. In this study, a polycrystalline CdTe solar cell was optically coupled with a 2.0 cm × 2.0 cm × 1.0 cm Gadolinium Aluminum Gallium Garnet (GAGG) scintillator, and the resulting device was tested using intense gamma radiation fields from a Cs-137 (1.5 kRad/h) and a Co-60 (10 kRad/h) irradiator. Measurements with Cs-137 provided a maximum power output (P max ) of ~288 nW, with a short-circuit current density (J sc ) of ~1.22 μA/cm 2 and an open-circuit voltage (V oc ) of ~0.34 V. In contrast, Co-60 irradiator gave a P max of 1.5 μW, with a J sc of ~4.73 μA/cm 2 and a V oc of ~0.38 V. The CdTe was also paired with a Lutetium-Yttrium Oxyorthosilicate (LYSO) crystal and tested with the Cs-137 source. The experiment presents a scalable option to reach to higher power outputs by harvesting gamma radiation fields in many cases where high radiation field demands heavy shielding and is often regarded as unwanted waste.

25 ENERGY STORAGE↗