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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Characterization of stilbene-d 12 for neutron spectroscopy without time of flight

In this work, we have experimentally characterized the light-output response of a deuterated trans-stilbene (stilbene-d 12 ) crystal to quasi-monoenergetic neutrons in the 0.8 to 4.4 MeV energy range. These data allowed us to perform neutron spectroscopy measurements of a DT 14.1 MeV source and a 239 PuBe source by unfolding the impinging neutron spectrum from the measured light-output response. The stilbene-d 12 outperforms a 1 H-stilbene of similar size when comparing the shape of the unfolded spectra and the reference ones. These results confirm the viability of non-hygroscopic stilbene-d 12 crystal for direct neutron spectroscopy without need for time-of-flight measurements. This capability makes stilbene-d 12 a well suited detector for fast-neutron spectroscopy in many applications including nuclear reaction studies, radiation protection, nuclear non-proliferation, and space travel.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

A study of radiation tolerance in optical cements

We study the effect ionizing radiation has on light transmission in the wavelength range 190–1100 nm for a number of optically clear epoxies. We find that the transmittance of traditional, commercially available, optical epoxies show significant degradation for exposures of 1×10 12 MIPs/cm 2 . Degradation of light transmission progresses from the shortest wavelengths at low doses to longer wavelengths as the dose increases. In epoxy joints that are 0.1 mm thick, we observe that more than 5% of the light is lost for wavelengths less than 400 nm for traditional optical epoxies. Our studies have identified an optically clear epoxy that shows little degradation for radiation exposures up to 5.9× 10 14 MIPs/cm 2 (≈ 220 kGy).

Radiation-hard detectors↗
DOE OSTI2023

Energy calibration of germanium detectors for the Majorana Demonstrator

The Majorana Demonstrator was a search for neutrinoless double-beta decay (0νββ) in the 76 Ge isotope. It was staged at the 4850-foot level of the Sanford Underground Research Facility (SURF) in Lead, SD. The experiment consisted of 58 germanium detectors housed in a low background shield and was calibrated once per week by deploying a 228 Th line source for 1 to 2 hours. The energy scale calibration determination for the detector array was automated using custom analysis tools. We describe the offline procedure for calibration of the Demonstrator germanium detectors, including the simultaneous fitting of multiple spectral peaks, estimation of energy scale uncertainties, and the automation of the calibration procedure.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Spatial and temporal evaluations of the liquid argon purity in ProtoDUNE-SP

Liquid argon time projection chambers (LArTPCs) rely on highly pure argon to ensure that ionization electrons produced by charged particles reach readout arrays. ProtoDUNE Single-Phase (ProtoDUNE-SP) was an approximately 700-ton liquid argon detector intended to prototype the Deep Underground Neutrino Experiment (DUNE) Far Detector Horizontal Drift module. It contains two drift volumes bisected by the cathode plane assembly, which is biased to create an almost uniform electric field in both volumes. The DUNE Far Detector modules must have robust cryogenic systems capable of filtering argon and supplying the TPC with clean liquid. This paper will explore comparisons of the argon purity measured by the purity monitors with those measured using muons in the TPC from October 2018 to November 2018. A new method is introduced to measure the liquid argon purity in the TPC using muons crossing both drift volumes of ProtoDUNE-SP. For extended periods on the timescale of weeks, the drift electron lifetime was measured to be above 30 ms using both systems. A particular focus will be placed on the measured purity of argon as a function of position in the detector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Lifetime study of the ColdADC for the Deep Underground Neutrino Experiment

ColdADC is a custom ASIC digitizer implemented in 65 nm CMOS technology using specialized techniques for long-term reliability in cryogenic environments. ColdADC was developed for use in the DUNE Far Detector complex, which will consist of four liquid argon time projection chambers. Each contains 17 kilotons liquid argon as the target material in order to measure neutrino oscillations. Approximately 40,000 ColdADC ASICs will be installed for DUNE in the first two large detectors and will be operated at cryogenic temperatures during the experiment without replacement. The lifetime of the ColdADC is a critical parameter affecting the data quality and physics sensitivity of the experiment. A measurement of the lifetime of the ColdADC was carried out, and the results shown in this paper assure orders of magnitude longer lifetime of the ColdADC than the planned operation time of the detectors.

Front-end electronics for detector readout↗
DOE OSTI2025

Introducing a Markov chain-based time calibration procedure for multi-channel particle detectors: application to the SuperFGD and ToF detectors of the T2K experiment

Inter-channel mis-synchronisation can be a limiting factor to the time resolution of high performance timing detectors with multiple readout channels and independent electronics units. In these systems, time calibration methods employed must be able to efficiently correct for minimal mis-synchronisation between channels and achieve the best detector performance. We present an iterative time calibration method based on Markov Chains, suitable for detector systems with multiple readout channels. Starting from correlated hit pairs alone, and without requiring an external reference time measurement, the method solves for fixed per-channel offsets, with precision limited only by the intrinsic single-channel resolution. A mathematical proof that the method is able to find the correct time offsets to be assigned to each detector channel in order to achieve inter-channel synchronisation is given, and it is shown that the number of iterations to reach convergence within the desired precision is controllable with a single parameter. Numerical studies are used to confirm unbiased recovery of true offsets. Finally, the application of the calibration method to the Super Fine-Grained Detector (SuperFGD) and the Time of Flight (TOF) detector at the upgraded T2K near detector (ND280) shows good improvement in overall timing resolution, demonstrating the effectiveness in a real-world scenario and scalability.

calibration and fitting methods↗
DOE OSTI2023

Measurement of Electron-Neutrino Charged-Current Cross Sections on 127 I with the COHERENT NaI$ν$E Detector

Using an 185-kg NaI[Tl] array, COHERENT has measured the inclusive electron-neutrino chargedcurrent cross section on 127 I with pion decay-at-rest neutrinos produced by the Spallation Neutron Source at Oak Ridge National Laboratory. Iodine is one the heaviest targets for which low-energy (≤ 50 MeV) inelastic neutrino-nucleus processes have been measured, and this is the first measurement of its inclusive cross section. After a five-year detector exposure, COHERENT reports a flux-averaged cross section for electron neutrinos of ${9.2}_{–1.8}^{+2.1}$ × 10 –40 cm 2 . This corresponds to a value that is ~41% lower than predicted using the MARLEY event generator with a measured Gamow-Teller strength distribution. In addition, the observed visible spectrum from charged-current scattering on 127 I has been measured between 10 and 55 MeV, and the exclusive zero-neutron and one-or-more-neutron emission cross sections are measured to be ${5.2}_{–3.1}^{+3.4}$ × 10 –40 and ${2.2}_{—2.2}^{+3.5}$ × 10 –40 cm 2 , respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Tumor Microenvironment Targeting Nano–Bio Emulsion for Synergistic Combinational X-Ray PDT with Oncolytic Bacteria Therapy

Various cancer therapies have been developed, but tumor recurrence with incomplete tumor killing and remaining tumor cells/tissues is frequent in monotherapies. Herein, a nano–bio therapeutic emulsion formulated with multifunctional nanoscintillators and anaerobic Clostridium novyi-NT spores for synergistic image-guided combinational cancer therapy is reported. MRI visible nanoscintillators (NSs) are synthesized with a NaGdF 4 :Tb,Ce@NaGdF 4 core/shell structure for an image-guided X-ray photodynamic therapy (PDT) of the normoxic peripheral tumor. An anaerobic oncolytic bacterium (C. novyi-NT) therapy is combined to treat the hypoxic central tumor tissues. Photosensitizer-coated NSs (PS-NSs) and C. novyi-NT spores are emulsified with clinically available ethiodized oil (Lipiodol) to be the nano–bio therapeutic emulsion and injected into the tumor with computed tomography image guidance. The distribution of nano–bio therapeutic emulsion, including PS-NSs and anaerobic C. novyi-NT spores in the tumor site, is confirmed by both X-ray and T1-weighted magnetic resonance imaging. Following the image-guided X-ray PDT and anaerobic C. novyi- NT combination treatment, apoptotic cell death in cancer tissues, including both peripheral and central tumor regions, is significantly higher than in the control groups. Finally, this combination therapy approach using a nano–bio therapeutic emulsion is expected to overcome the limitations of conventional cancer therapy, resulting in increased cancer-therapeutic efficacy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Statistical analysis of the performance and long-term stability of unquenched LSC standards ( 3 H, 14 C) used for radiochemical measurements

Multiple sets of toluene-based unquenched standards, procured over the last 3 decades, were analyzed to determine their stability over time. A statistical analysis was performed to provide insight into the variability for tSIE and counting efficiency measurements of 3 H and 14 C isotopes. Our data suggests that standards remain viable even 30 years after the manufacturer’s recommended expiration date. Overall, these standards have shown no statistically significant sign of performance degradation. We have proven through statistical analysis that these standards can provide comparable performance over time well past their manufactured expiration date.

LSC standards↗
DOE OSTI2023

Influence of irrigation approaches and spatial geolocation on tritium speciation, uptake and depuration

Pine needles and tree cores from a tritium (T) contaminated phytoremediation forest at the Savannah River Site (SRS in Aiken, SC) Mixed Waste Management Facility (MWMF) were measured for total T and T speciation and compared to other locations at the SRS and the surrounding area. Tree core ages ranged from 9 to 14 years old, covering over half of the ~20-year on-going remediation efforts, while pine needles represent more recent time periods of 1-to-2-year increments. Remedial irrigation efforts at the MWMF are found to directly influence the pine needle T concentrations. The T content in the MWMF samples is higher than non-irrigated needle samples from other locations around the SRS. Furthermore, the different forms of organic bound T are preferentially stored in tree core tissue, compared to pine needles where tritiated water dominates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Computational modeling and neutron imaging to understand interface shape and solute segregation during the vertical gradient freeze growth of BaBrCl:Eu

In this work we apply continuum models to analyze phase change, heat transfer, fluid flow, solute transport, and segregation in order to understand prior neutron imaging observations of the vertical gradient freeze growth of Eu-doped BaBrCl. The models provide a rigorous framework in which to understand the mechanisms that are responsible for the complicated evolution of interface shape and dopant distribution in the growth experiment. We explain how a transition in the solid/liquid interface shape from concave to convex is driven by changes in radial heat transfer caused by furnace design. We also provide a mechanistic explanation of how dynamic growth conditions and changes of the flow structure in the melt result in complicated segregation patterns in this system. A growth pause caused by controller lock-up is shown to result in a band of solute depletion in accordance with classical theory. However, changing flow patterns during growth result in a non-monotonic axial distribution of solute that cannot be explained by simple application of classical segregation models. We assert that the approach presented here, namely the use of rigorous models in conjunction advanced diagnostics, such as neutron imaging, provides an exciting path forward for process optimization and control, accelerating the incremental advances that have, in the past, typically relied on empiricism, experience, and intuition.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Analysis of chemical stress and the propensity for cracking during the vertical Bridgman growth of BaBrCl:Eu

Computational models are employed to analyze residual chemical stresses arising from compositional variations in europium-doped BaBrCl crystals grown by the vertical Bridgman method. We find that significant chemical stress is produced by radial segregation of Eu in this system. In particular, the distribution of normal stresses is set by the radial concentration gradient, whose changing sign produces surface states in tension or compression. Additionally, crack opening from surface flaws will be promoted or suppressed by tensile or compressive surface stresses, respectively. Thus, crystal growth processing strategies that change the radial dopant concentration gradients are posited to affect the propensity for cracking. For this system, surface stresses are changed from states of tension to compression when the growth rate is increased, thus improving the chances to avoid cracking—a strategy that defies classical wisdom that dictates slower growth to improve outcomes. Similar strategies affecting segregation may prove beneficial to tailor chemical stress fields to reduce cracking in other crystal growth systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Crystal growth, physical and optical properties of TlSr 2 Cl 5 and TlSr 2 Br 5

Small diameter (Ø 16 mm) TlSr 2 Cl 5 and TlSr 2 Br 5 crystals were grown by the Vertical Bridgman method. X-ray diffraction measurements show that both have the monoclinic crystal structure with space group P21/c. TlSr 2 Cl 5 and TlSr 2 Br 5 have a density of 4.14 g/cm 3 and 5.03 g/cm 3 , respectively. The effective Z of TlSr 2 Cl 5 and TlSr 2 Br 5 is 63.7 and 58.6, respectively. Radioluminescence spectra of TlSr 2 Cl 5 and TlSr 2 Br 5 feature a broad emission band peaking at 440 and 445 nm, respectively. As a result the light yield of TlSr 2 Cl 5 and TlSr 2 Br 5 was estimated to be 17,000 and 45,000 ph/MeV, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Quantitative and three-dimensional assessment of holdup material

Nuclear material deposited in equipment, transfer lines, and ventilation systems of a processing facility is usually referred to as holdup. Operators need to know the location and amount of holdup in their facility for radiation safety and material accountability. In this work, we propose to use an array of detectors co-axial to the inspected pipe to measure the holdup material. This method is implementable into an automated system capable of crawling on surfaces and pipes of various curvatures, which would enable faster, easier, and more accurate holdup safeguards measurements. We first demonstrated that the current holdup assay procedure could lead to a non-negligible bias in the estimate of special nuclear material mass, due to the simplified assumption of deposited geometry introduced by the Generalized Geometry Holdup (GGH) model. The new approach consists of imaging the inner holdup material by characterizing the detector array’s response and unfolding it from the measured light output. Our experimental proof of principle consists of three NaI(Tl) detectors surrounding an aluminum pipe containing two cesium-137 ( 137 Cs) sources. We derived the source distribution inside the pipe by first calculating the detector response matrix using a method adaptive to the surface geometry of the object containing the measured holdup material. Creating a matrix of the detector array’s measured counts, we then proceed to solve an inverse problem, resulting in an accurately located source position and activity distribution within the response matrix’s spatial resolution. Furthermore, we then developed a simulated model of the envisioned experimental setup, which accurately described both the activity and position of the source in 2D. Finally, we extended our model onto a discretized three-dimensional model of the system, encompassing 36 detectors. The model was simulated to measure the source distribution and activity of multiple sources in pipes of varied geometries, which could then be conveniently translated to a real-time holdup measurement protocol. For the 3D simulation of four different source geometries, the model accurately localized the source position in 3D, while the activity retained a maximum relative error of ±5.32%.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗