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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Functional CeO x nanoglues for robust atomically dispersed catalysts

Single-atom catalysts make exceptionally efficient use of expensive noble metals and can bring out unique properties. However, applications are usually compromised by limited catalyst stability, which is due to sintering. Although sintering can be suppressed by anchoring the metal atoms to oxide supports, strong metal–oxygen interactions often leave too few metal sites available for reactant binding and catalysis, and when exposed to reducing conditions at sufficiently high temperatures, even oxide-anchored single-atom catalysts eventually sinter. Here we show that the beneficial effects of anchoring can be enhanced by confining the atomically dispersed metal atoms on oxide nanoclusters or ‘nanoglues’, which themselves are dispersed and immobilized on a robust, high-surface-area support. We demonstrate the strategy by grafting isolated and defective CeO x nanoglue islands onto high-surface-area SiO 2 ; the nanoglue islands then each host on average one Pt atom. Further, we find that the Pt atoms remain dispersed under both oxidizing and reducing environments at high temperatures, and that the activated catalyst exhibits markedly increased activity for CO oxidation. We attribute the improved stability under reducing conditions to the support structure and the much stronger affinity of Pt atoms for CeO x than for SiO 2 , which ensures the Pt atoms can move but remain confined to their respective nanoglue islands. The strategy of using functional nanoglues to confine atomically dispersed metals and simultaneously enhance their reactivity is general, and we anticipate that it will take single-atom catalysts a step closer to practical applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Numerical analysis of gas exhaust in Wendelstein 7-X using the direct simulation Monte Carlo method

The present work is focused on a 3D numerical assessment of the Wendelstein 7-X (W7-X) particle exhaust. For all the numerical simulations the direct simulation Monte Carlo solver of the DIVGAS workflow, has been employed. The complex 3D geometry of the sub-divertor region includes the pumping gap panel, supporting structures, cooling pipes as well as the cryo-vacuum pump. All the considered flow simulations correspond to the Standard magnetic configuration of W7-X. The main conclusions, which can be extracted from the present numerical analysis could be summarized as follows; The coupling between EMC3-EIRENE and DIVGAS, which considers the fact that the incoming neutral particle flux at the sub-divertor is based on realistic plasma background, has been demonstrated. Three plasma scenarios have been considered, for which is clearly seen that by increasing the heating power, the neutral pressure as well as the resulting pumping efficiency is increased. The obtained numerical results of the neutral pressure in the sub-divertor lie within a more general scan matrix, which assumes a wider range of incoming particle flux, namely 10 19 –10 24 (s −1 ). It has been observed that, the sub-divertor neutral pressure is proportional to the incoming neutral particle flux, with the effective pumping speed to be a constant of proportionality. The influence of switching off the cryo-vacuum pump on the sub-divertor pressure is rather modest and a weak increase of the neutral pressure in the sub-divertor is expected. Correlations of the sub-divertor pressure with the total incoming particle flux as well as the individual pumped flux at each of the AEH and AEP sections have been deduced. Moreover, it has been demonstrated that the influence of the incoming neutral particle flux on the albedo coefficient at the AEH and AEP pumping gaps is rather weak. All the above numerical findings will actively support the optimization of the W7-X particle exhaust, in view of future experimental campaigns.

DSMC method↗
DOE OSTI2020

Groundwater Monitoring Report, U.S. Department of Energy Y-12 National Security Complex, Oak Ridge, Tennessee

This report contains the groundwater and surface water monitoring data obtained during calendar year (CY) 2019 at the U.S. Department of Energy (DOE) Y-12 National Security Complex (Y-12) on the DOE Oak Ridge Reservation (ORR) in Oak Ridge, Tennessee. The monitoring data were obtained from wells, springs, and surface water sampling locations in three hydrogeologic regimes at Y-12. The Bear Creek Hydrogeologic Regime (Bear Creek Regime) encompasses a section of Bear Creek Valley (BCV) between the west end of Y-12 and the west end of the Bear Creek Watershed (directions are in reference to the Y-12 grid system, shown as Plant North. The Upper East Fork Poplar Creek Hydrogeologic Regime (East Fork Regime) encompasses the Y-12 industrial facilities and support structures in BCV. The Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime) encompasses a section of Chestnut Ridge directly south of Y-12. Background information in Section 2 of this report outlines the hydrogeologic framework for groundwater and surface water quality monitoring at Y-12 and includes an overview of the groundwater contamination in each hydrogeologic regime. Section 3 provides details regarding the groundwater and surface water sampling and analysis activities implemented under the Y-12 GWPP, including sampling locations and frequency, sample collection and handling, field measurements and laboratory analytes, quality assurance (QA)/quality control (QC) sampling, data management, and data quality assessment (DQA). However, the equivalent QA/QC or DQA information for the groundwater and surface water data associated with the monitoring programs implemented by UCOR are not included in this report and instead are deferred to referenced programmatic plans and reports issued by OREM and UCOR. Section 4 of this report presents a summary evaluation of the CY 2019 monitoring data with regard to the respective objectives of surveillance monitoring and exit pathway/perimeter monitoring. The evaluation is based primarily on the analytical results for the following principal groundwater contaminants at Y-12: nitrate, uranium, gross alpha activity, gross beta activity, and volatile organic compounds (VOCs). Section 5 summarizes the most significant findings with respect to the principal contaminants along with recommendations for any proposed changes to the ongoing groundwater and surface water quality monitoring performed under the Y-12 GWPP. Technical reports and plans cited in the narrative sections of the report are listed in Section 6. Narrative sections of this report reference several appendices. Figures (maps and diagrams) and data tables (excluding data summary tables incorporated in the narrative sections) are in Appendix A and Appendix B, respectively. Appendix C contains construction details for each well sampled during CY 2019 by either the Y-12 GWPP or UCOR, along with schematic diagrams for wells equipped with Westbay™ multiport sampling equipment or Barcad® pump systems. Appendix D supports the background summary discussion in Section 2 and provides more detailed information about the hydrogeologic framework for groundwater and surface water monitoring at Y-12, including the primary sources of groundwater contamination in each hydrogeologic regime. Results for all field measurements and laboratory analyses obtained by the Y-12 GWPP and UCOR are presented in Appendix E, which also includes the sample numbers for the QA/QC samples associated with groundwater and surface water monitoring performed by the Y-12 GWPP.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Process-dependent anisotropic thermal conductivity of laser powder bed fusion AlSi10Mg: impact of microstructure and aluminum-silicon interfaces

Purpose AlSi10Mg alloy is commonly used in laser powder bed fusion due to its printability, relatively high thermal conductivity, low density and good mechanical properties. However, the thermal conductivity of as-built materials as a function of processing (energy density, laser power, laser scanning speed, support structure) and build orientation, are not well explored in the literature. This study aims to elucidate the relationship between processing, microstructure, and thermal conductivity. Design/methodology/approach The thermal conductivity of laser powder bed fusion (L-PBF) AlSi10Mg samples are investigated by the flash diffusivity and frequency domain thermoreflectance (FDTR) techniques. Thermal conductivities are linked to the microstructure of L-PBF AlSi10Mg, which changes with processing conditions. The through-plane exceeded the in-plane thermal conductivity for all energy densities. A co-located thermal conductivity map by frequency domain thermoreflectance (FDTR) and crystallographic grain orientation map by electron backscattered diffraction (EBSD) was used to investigate the effect of microstructure on thermal conductivity. Findings The highest through-plane thermal conductivity (136 ± 2 W/m-K) was achieved at 59 J/mm 3 and exceeded the values reported previously. The in-plane thermal conductivity peaked at 117 ± 2 W/m-K at 50 J/mm 3 . The trend of thermal conductivity reducing with energy density at similar porosity was primarily due to the reduced grain size producing more Al-Si interfaces that pose thermal resistance. At these interfaces, thermal energy must convert from electrons in the aluminum to phonons in the silicon. The co-located thermal conductivity and crystallographic grain orientation maps confirmed that larger colonies of columnar grains have higher thermal conductivity compared to smaller columnar grains. Practical implications The thermal properties of AlSi10Mg are crucial to heat transfer applications including additively manufactured heatsinks, cold plates, vapor chambers, heat pipes, enclosures and heat exchangers. Additionally, thermal-based nondestructive testing methods require these properties for applications such as defect detection and simulation of L-PBF processes. Industrial standards for L-PBF processes and components can use the data for thermal applications. Originality/value To the best of the authors’ knowledge, this paper is the first to make coupled thermal conductivity maps that were matched to microstructure for L-PBF AlSi10Mg aluminum alloy. This was achieved by a unique in-house thermal conductivity mapping setup and relating the data to local SEM EBSD maps. This provides the first conclusive proof that larger grain sizes can achieve higher thermal conductivity for this processing method and material system. This study also shows that control of the solidification can result in higher thermal conductivity. It was also the first to find that the build substrate (with or without support) has a large effect on thermal conductivity.

Engineering↗
DOE OSTI2025

Ternary Potassium‐Bismuth‐Telluride Intermetallic Support Promotes Electrochemical Stability in Potassium Metal Anodes

We employed accumulative roll bonding to fabricate self‐standing metallurgical composite of in situ formed alkaline potassium‐bismuth‐telluride intermetallic K 2 (Bi 2/6 Te 3/6 Vac 1/6 ) embedded in potassium metal. This newly discovered thermodynamically stable potassiophilic crystal, termed “KBT”, is fcc antifluorite with K 2 Te archetype. Symmetric cells achieve 880 h of cycling at 0.5 mA cm −2 and 0.5 mAh cm −2 . Potassium metal battery (KMB) with Prussian blue (PB) cathode in carbonate electrolyte retains 80% capacity after 200 cycles at 1C. In ether‐based electrolyte with organic cathode, it achieves 80% retention after 900 cycles at 2C. Combined synchrotron X‐ray nano‐tomography, cryogenic‐focused ion beam microscopy (Cryo‐FIB) and sputter‐down X‐ray photoelectron spectroscopy (XPS) demonstrate uniform electrodeposits, versus baseline of potassium filaments intermixed with pores and coarse SEI. Binary K 3 Bi‐K and K 2 Te‐K intermetallic supports also provide improved electrochemical performance, albeit to lesser extent. Multiscale simulation provides insight into role of support structure in adatom energetics, film nucleation, early‐stage SEI morphology and interfacial stability.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Polymers in direct air capture: a mini review

The urgent need to mitigate climate change has intensified interest in direct air capture (DAC) technology, which targets extracting carbon dioxide (CO2) directly from the atmosphere. Among the various sorbents used in DAC, polymers have emerged as a promising solution, either as active sorbents or as structural supports for active DAC materials, due to their customizable properties, scalability and low cost. This mini-review investigates the latest trends in polymer-based materials for DAC and identifies critical research gaps, such as the need for thorough lifecycle assessments and in-depth studies on the degradation of polymeric materials. It also outlines future directions, emphasizing the importance of developing cost-effective, scalable and durable polymers that can perform efficiently across diverse climatic conditions, including the unique challenges presented by cold weather regions abundant in renewable energy. This mini-review aims to inform ongoing efforts in the design and utilization of polymeric sorbents, providing insights that could guide the development of economically viable and environmentally sustainable DAC technologies.

climate change↗
DOE OSTI2022

Super‐Hydrophilic Microporous Ni(OH) x /Ni 3 S 2 Heterostructure Electrocatalyst for Large‐Current‐Density Hydrogen Evolution

Abstract Exploiting active and stable non‐precious metal electrocatalysts for alkaline hydrogen evolution reaction (HER) at large current density plays a key role in realizing large‐scale industrial hydrogen generation. Herein, a self‐supported microporous Ni(OH) x /Ni 3 S 2 heterostructure electrocatalyst on nickel foam (Ni(OH) x /Ni 3 S 2 /NF) that possesses super‐hydrophilic property through an electrochemical process is rationally designed and fabricated. Benefiting from the super‐hydrophilic property, microporous feature, and self‐supported structure, the electrocatalyst exhibits an exceptional HER performance at large current density in 1.0 M KOH, only requiring low overpotential of 126, 193, and 238 mV to reach a current density of 100, 500, and 1000 mA cm −2 , respectively, and displaying a long‐term durability up to 1000 h, which is among the state‐of‐the‐art non‐precious metal electrocatalysts. Combining hard X‐rays absorption spectroscopy and first‐principles calculation, it also reveals that the strong electronic coupling at the interface of the heterostructure facilitates the dissociation of H 2 O molecular, accelerating the HER kinetics in alkaline electrolyte. This work sheds a light on developing advanced non‐precious metal electrocatalysts for industrial hydrogen production by means of constructing a super‐hydrophilic microporous heterostructure.

Chemistry↗
DOE OSTI2021

Unlocking large compressive strains in thin active elastocaloric layers

Elastocaloric cooling attracts broad interest and rapidly growing attention due to its potential for high efficiency and low environmental impact. While it is common knowledge that triggering reversible entropy and temperature changes with stress applied in compression prevents rapid failures of materials, realizing this regime in elastocaloric systems is highly challenging because nearly all geometries suited for efficient heat transfer are prone to buckling even under modest loads. This work describes a concept of a novel composite, where an active NiTi layer is embedded into a polymer support structure such that the elastocaloric material is entirely in compression when the assembly is subjected to bending. The active layer achieves 8.1 K temperature change at 2.5% compressive strain without buckling. After 10,000 cycles at 2% compressive strain, the composite maintains mechanical integrity without degradation of the elastocaloric effect. The results demonstrate that NiTi and, potentially, other elastocalorically active materials in geometries previously thought impossible can be successfully implemented in regenerative cooling systems operating in compression.

42 ENGINEERING↗
DOE OSTI2022

Neutron scattering maps the higher-order assembly of NADPH-dependent assimilatory sulfite reductase

Precursor molecules for biomass incorporation must be imported into cells and made available to the molecular machines that build the cell. Sulfur-containing macromolecules require that sulfur be in its S2- oxidation state before assimilation into amino acids, cofactors, and vitamins that are essential to organisms throughout the biosphere. In α-proteobacteria, NADPH-dependent assimilatory sulfite reductase (SiR) performs the final six-electron reduction of sulfur. SiR is a dodecameric oxidoreductase composed of an octameric flavoprotein reductase (SiRFP) and four hemoprotein metalloenzyme oxidases (SiRHPs). SiR performs the electron transfer reduction reaction to produce sulfide from sulfite through coordinated domain movements and subunit interactions without release of partially reduced intermediates. Efforts to understand the electron transfer mechanism responsible for SiR’s efficiency are confounded by structural heterogeneity arising from intrinsically disordered regions throughout its complex, including the flexible linker joining SiRFP’s flavin-binding domains. As a result, high-resolution structures of SiR dodecamer and its subcomplexes are unknown, leaving a gap in the fundamental understanding of how SiR performs this uniquely large-volume electron transfer reaction. In this work, we use deuterium labeling, in vitro reconstitution, analytical ultracentrifugation (AUC), small-angle neutron scattering (SANS), and neutron contrast variation (NCV) to observe the relative subunit positions within SiR’s higher-order assembly. AUC and SANS reveal SiR to be a flexible dodecamer and confirm the mismatched SiRFP and SiRHP subunit stoichiometry. NCV shows that the complex is asymmetric, with SiRHP on the periphery of the complex and the centers of mass between SiRFP and SiRHP components over 100 Å apart. SiRFP undergoes compaction upon assembly into SiR’s dodecamer and SiRHP adopts multiple positions in the complex. The resulting map of SiR’s higher-order structure supports a cis/trans mechanism for electron transfer between domains of reductase subunits as well as between tightly bound or transiently interacting reductase and oxidase subunits.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Durability of PGM catalyst MEAs of polymer electrolyte membrane fuel cells for heavy-duty vehicles

Polymer electrolyte membrane fuel cells (PEMFCs) are promising power sources for heavy-duty vehicles (HDVs) owing to cleanliness and efficiency. However, the degradation of membrane electrode assemblies (MEAs) under HDV conditions remains a huge challenge. Here, this work investigated MEA durability under HDV conditions using a US Department of Energy standard accelerated stress test for 180,000 cycles (equivalent to 1 million miles of HDV operation). Effects of catalyst Pt content on MEA durability were examined using homemade 30% Pt/C (H-Pt/C) and commercial 46% Pt/C (C-Pt/C) catalysts. Both MEAs experienced H 2 /air and H 2 /O 2 performance loss over cycles. Analysis with scanning transmission electron microscopy, X-ray diffraction, inductively coupled plasma mass spectrometry, and mercury intrusion porosimetry revealed severe degradation of Pt nanoparticles (NPs), support structures, and the catalyst layer. Two degradation stages for NPs were proposed: Ostwald ripening dominated the initial 60,000 cycles, followed by combined Ostwald ripening and particle migration. Measurements with ion chromatography, high-frequency resistance, and oxygen-diffusion resistance revealed degradation of membrane and ionomer, respectively.

25 ENERGY STORAGE↗
DOE OSTI2022

Design optimization of an additively manufactured prototype recuperator for supercritical CO 2 power cycles

Supercritical CO 2 (sCO 2 ) power cycles are being developed due to their potential for high efficiency and reduced capital cost. It is necessary that these recuperators operate at high pressures and temperatures, up to 30 MPa and 900 K, with effectiveness values > 95% and pressure drops <1% to achieve high cycle efficiencies. Moreover, it is also necessary to have reasonable cost recuperators to control the capital costs of the sCO 2 power cycles. In this study, a Plate Pin-Fin (PPF) heat exchanger has been proposed as an sCO 2 recuperator. This preliminary recuperator design leverages capabilities enabled by additive manufacturing. Although the PPF design has characteristics similar to those of a plate heat exchanger, small diameter and relatively long fins are used to increase surface area, enhance heat transfer, and provide structural support for the partition plates that separate the fluid streams. Existing correlations for heat transfer and pressure drop were adapted for the PPF heat exchanger. These correlations were implemented in a 1D analytical model and used for the optimization of a 5-kW th high temperature recuperator for an indirect sCO 2 cycle by varying the design parameters to minimize the quantity of material required. A 3D conjugate heat transfer numerical simulations were conducted to validate the heat transfer and pressure loss correlations. A steepest descent method was used to minimize heat exchanger mass for a 5-kW prototype recuperator subject to a maximum specified pressure drop. Additionally, the design analysis indicated that an optimum PPF recuperator would be attained for the minimum allowable pin transverse spacing, minimum pin width, minimum pin height and near maximum cell aspect ratio. Moreover, at a low material requirement of 0.216 kg/kW and a pressure drop, which is almost five times lower than the allowable pressure drop design target, the optimized PPF heat exchanger has the high potential to be an alternative to a printed circuit heat exchanger, which is a conservative design basis for the current state-of-the-art sCO 2 recuperators.

42 ENGINEERING↗
DOE OSTI2021

Serpent neutronics model of Wendelstein 7-X for 14.1 MeV neutrons

In this work, a Serpent 2 neutronics model of the Wendelstein 7-X (W7-X) stellarator is prepared, and an response function for the Scintillating-Fibre neutron detector (SciFi) is calculated using the model. The neutronics model includes the simplified geometry for the key components of the stellarator itself as well as the torus hall. The objective of the model is to assess the 14.1 MeV neutron flux from deuteron-triton fusions in W7-X, where the neutrons are modelled only until they have slowed down to 1 MeV energy. The key messages of this article are: demonstration of unstructured mesh geometry usage for stellarators, W7-X in particular; technical documentation of the model and first insights in fast neutron behaviour in W7-X, especially related to the SciFi: the model indicates that the superconducting coils are the strongest scatterers and block neutrons from large parts of the plasma. The back-scattering from e.g. massive steel support structures is found to be small. The SciFi will detect neutrons from an extended plasma volume in contrast to having an effective line-of-sight.

14 MeV↗
DOE OSTI2021

Determination of oxidation rates and volatile oxidation products for HTGR graphite matrix material exposed to steam atmospheres

High-temperature gas-cooled reactors (HTGRs) in operation use tristructural isotropic (TRISO) particles embedded in graphite and carbonized resin matrix to form the fuel element. This graphite matrix material serves as a supportive structural element, heat transfer medium, and neutron moderator. In HTGR designs, fuel compacts are exposed to helium coolant, which facilitates high outlet temperatures (750°C 2 O, 800°C 2 , and H 2 , are quantified in varied oxidant atmospheres using a coupled thermogravimetric analyzer and mass spectrometer. Furthermore, oxidation rates reported here for varied steam (H 2 O [g]) atmospheres are predominantly linear and comparable with literature values in the range of tested temperatures (800–1200°C). Changes in dominant matrix oxidation products from primarily CO to a mixture of CO, CO 2 , and H 2 were observed at higher temperatures (≥1000°C) and steam atmospheres (≥5 kPa pH 2 O). Kinetic data indicates that there was no shift in oxidation regime with chemical oxidation occurring at all temperatures and H2O (g) atmospheres tested. These data provide insight into the oxidation behavior of graphite matrix material and will inform future testing conditions, notably mixed atmospheric conditions, of HTGR fuel elements.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Compressible battery foams to prevent cascading thermal runaway in Li-ion pouch batteries

Lithium-ion battery packs require thermal management to achieve optimum life and safety. This is becoming crucial for battery packs composed of high-energy-density cells. Pouch cells themselves achieve highest packaging efficiency but require additional structural support and thermal management when grouped into modules, especially under abusive conditions such as thermal runaway. Novel foam battery pads have demonstrated to cushion volume changes of pouch cells and are reengineered in this study to mitigate cell-to-cell thermal runaway propagation. The compressible pads are made of polyurethane foams incorporating flame-retardant additives or coatings, including intumescent and fire wall materials. Here their performances were evaluated by conducting nail penetration tests on modules composed of pouch cells at 100% state of charge (SOC), with the foams placed in between the cells. Experimental results show cascading thermal runaway was considerably delayed by polyurethane foams incorporating flame-retardant additives or coatings. Complete prevention of cascading failure was achieved with dense polyurethane foams with multilayered coatings of both fire wall and intumescent materials.

25 ENERGY STORAGE↗
DOE OSTI2023

Investigation of thermal hydraulic behavior of the High Temperature Test Facility's lower plenum via large eddy simulation

A high-fidelity computational fluid dynamics (CFD) analysis was performed using the Large Eddy Simulation (LES) model for the lower plenum of the High–Temperature Test Facility (HTTF), a ¼ scale test facility of the modular high temperature gas-cooled reactor (MHTGR) managed by Oregon State University. In most next–generation nuclear reactors, thermal stress due to thermal striping is one of the risks to be curiously considered. This is also true for HTGRs, especially since the exhaust helium gas temperature is high. In order to evaluate these risks and performance, organizations in the United States led by the OECD NEA are conducting a thermal hydraulic code benchmark for HTGR, and the test facility used for this benchmark is HTTF. HTTF can perform experiments in both normal and accident situations and provide high-quality experimental data. However, it is difficult to provide sufficient data for benchmarking through experiments, and there is a problem with the reliability of CFD analysis results based on Reynolds–averaged Navier–Stokes to analyze thermal hydraulic behavior without verification. To solve this problem, high-fidelity 3-D CFD analysis was performed using the LES model for HTTF. It was also verified that the LES model can properly simulate this jet mixing phenomenon via a unit cell test that provides experimental information. As a result of CFD analysis, the lower the dependency of the sub-grid scale model, the closer to the actual analysis result. In the case of unit cell test CFD analysis and HTTF CFD analysis, the volume-averaged sub-grid scale model dependency was calculated to be 13.0% and 9.16%, respectively. As a result of HTTF analysis, quantitative data of the fluid inside the HTTF lower plenum was provided in this paper. As a result of qualitative analysis, the temperature was highest at the center of the lower plenum, while the temperature fluctuation was highest near the edge of the lower plenum wall. The power spectral density of temperature was analyzed via fast Fourier transform (FFT) for specific points on the center and side of the lower plenum. FFT results did not reveal specific frequency-dominant temperature fluctuations in the center part. It was confirmed that the temperature power spectral density (PSD) at the top increased from the center to the wake. The vortex was visualized using the well-known scalar Q-criterion, and as a result, the closer to the outlet duct, the greater the influence of the mainstream, so that the inflow jet vortex was dissipated and mixed at the top of the lower plenum. Additionally, FFT analysis was performed on the support structure near the corner of the lower plenum with large temperature fluctuations, and as a result, it was confirmed that the temperature fluctuation of the flow did not have a significant effect near the corner wall. In addition, the vortices generated from the lower plenum to the outlet duct were identified in this paper. It is considered that the quantitative and qualitative results presented in this paper will serve as reference data for the benchmark.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Novel X-ray scanning technique for in-situ alignment of photo-detectors in the MEGII calorimeter

Here, we describe and show results of a novel technique to measure with high precision the positions of photodetectors installed in the upgraded liquid xenon calorimeter of the MEG II experiment. The measurement was done by detecting the signal in individual photo-detectors as the front surface of the calorimeter was scanned in axial (Z) and azimuthal (Φ) directions with a precisely controlled, thin, collimated beam of X-rays obtained from a 57 CoX-ray source. The measurements were made when the calorimeter was cold and operational, under which conditions they could not otherwise be made. This technique is used to check for changes in the photodetector positions due to the effects of cooling and thermal cycling of the support structure and to provide a reference between the positions of the operational photodetectors and alignment markers on the cryostat exterior. The use of an essentially monochromatic X-ray source allowed ancillary measurements of photodetector properties, including pulse shape, relative gain, and variation in response over the photodetector surface. Measurement uncertainties below 0.6mm in Z and 0.7 mrad in Φ have been achieved, well within the requirements for the MEG II performance.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

The SHMS 11 GeV/c spectrometer in Hall C at Jefferson Lab

The Super High Momentum Spectrometer (SHMS) has been built for Hall C at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). With a momentum capability reaching 11 GeV/ c , the SHMS provides measurements of charged particles produced in electron-scattering experiments using the maximum available beam energy from the upgraded Jefferson Lab accelerator. The SHMS is an ion-optics magnetic spectrometer comprised of a series of new superconducting magnets which transport charged particles through an array of triggering, tracking, and particle-identification detectors that measure momentum, energy, angle and position in order to allow kinematic reconstruction of the events back to their origin at the scattering target. The detector system is protected from background radiation by a sophisticated shielding enclosure. The entire spectrometer is mounted on a rotating support structure which permits measurements to be taken with a large acceptance over laboratory scattering angles from 5.5° to 40°, thus allowing a wide range of low cross-section experiments to be conducted. Finally, these experiments complement and extend the previous Hall C research program to higher energies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Status and performance of the GlueX DIRC

In support of the future physics program at Ce+BAF, we propose a prototype positron target. The prototype target consists of a tungsten disk mounted on a water-cooled copper support structure to enhance heat removal. The primary goals of this work are to benchmark CFD simulations, ensure vacuum integrity at the 10^-6 Pa level, achieve stable target rotation up to 10 Hz, and implement efficient water-based cooling for sustained high-power operation. To manage the thermal load, the target is designed to rotate, allowing the deposited heat to spread over a larger region, and thereby reducing localized thermal stress while maintaining the maximum temperature below 1000 K. To experimentally evaluate the thermal performance and structural stability of the target, we plan to conduct high-power laser heating tests at Laser Lab 5, LERF Building, JLab. These tests will serve as a stepping-stone for the positron production target at CEBAF.

Stevens, J.R. [College of William and Mary, Willia↗