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DOE OSTI2024

Path-Integrated X-Ray Digital Image Correlation using Synthetic Reference Images

X-rays can provide images when an object is visibly obstructed, allowing for motion measurements via x-ray digital image correlation (DIC). However, x-ray images are path-integrated and contain data for all objects between the source and detector. If multiple objects are present in the x-ray path, conventional DIC algorithms may fail to correlate the x-ray images. A new DIC algorithm called path-integrated (PI)-DIC addresses this issue by reformulating the matching criterion for DIC to account for multiple, independently-moving objects. PI-DIC requires a set of reference x-ray images of each independent object. However, due to experimental constraints, such reference images might not be obtainable from the experiment. Here, this work focuses on the reliability of synthetically-generated reference images, in such cases. A simplified exemplar is used for demonstration purposes, consisting of two aluminum plates with tantalum x-ray DIC patterns undergoing independent rigid translations. Synthetic reference images based on the “as-designed” DIC patterns were generated. However, PI-DIC with the synthetic images suffered some biases due to manufacturing defects of the patterns. A systematic study of seven identified defect types found that an incorrect feature diameter was the most influential defect. Synthetic images were re-generated with the corrected feature diameter, and PI-DIC errors were improved by a factor of 3-4. Final biases ranged from 0.00-0.04 px, and standard uncertainties ranged from 0.06-0.11 px. In conclusion, PI-DIC accurately measured the independent displacement of two plates from a single series of path-integrated x-ray images using synthetically-generated reference images, and the methods and conclusions derived here can be extended to more generalized cases involving stereo PI-DIC for arbitrary specimen geometry and motion. This work thus extends the application space of x-ray imaging for full-field DIC measurements of multiple surfaces or objects in extreme environments where optical DIC is not possible.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Time-stepping DPG formulations for the heat equation

For a wide range of PDEs, the discontinuous Petrov–Galerkin (DPG) methodology of Demkowicz and Gopalakrishnan provides discrete stability starting from a coarse mesh and minimization of the residual in a user-controlled norm, among other appealing features. Research on DPG for transient problems has mainly focused on spacetime discretizations, which has theoretical advantages, but practical costs for computations and software implementations. The sole examination of time-stepping DPG formulations was performed by Führer, Heuer, and Gupta, who applied Rothe’s method to an ultraweak formulation of the heat equation to develop an implicit time-stepping scheme; their work emphasized theoretical results, including error estimates in time and space. Here, we follow Führer, Heuer, and Gupta in examining the heat equation; our focus is on numerical experiments, examining the stability and accuracy of several formulations, including primal as well as ultraweak, and explicit as well as implicit and Crank–Nicolson time-stepping schemes. We are additionally interested in communication-avoiding algorithms, and we therefore include a highly experimental formulation that places all the trace terms on the right-hand side of the equation.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2022

AGR-2 irradiated TRISO particle IPyC/SiC interface analysis using FIB-SEM tomography

In this work, the morphology in the interface region between the inner pyrolytic carbon layer (IPyC) and silicon carbide (SiC) layers in tristructural-isotropic (TRISO) particle fuel from the AGR-2 irradiation experiment were studied using focused ion beam-scanning electron microscopy tomography. This work quantitatively described the interface and corresponding relevant metrics to understand how the microstructural features at the IPyC/SiC interface may influence actinide and fission product interactions with the SiC layer. Particles were selected with varied 110m Ag retention rates, and their volumes were reconstructed and analyzed for distributions of pores, fission product/actinide features, SiC, and IPyC. It was found that porosity accommodates fission products in the interface and SiC layers. The largest fission product/actinide precipitates were found in the interface region. This was also where the largest number fraction of fission products/actinides was found, consistent with SEM showing fission product/actinide pileup along selected areas of the interface region.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Design of a high voltage delivery system for noble liquid time projection chambers

Noble liquid time projection chambers (TPCs) are a leading technology in the detection of ionizing radiation, particularly in applications such as accelerator neutrino physics, dark matter detection, and neutrinoless double beta decay. This work addresses the design considerations for implementing stable high voltage (HV) systems within large noble liquid TPCs, with a focus on the nEXO experiment. Utilizing insights from prior HV research and experimental investigations, we outline factors influencing HV stability and discuss design choices to improve stability and prevent electrical discharges. A novel HV delivery system concept is presented, tailored for the nEXO TPC, which incorporates these design considerations while also meeting the stringent radiopurity requirements of the nEXO neutrinoless double beta decay search. These design considerations and their specific implementation towards a HV delivery system offer guidance to future experiments applying high voltage in noble liquid environments.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

Laboratory plasma physics experiments using merging supersonic plasma jets

We describe a laboratory plasma physics experiment at Los Alamos National Laboratory that uses two merging supersonic plasma jets formed and launched by pulsed-power-driven railguns. The jets can be formed using any atomic species or mixture available in a compressed-gas bottle and have the following nominal initial parameters at the railgun nozzle exit: n e ≈ n i ~ 10¹⁶ cm⁻³, T e ≈ T i ≈ 1.4 eV, V jet ≈ 30–100 km/s, mean charge $\bar{Z}$ ≈ 1, sonic Mach number M s ≡ V jet /C s > 10, jet diameter = 5 cm, and jet length ≈ 20 cm. Experiments to date have focused on the study of merging-jet dynamics and the shocks that form as a result of the interaction, in both collisional and collisionless regimes with respect to the inter-jet classical ion mean free path, and with and without an applied magnetic field. However, many other studies are also possible, as discussed in this paper.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2016

Analysis tools for MesonEx at CLAS12

The JLAB upgrade will soon be completed and the new CLAS12 detector system will collect large volumes of data allowing detailed investigations of many aspects of hadron physics. The focus of the MesonEx experiment is on the production of mesonic states by low Q2 virtual photons, or quasi-real photons. Studying such mesonic states is a particularly challenging data analysis problem, requiring well understood detector systems, clean signal and background separation, handling of large volumes of data and crucially a close collaboration between experimentalists and theorists to ensure the most sophisticated theoretical methods are used to interrogate the data. Here we briefly outline some of the analysis and methods that are being used to prepare for the MesonEx experiment.

Glazier, Derek↗

DOE OSTI2022

Progress toward fusion energy breakeven and gain as measured against the Lawson criterion

The Lawson criterion is a key concept in the pursuit of fusion energy, relating the fuel density n, pulse duration τ or energy confinement time τE, and fuel temperature T to the energy gain Q of a fusion plasma. The purpose of this paper is to explain and review the Lawson criterion and to provide a compilation of achieved parameters for a broad range of historical and contemporary fusion experiments. Although this paper focuses on the Lawson criterion, it is only one of many equally important factors in assessing the progress and ultimate likelihood of any fusion concept becoming a commercially viable fusion-energy system. Only experimentally measured or inferred values of n, τ or τE, and T that have been published in the peer-reviewed literature are included in this paper, unless noted otherwise. For extracting these parameters, we discuss methodologies that are necessarily specific to different fusion approaches (including magnetic, inertial, and magneto-inertial fusion). This paper is intended to serve as a reference for fusion researchers and a tutorial for all others interested in fusion energy.

Wurzel, Samuel E. (ORCID:0000000260548161)↗

DOE OSTI2025

FAST Irradiations, Postirradiation Examinations, and Modeling of U-Mo for Light Water Reactor Applications

Many next generation light water reactor (LWR) concepts, such as mobile small modular reactors, are seeking to use smaller core dimensions than conventional reactor types. Smaller reactor cores require an increase in fissile material to maintain reactivity. For non-proliferation purposes, enrichment increases are limited to less than 20% (high assay low enriched uranium, [HALEU]) and so higher uranium density fuels than UO 2 must be considered. To this end, uranium-molybdenum alloys were tested using the Fission Accelerated Steady-state Test (FAST) approach. The experiment test matrix is focused on identifying the temperature transition between low swelling and high fission gas retention to break away swelling and low fission gas retention. This paper documents the results of irradiation tests and post-irradiation examinations (PIE) including neutron radiography, rodlet profilometry, fission gas collection analysis, and optical metallography. The results of these tests showed that unconstrained U-Mo fuels (solid, Na-bonded rodlets) have a swelling threshold between 400-450°C with minimal fission gas release below this point. Higher temperature solid fuel showed microstructural zoning with small pore networks while lower temperature solid fuels have a uniform microstructure with large pore networks. U-Annular Mo fuels where swelling had some self-constraint imposed upon it, were shown to have much reduced swelling compared to their solid counterparts as well as very low fission gas release for irradiation temperatures up to 500°C. These initial results show that the use of U-Mo in constrained fuel geometries could be used as a high uranium density HALEU fuel for LWRs.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2019

Scrape-off layer transport and filament characteristics in high-density tokamak regimes

A detailed cross-device investigation on the role of filamentary dynamics in high-density regimes has been performed within the EUROfusion framework, comparing the ASDEX Upgrade (AUG) and TCV tokamaks. Both devices run density ramp experiments at different levels of plasma current, keeping the toroidal field or q 95 constant in order to disentangle the role of the parallel connection length and the current. During the scan at a constant toroidal field, in both devices the scrape-off layer (SOL) profiles tend to develop a clear SOL density shoulder at a lower edge density whenever the current is reduced. Different current behaviour is substantially reconciled in terms of the edge density normalized to the Greenwald fraction. During the scan at constant q 95 AUG exhibits similar behaviour, whereas in TCV no upstream profile modification signature has been observed at lower current levels. The latter behaviour has been ascribed to the lack of target density rollover. In this work, the relation between the upstream density profile modification and detachment condition has been investigated. For both devices the relation between blob size and the SOL density e-folding length is found independent of the plasma current, with the observation of a clear increase in blob size and the edge density normalized to a Greenwald fraction. ASDEX Upgrade has also explored filamentary behaviour in the H-mode. The experiments in AUG have focused on the role of neutrals, performing discharges with and without cryogenic pumps, highlighting how high neutral pressure, not only in the divertor but also at the midplane, is needed in order to develop an H-mode SOL profile shoulder in AUG.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2023

Phase Space Reconstruction from Accelerator Beam Measurements Using Neural Networks and Differentiable Simulations

Characterizing the phase space distribution of particle beams in accelerators is a central part of accelerator understanding and performance optimization. However, conventional reconstruction-based techniques either use simplifying assumptions or require specialized diagnostics to infer high-dimensional (> $2D$) beam properties. In this Letter, we introduce a general-purpose algorithm that combines neural networks with differentiable particle tracking to efficiently reconstruct high-dimensional phase space distributions without using specialized beam diagnostics or beam manipulations. Furthermore, we demonstrate that our algorithm accurately reconstructs detailed 4D phase space distributions with corresponding confidence intervals in both simulation and experiment using a single focusing quadrupole and diagnostic screen. This technique allows for the measurement of multiple correlated phase spaces simultaneously, which will enable simplified 6D phase space distribution reconstructions in the future.

47 OTHER INSTRUMENTATION↗

DOE OSTI2018

Operational Experience with the MICE Spectrometer Solenoid System

The Muon Ionization Cooling Experiment located at Rutherford Appleton Laboratory in England utilizes a supercon-ducting solenoid system for the muon cooling channel that also holds particle tracking detectors and muon absorbers inside their bores. The solenoid system installation was completed in summer of 2015 and after commissioning the system it has been running successfully. As a result, this paper summarizes the commissioning results and operational experience with the magnets focusing on the per-formance of the two Spectrometer Solenoids built by the US.

43 PARTICLE ACCELERATORS↗

DOE OSTI2018

As-built new Mayall telescope top end for the DESI project

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2018

Fabrication of the DESI corrector lenses

The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 square degrees will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. We describe the DESI corrector optics, a series of six fused silica and borosilicate lenses. The lens diameters range from 0.8 to 1.1 meters, and their weights 84 to 237 kg. Most lens surfaces are spherical, and two are challenging 10 th -order polynomial aspheres. The lenses have been successfully polished and treated with an antireflection coating at multiple subcontractors, and are now being integrated into the DESI corrector barrel assembly at University College London. We describe the final performance of the lenses in terms of their various parameters, including surface figure, homogeneity, and others, and compare their final performance against the demanding DESI corrector requirements. Also we describe the reoptimization of the lens spacing in their corrector barrel after their final measurements are known. Finally we assess the performance of the corrector as a whole, compared to early budgeted estimates.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2018

Overview of the Dark Energy Spectroscopic Instrument

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Testing the 10 spectrograph units for DESI: approach and results

The recently commissioned Dark Energy Spectroscopic Instrument (DESI) will measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 sqdeg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope delivers light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. A consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP and CPPM) together with LPNHE (CNRS, IN2P3, Sorbonne Université and Université de Paris) and the WINLIGHT Systems company based in Pertuis (France), were in charge of integrating and validating the performance requirements of the ten full spectrographs, equipped with their cryostats, shutters and other mechanisms. We present a summary of our activity which allowed an efficient validation of the systems in a short-time schedule. We detail the main results. We emphasize the benefits of our approach and also its limitations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2022

Putting multipoint kinetics to the test: preliminary analysis of the MUSE-4 experiment with APOLLO3

Modeling neutron kinetics is a challenging task and over the years, several approaches have been developed offering different tradeoffs between precision and cost. Probably the most popular one is point kinetics (PK), which, despite being very cheap, provides good results for many applications. One of the limitations of PK is that it is not able to model effects that happen before the prompt jump time scale. In practice, applications, where those time scales are interesting, are rare and those for which experimental data are available are even rarer. One of those cases is the MUSE-4 experiment for which the focus is on the very fast behavior and where we have no thermal feedback. As we have shown in a recent paper, a simple extension of PK, known as multipoint kinetics (MPK), can overcome this limitation. In this paper, which is intended as a preliminary study, we show how a simple MPK model can qualitatively reproduce the fast behavior that we cannot model with PK. Moreover, we will show how to exploit its low cost and compact form to model also slow effects as the precursors built up, behaviours that are not affordable to model with more expensive techniques, such as kinetic Monte Carlo simulations. For the periodic pulse transients with no feedbacks we will also provide an analytical solution in closed form. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2015

Efficient modeling of Bragg coherent x-ray nanobeam diffraction

X-ray Bragg diffraction experiments that utilize tightly focused coherent beams produce complicated Bragg diffraction patterns that depend on scattering geometry, characteristics of the sample, and properties of the x-ray focusing optic. In this paper, we use a Fourier-transform-based method of modeling the 2D intensity distribution of a Bragg peak and apply it to the case of thin films illuminated with a Fresnel zone plate in three different Bragg scattering geometries. Finally, the calculations agree well with experimental coherent diffraction patterns, demonstrating that nanodiffraction patterns can be modeled at nonsymmetric Bragg conditions with this approach—a capability critical for advancing nanofocused x-ray diffraction microscopy.

36 MATERIALS SCIENCE↗

DOE OSTI2017

From lapis lazuli to ultramarine blue: investigating Cennino Cennini’s recipe using sulfur K-edge XANES

As one of the most desired and expensive artists’ materials throughout history, there has long been interest in studying natural lapis lazuli. The traditional method of extracting the blue component, lazurite, from lapis lazuli, as outlined in Cennini’s Il Libro dell’Arte , involves a lengthy purification process: (1) finely grind the rock; (2) mix with pine rosin, gum mastic, and beeswax; (3) massage in water to collect the lazurite. Repeating the process produces several grades of the pigment, typically referred to as ultramarine blue. Here, we investigate the sulfur environment within the aluminosilicate framework of lazurite during its extraction from lapis lazuli. The sulfur XANES fingerprint from samples taken at the different stages in Cennini’s extraction method were examined. All spectra contain a strong absorption peak at 2483 eV, attributable to sulfate present in the lazurite structure. However, intensity variations appear in the broad envelope of peaks between 2470 and 2475 eV and the pre-peak at 2469.1 eV, indicating a variation in the content of trisulfur (S 3 –˙ ) radicals. By studying the effect of each step of Cennini’s process, this study elucidates the changes occurring during the extraction and the variability within different grades of the precious coloring material. The increasing application of XANES to the study of artist’s materials and works of art motivated extending the research to assess the possibility of X-ray induced damage. Direct comparison of micro-focused and unfocused beam experiments suggests an increase of the S 3 –˙ radicals with prolonged exposure. Furthermore, analysis indicates that induced damage follows first-order kinetics, providing a first assessment on the acceptable amount of radiation exposure to define the optimal acquisition parameters to allow safe analyses of lapis lazuli and ultramarine pigments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗