Results for “ARCS” — Page 14

DOE OSTI2023

Detecting low-mass perturbers in cluster lenses using curved arc bases

ABSTRACT Strong gravitationally lensed arcs produced by galaxy clusters have been observationally detected for several decades now. These strong lensing constraints provided high-fidelity mass models for cluster lenses that include substructure down to $10^{9{-}10}\, \mathrm{M}_\odot$. Optimizing lens models, where the cluster mass distribution is modelled by a smooth component and subhaloes associated with the locations of individual cluster galaxies, has enabled deriving the subhalo mass function, providing important constraints on the nature and granularity of dark matter. In this work, we explore and present a novel method to detect and measure individual perturbers (subhaloes, line-of-sight haloes, and wandering supermassive black holes) by exploiting their proximity to highly distorted lensed arcs in galaxy clusters, and by modelling the local lensing distortions with curved arc bases. This method offers the possibility of detecting individual low-mass perturber subhaloes in clusters and haloes along the line of sight down to a mass resolution of $10^8\, \mathrm{M}_\odot$. We quantify our sensitivity to low-mass perturbers ($M\sim 10^{7{-}9}\, \mathrm{M}_\odot$) in clusters (M ∼ 1014–15 M⊙), by creating realistic mock data. Using three lensed images of a background galaxy in the cluster SMACS J0723, taken by JWST, we study the retrieval of the properties of potential perturbers with masses $M=10^{7{-}9}\, \mathrm{M}_\odot$. From the derived posterior probability distributions for the perturber, we constrain its concentration, redshift, and ellipticity. By allowing us to probe lower mass substructures, the use of curved arc bases can lead to powerful constraints on the nature of dark matter as discrimination between dark matter models appears on smaller scales.

Astronomy & Astrophysics↗

DOE OSTI2022

Rare-earth monopnictides: Family of antiferromagnets hosting magnetic Fermi arcs

We report since the discovery of topological insulators a great deal of research effort has been devoted to magnetic topological materials, in which nontrivial spin properties can be controlled by magnetic fields, culminating in a wealth of fundamental phenomena and possible applications. The main focus was on ferromagnetic materials that can host Weyl fermions and therefore spin-textured Fermi arcs. The recent discovery of Fermi arcs and new magnetic band splitting in the antiferromagnet (AFM) NdBi has opened up new avenues for exploration. Here we show that these uncharted effects are not restricted to this specific compound, but also emerge in CeBi and NdSb when they undergo paramagnetic to AFM transition. Our data show that the Fermi arcs in NdSb have twofold symmetry, leading to strong anisotropy that may enhance effects of spin textures on transport properties. Our findings thus demonstrate that the RBi and RSb series are materials that host magnetic Fermi arcs and may be a potential platform for modern spintronics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2022

Optimizing Multi-Robot Placements for Wire Arc Additive Manufacturing

Wire arc additive manufacturing is a metal additive manufacturing process in which the material is deposited using arc welding technology. It is gaining popularity due to high material deposition rates and faster build time. It is en-abled using robotic manipulators and can build relatively large-scale parts faster when compared with other metal additive manufacturing processes. However, the size of the large-scale parts is limited by the size of the industrial manipulator being used for the process. This limitation is overcome by using a fixed configuration multi-robot cell in which manipulators work cooperatively to build large-scale parts quickly. A fixed multi-robot cell with closely spaced industrial manipulators has high flexibility, but it restricts the part size that can be built. If the manipulators are spread out, the cell loses its flexibility but can build relatively larger parts. This issue can be avoided by using larger size manipulators, which are expensive, or by moving the modest size manipulators based on the part geometries. This paper presents a novel algorithm to generate multi-robot placements for different part geometries to be built using wire arc additive manufacturing. Furthermore, the algorithm hierarchically optimizes the build time and the inverse kinematics consistency in robot paths to improve the process efficiency and part quality. We compare the results with fixed multi-robot cells and provide insights to users to make an informed decision on whether to use a fixed or a flexible multi-robot cell for wire arc additive manufacturing.

Bhatt, Prahar↗

DOE OSTI2025

ARCS: Agentic Retrieval-Augmented Code Synthesis with Iterative Refinement

Agentic Retrieval-Augmented Code Synthesis with Iterative RefinementIn supercomputing, efficient and optimized code generation is essential to leverage high-performance systems effectively. We have developed Agentic Retrieval-Augmented Code Synthesis (ARCS), an advanced framework for accurate, robust, and efficient code generation, completion, and translation. ARCS integrates Retrieval-Augmented Generation (RAG) with Chain-of-Thought (CoT) reasoning to systematically break down and iteratively refine complex programming tasks. An agent-based RAG mechanism retrieves relevant code snippets, while real-time execution feedback drives the synthesis of candidate solutions. This process is formalized as a state-action search tree optimization, balancing code correctness with editing efficiency. Evaluations on the Geeks4Geeks and HumanEval benchmarks demonstrate that ARCS significantly outperforms traditional prompting methods in translation and generation quality. By enabling scalable and precise code synthesis, ARCS offers transformative potential for automating and optimizing code development in supercomputing applications, enhancing computational resource utilization

Bhattarai, Manish [Los Alamos National Labs]↗

DOE OSTI2025

Optimization of Scrap Melting Using an Electric Arc in Steel Manufacturing

Steel industry is crucial to the national economy and security. Around 67% of crude steel in the U.S is produced in electric arc furnaces (EAF), which is energy intensive. Around 140 EAFs operate in the U.S., consuming about 8.6x10 7 MMBtu/year of electricity. One of major challenges for EAFs includes maximizing the efficiency of the electrical energy provided in the form of electric arcs to melt various scrap mixes. To address this issue, a computational fluid dynamics (CFD) methodology is chosen to analyze scrap melting using the electric arc. Due to complex furnace phenomena and the wide variety of potential scenarios, high performance computing (HPC) is essential to yield comprehensive and detailed CFD analyses and systematic parametric studies for optimized EAF operation. The objectives are to 1) simulate scrap melting using electric arc, 2) evaluate electrode/arc position for optimum scrap melting and 3) establish reduced order model for CFD data-base for fast model calculation.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2025

Fiscal Year 2025 Software Quality Assurance Activities for the ARC Software

The continued goal of the ARC SQA project in the Advanced Reactor Technologies program of DOE is to resolve the QA gaps for the ARC software that limit, or prevent, commercialization of the software for industry users. This project started in earnest in fiscal year 2023 which saw the entire code system moved from a SVN repository to a GitLab repository and an associated software quality assurance plan (SQAP) developed and ratified. Most of the QA gaps in the ARC software were identified in collaboration with industry partners and work begin in fiscal year 2023 and continued through 2024 and 2025. The continuous integration testing was extended to RCT, DASSH, and SE2ANL. Minor changes were required to the original continuous integration methodology to make this happen. When full confidence in the methodology is complete, a report will be created to detail the automated regression testing methodology and minor reports will be created to detail the tolerance settings that have been applied to the output for each ARC code. The primary documentation that is missing includes user manuals, user guides, software verification reports, and code coverage assessments. The DASSH, SE2ANL, and SE2RCT manuals were completed this fiscal year. A review of the SE2ANL software identified that it is unrealistic to include updated correlations or different geometry models and it was scheduled for deprecation in favor of DASSH. The SE2ANL manual is essential for SE2RCT as they are similar but quite different in purpose. The only piece of software missing a manual consistent with the source code is NUBOW-3D which is a focus of the coming year. The code coverage report for DIF3D was updated and code coverage reports were created for REBUS, RCT, PERSENT, GAMSRC, and DASSH. Minor coverage issues were identified for all of these pieces of software which did not prevent the work done to transition them to the OneAPI compiler. Because SE2ANL was scheduled for deprecation, it was not transitioned, but it was successfully tested with the OneAPI compiler. This leaves SE2RCT and NUBOW-3D as the only pieces of software not transitioned to OneAPI and further work is required to get SE2RCT to work properly. The SE2RCT software transition will begin early next year while the NUBOW-3D software requires a manual before it can begin. Software verification work has been completed for DIF3D, REBUS, GAMSOR, GAMSRC, VARPOW, EvaluateFlux, and SUMMAR. The PERSENT software verification work was completed this year which was somewhat delayed because of unexpected bugs in the software. The PERSENT manual was updated to detail some of the issues and discuss the bowing reactivity worth feature added in the previous fiscal year. The RCT, DASSH, SE2RCT, and NUBOW-3D software are the only maintained pieces of software without verification reports. The software verification work for DASSH will be a focus in the upcoming fiscal year and it is hoped that some of the test cases created can serve as verification tests for SE2RCT. The NUBOW-3D work will begin when the manual and requirements report are completed. Only minor industry partner software development funds were provided this year. The DASSH software was updated to handle general axial geometry for each assembly and the NUBOW-3D software was updated to incorporate a new input format and better output. Overall progress on resolving the QA gaps has been good this year.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2025

Fiscal Year 2025 Software Quality Assurance Activities for the ARC Software

The continued goal of the ARC SQA project in the Advanced Reactor Technologies program of DOE is to resolve the QA gaps for the ARC software that limit, or prevent, commercialization of the software for industry users. This project started in earnest in fiscal year 2023 which saw the entire code system moved from a SVN repository to a GitLab repository and an associated software quality assurance plan (SQAP) developed and ratified. Most of the QA gaps in the ARC software were identified in collaboration with industry partners and work begin in fiscal year 2023 and continued through 2024 and 2025. The continuous integration testing was extended to RCT, DASSH, and SE2ANL. Minor changes were required to the original continuous integration methodology to make this happen. When full confidence in the methodology is complete, a report will be created to detail the automated regression testing methodology and minor reports will be created to detail the tolerance settings that have been applied to the output for each ARC code. The primary documentation that is missing includes user manuals, user guides, software verification reports, and code coverage assessments. The DASSH, SE2ANL, and SE2RCT manuals were completed this fiscal year. A review of the SE2ANL software identified that it is unrealistic to include updated correlations or different geometry models and it was scheduled for deprecation in favor of DASSH. The SE2ANL manual is essential for SE2RCT as they are similar but quite different in purpose. The only piece of software missing a manual consistent with the source code is NUBOW-3D which is a focus of the coming year. The code coverage report for DIF3D was updated and code coverage reports were created for REBUS, RCT, PERSENT, GAMSRC, and DASSH. Minor coverage issues were identified for all of these pieces of software which did not prevent the work done to transition them to the OneAPI compiler. Because SE2ANL was scheduled for deprecation, it was not transitioned, but it was successfully tested with the OneAPI compiler. This leaves SE2RCT and NUBOW-3D as the only pieces of software not transitioned to OneAPI and further work is required to get SE2RCT to work properly. The SE2RCT software transition will begin early next year while the NUBOW-3D software requires a manual before it can begin. Software verification work has been completed for DIF3D, REBUS, GAMSOR, GAMSRC, VARPOW, EvaluateFlux, and SUMMAR. The PERSENT software verification work was completed this year which was somewhat delayed because of unexpected bugs in the software. The PERSENT manual was updated to detail some of the issues and discuss the bowing reactivity worth feature added in the previous fiscal year. The RCT, DASSH, SE2RCT, and NUBOW-3D software are the only maintained pieces of software without verification reports. The software verification work for DASSH will be a focus in the upcoming fiscal year and it is hoped that some of the test cases created can serve as verification tests for SE2RCT. The NUBOW-3D work will begin when the manual and requirements report are completed. Only minor industry partner software development funds were provided this year. The DASSH software was updated to handle general axial geometry for each assembly and the NUBOW-3D software was updated to incorporate a new input format and better output. Overall progress on resolving the QA gaps has been good this year.

97 MATHEMATICS AND COMPUTING↗

NASA NTRS1974

Atmospheric spreading of protons in auroral arcs

A model is developed to calculate the effect of atmospheric spreading on the flux and angular distribution of protons in homogeneous auroral arcs. An expression is derived that indicates the angular distribution in the atmosphere as a function of distance from arc center, neutral scale height, arc width, and initial angular distribution. The results of the model agree favorably with those based on Monte-Carlo calculations. From these results the enhancement factors needed to compute the original proton current above the atmosphere are obtained. A technique is indicated for determining the incident angular distribution from rocket-based measurements of the arc width and angular distribution.

Iglesias, G. E.↗

NASA NTRS1974

On the nature of plasma arcs in solar active regions

A mechanism is proposed explaining the structures consisting of plasma arcs, as observed in X-ray photographs of solar active regions. It is suggested that the width of the arcs corresponds to the cut-off wavelength of a Rayleigh-Taylor instability which develops due to a difference in density between the plasma in the arcs and the plasma in the surrounding region. The transverse component of the magnetic field necessary to stabilize the instability at a wavelength corresponding to the width of the arcs is estimated to be of the order of 0.1 gauss.

Gajewski, R.↗

NASA NTRS1974

Is the red arc a good indicator of ionosphere-magnetosphere conditions

Weak red arcs were observed on the two consecutive nights of July 12-13 and July 13-14, 1969, at Richland, Washington, whereas no red arcs were detectable on the nights preceding and following the observations. Satellite (Ogo 6) data of electron temperature and density, low-frequency ac electric field, and suprathermal electron flux corresponding to the conjugate region of Richland show no significant variations during these days. The data show elevated electron temperatures and enhanced low-frequency ac noise levels at the expected red arc position in the neighborhood of the density trough, as indicated by previous observations. The data appear to indicate that the optical criterion of red arc occurrence would lead to the conclusion of significantly different ionosphere-magnetosphere conditions during these four nights, whereas the more detailed in situ data show that the conditions were very similar.

Nagy, A. F.↗

NASA NTRS1975

The SAR arc event observed during the December 1971 magnetic storm

Observations from five separate experiments on the Isis 2 spacecraft are used to study the atmosphere/ionosphere during the magnetic storm of December 16-20, 1971. The data are most complete in the midlatitude region, permitting a study of the SAR arc (subauroral red arc) which developed during the night of December 17-18. Ion composition and temperature, electron temperature, electron-density height profiles from the spacecraft to the F region, and the intensity of the 6300-A oxygen emission are all presented for the region of interest. It is found that the H(+) concentration had sharp gradients near the SAR arc and that the plasma temperature was significantly enhanced over typical nighttime values, reaching nearly 7000 K at 1400 km on the field line which intersected the arc. A system of time-dependent equations for atmospheric/ionospheric composition and temperature is solved using boundary conditions which were selected so that the solutions are in agreement with the observations. From these solutions, an assessment is made of the influence of (1) the efflux of plasma from the ionosphere to the magnetosphere, (2) the decrease in O/N2 at the turbopause, (3) the increase in the loss coefficient as a result of an increase in the vibrational temperature of N2, and (4) the conduction of thermal energy into the ionosphere.

Maier, E. J.↗

NASA NTRS1976

Simultaneous observations of the proton ring current and stable auroral red arcs

Explorer 45 observed the equatorial proton ring current in the plasmapause region and Fritz Peak Observatory observed stable auroral red (SAR) arcs on Dec. 17, 1971 during a geomagnetic storm. An estimate of energy lost from the ring current was obtained by using Explorer 45 observations of pitch angle distribution transitions which are probably due to pitch angle diffusion-driven resonant interactions with ion cyclotron waves. Estimates of the equatorial loss rate yield values greater than the required SAR arc energy input rate, and the location of the peaks in these loss rates agrees with the observed location of the arcs. It is thus concluded that this energy loss is sufficient to sustain the SAR arcs.

Williams, D. J.↗

NASA NTRS1976

Ionospheric composition in SAR-arcs

Theoretical ion and electron density profiles in the SAR-arc region are calculated using a model of the ionosphere based on the coupled continuity, momentum, and energy equations for O(+), NO(+), and O2(+). It is found that an increase in the reaction O(+) + N2 yields NO(+) + N, which results from enhanced N2 vibrational excitation due to the high electron temperatures found in SAR arcs, can cause a reduction in F-region electron densities by up to a factor of two. The increase in the O(+) + N2 reaction rate is shown to result in a marked change in the ion composition in SAR arcs, with NO(+) being an important ion up to altitudes of about 350 km at night. Since observed electron-density depressions in SAR arcs generally vary between factors of two and seven, it is concluded that the increase in the O(+) + N2 reaction rate cannot account for these depressions by itself.

Raitt, W. J.↗

NASA NTRS1976

The dc arc characteristics in subsonic orifice nozzle flow

The cold air flow field for a 1/27 cm orifice nozzle was determined for subsonic flow velocities. In addition, d.c. arc voltage, current, and diameter measurements were made for a range of velocities and arc gaps. Average voltage gradients increased rapidly as an arc extinguishing velocity was approached. Measured values of current and diameter were used as an input for relaxation solution of an energy balance equation to compute radial temperature profiles. Calculated arc voltage gradients compare favorably with measured average voltage gradients.

Nagamatsu, H. T.↗

NASA NTRS1977

Vacuum ultraviolet radiometry. III - The argon mini-arc as a new secondary standard of spectral radiance

A miniature argon arc has been designed and tested as a new transfer standard of spectral radiance for the wavelength range from 114 nm to 330 nm. Calibration has been performed using two primary standard sources: the hydrogen arc from 130 nm to 330 nm and the blackbody line radiator from 114 nm to 130 nm. The mini-arc provides an intense, stable, and reproducible UV continuum with dc power requirements of less than 1.5 kW. The arc characteristics have been investigated, and the sensitivity of the radiant power output to various operating parameters has been measured. The rms uncertainty in the spectral radiance is estimated to be 5.3% above 140 nm and 10.1% between 114 nm and 140 nm, due primarily to uncertainties in the primary standard sources.

Bridges, J. M.↗

NASA NTRS1978

Detached auroral arcs in the trough region

In a previous paper, Moshupi et al. (1977) have reported on the occurrence of rare auroral 'patches' equatorward of the normally well-defined boundary of diffuse aurora. Some less spectacular but more common arclike features were observed in the same 'trough' region (between the plasmapause and the auroral oval) during the period 1972-1975. These 'detached' arcs show some similarities to stable auroral red arcs in terms of their location and occurrence, but are completely different spectroscopically in that the stable auroral red arcs produce almost pure atomic oxygen red line emissions, whereas the detached arcs are deficient in red line emission - a feature implying totally different production mechanisms. The characteristics of the detached lines are described, including their unusual local time/longitude dependence.

Anger, C. D.↗

NASA NTRS1978

Effects of arcing due to spacecraft charging on spacecraft survival

A quantitative assessment of the hazard associated with spacecraft charging and arcing on spacecraft systems is presented. A literature survey on arc discharge thresholds and characteristics was done and gaps in the data and requirements for additional experiments were identified. Calculations of coupling of arc discharges into typical spacecraft systems were made and the susceptibility of typical spacecraft to disruption by arc discharges was investigated. Design guidelines and recommended practices to reduce or eliminate the threat of malfunction and failures due to spacecraft charging/arcing were summarized.

Rosen, A.↗

NASA NTRS1980

'GAIM' - Gas-addition, impedance-matched arc driver

A conceptual view for a GAIM energy/driver system to maximize shock-tube performance through efficient interfacing of the energy source with the gas dynamics of the arc driver is presented. Electrical and arc-chamber requirements are evaluated utilizing two new computer codes. One code calculates the shock wave generated for a selected time rate and magnitude of arc-energy input; the other computes the values of external circuit elements required to produce the selected energy input, with the driver represented as the load element of the electrical discharge circuit. Results indicate that the energy-storage capability and the driver arrangement needed to produce the highest shock Mach number can be achieved by means of driver gas addition and by impedance matching (GAIM). Design criteria are presented for arc energy requirements necessary to produce given shock-wave speeds. Shock velocities as high as the 70 km/sec required for simulating Jovian entry now seem possible in shock-tube operation. Practical implementation of a GAIM system is discussed.

Dannenberg, R. E.↗