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At least 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Enhancing the efficiency of time-dependent density functional theory calculations of dynamic response properties

X-ray Thomson scattering (XRTS) constitutes an essential technique for diagnosing material properties under extreme conditions, such as high pressures and intense laser heating. Time-dependent density functional theory (TDDFT) is one of the most accurate available ab initio methods for modeling XRTS spectra, as well as a host of other dynamic material properties. However, strong thermal excitations, along with the need to account for variations in temperature and density as well as the finite size of the detector significantly increase the computational cost of TDDFT simulations compared to ambient conditions. In this work, we present a broadly applicable method for optimizing and enhancing the efficiency of TDDFT calculations. Our approach is based on a one-to-one mapping between the dynamic structure factor and the imaginary time density–density correlation function, which naturally emerges in Feynman’s path integral formulation of quantum many-body theory. Specifically, we combine rigorous convergence tests in the imaginary time domain with a constraints-based attenuation of narrow-band fluctuations to improve the efficiency of TDDFT modeling without the introduction of any significant bias. As a result, we can report a speed-up by up to an order of magnitude, thus substantially reducing the burden of computational cost required for XRTS analysis.

Moldabekov, Zhandos A. [Helmholtz-Zentrum Dresden-↗
DOE OSTI2017

A Web-based application for the collection, management and release of Alignment and Calibration configurations used in data processing at the Compact Muon Solenoid experiment

The Compact Muon Solenoid (CMS) experiment makes a vast use of alignment and calibration measurements in several data processing workflows: in the High Level Trigger, in the processing of the recorded collisions and in the production of simulated events for data analysis and studies of detector upgrades. A complete alignment and calibration scenario is factored in approximately three-hundred records, which are updated independently and can have a time-dependent content, to reflect the evolution of the detector and data taking conditions. Given the complexity of the CMS condition scenarios and the large number (50) of experts who actively measure and release calibration data, in 2015 a novel web-based service has been developed to structure and streamline their management. The cmsDbBrowser provides an intuitive and easily accessible entry point for the navigation of existing conditions by any CMS member, for the bookkeeping of record updates and for the actual composition of complete calibration scenarios. This paper describes the design, choice of technologies and the first year of usage in production of the cmsDbBrowser.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Speeding up particle track reconstruction using a parallel Kalman filter algorithm

One of the most computationally difficult problems expected for the High-Luminosity Large Hadron Collider (HL-LHC) is determining the trajectory of charged particles during event reconstruction. Algorithms used at the LHC today rely on Kalman filtering, which builds physical trajectories incrementally while incorporating material effects and error estimation. Recognizing the need for faster computational throughput, we have adapted Kalman-filter-based methods for highly parallel, many-core SIMD architectures that are now prevalent in high-performance hardware. In this paper, we discuss the design and performance of the improved tracking algorithm, referred to as mkFit. A key piece of the algorithm is the Matriplex library, containing dedicated code to optimally vectorize operations on small matrices. The physics performance of the mkFit algorithm is comparable to the nominal CMS tracking algorithm when reconstructing tracks from simulated proton-proton collisions within the CMS detector. We study the scaling of the algorithm as a function of the parallel resources utilized and find large speedups both from vectorization and multi-threading. mkFit achieves a speedup of a factor of 6 compared to the nominal algorithm when run in a single-threaded application within the CMS software framework.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Characterisations of the HinOTORI telescope with a three-color imager at Ali Observatory in Western Tibet

HinOTORI is a new telescope supported by an international collaboration project between China and Japan. It is a 50 centimeter telescope equipped with simultaneous three-color imagers (u',R C , and I C bands). It is located at Ali Observatory at an altitude of 5100m. Thanks to the high altitude and extreme dryness, Ali site is one of the most suitable sites for optical astrometry. HinOTORI telescope aims at detecting optical transients such as the counterparts of gravitational wave (GW) sources, supernovae, gamma-ray bursts (GRB) and so on. This paper describes the site information, design of simultaneous three-color optical layout, system instruments and whole control system. We also report some telescope characterisations for three bands (u'/R C /I C ) respectively, such as Hartmann constant (0.49"/0.56"/0.60"), best focus position (3.922/3.920/3.903 mm), PSF FWHM size (3.755/3.328/3.167pixels), total transmittance and limiting magnitude (15.69/17.57/17.05mag, 10 σ 30 seconds exposure time). With different airmass observation data, the atmospheric extinction coefficients of three bands (0.366/0.061/0.026) were also derived.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Constraining calculations of Pu 239 ( n , γ ) cross sections with multistep cascade γ -ray spectra measured at the DANCE facility

Measurements of multistep cascade gamma-ray spectra from several low-lying 1 + resonances in the Pu 239 ( n , γ ) reaction were made using the DANCE detector. The measured spectra are compared to spectra simulated using several models for the photon strength function and the nuclear level density, representing the first analysis of this nature on a fissile nucleus. In general, models of the photon strength function that included a strong M 1 “scissors mode” contribution coupled with a Gilbert-Cameron nuclear level density provided a reasonable description of the spectra. Simulations using photon strength functions and nuclear level densities specifically for Pu 240 , extracted by the Oslo method, resulted in a very good representation of the measured spectra. Neutron-capture cross section calculations that included the scissors mode provided a good estimate of the previously measured values, without additional normalization. However, the scissors-mode energy that produced the best description of the multistep cascade spectra was different from the value that best reproduced the capture cross section. In addition, the 〈 Γ γ 〉 inferred from the multistep cascade calculations was somewhat less than the tabulated value, which was determined from resonance analysis. Published by the American Physical Society 2025

Ullmann, J. L. (ORCID:0000000207784405)↗
DOE OSTI2010

Gravitational backreaction effects on the holographic phase transition

We study radion stabilization in the compact Randall-Sundrum model by introducing a bulk scalar field, as in the Goldberger and Wise mechanism, but (partially) taking into account the backreactions from the scalar field on the metric. Our generalization reconciles the radion potential found by Goldberger and Wise with the radion mass obtained with the so-called superpotential method where backreaction is fully considered. Moreover we study the holographic phase transition and its gravitational wave signals in this model. The improved control over backreactions opens up a large region in parameter space and leads, compared to former analysis, to weaker constraints on the rank N of the dual gauge theory. We conclude that, in the regime where the 1/N expansion is justified, the gravitational wave signal is detectable by LISA.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Possible Explanation of the Geograv Detector Signal during the Explosion of SN 1987A in Modified Gravity Models

A change in the law of attraction in some regimes is predicted in the modified gravity models being actively developed at present. The set of up-to-date observational data leaves a wide range of admissible parameters for the theory. In this paper, we consider the possibility that the signal recorded by the Geograv resonant gravitational-wave detector in 1987 during the explosion of SN 1987A was produced by an abrupt change in the metric during the passage of a powerful neutrino flux through the detector. Such an impact on the detector is possible, in particular, in extended scalar–tensor theories in which the local matter density gradient affects the gravitational force. The first short neutrino pulse emitted at the initial stage of stellar core collapse before the onset of neutrino opacity could exert a major influence on the detector, because it could produce the detector response at the first resonance frequency. In contrast, the influence of the subsequent broad pulse (with a duration of several seconds) in the resonant detector is exponentially suppressed, despite the fact that the second pulse carries an order-of-magnitude more neutrino energy, and it could generate a signal in the LSD neutrino detector. This explains the time delay of 1.4 s between the Geograv and LSD signals. The consequences of this effect of modified gravity for future LIGO/Virgo observations are discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Measuring the energy deposited by muon bundles of inclined EAS in the NEVOD-DECOR experiment

As part of an in-depth investigation of the muon excess observed in ultrahigh-energy cosmic rays, one needs to measure the energy characteristics of muon component of extensive air showers (EAS). The mean muon energy can be estimated from the energy deposited in the detector by the muon bundles. In the NEVOD-DECOR experiment, the local muon density and the shower-arrival direction are measured with a track-coordinate detector, and the deposited energy is measured in the Cherenkov calorimeter. The results of the measurements carried out in 17400 h of detector operation are compared with those of the simulation based on the CORSIKA package.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Full simulation study of the top Yukawa coupling at the ILC at √s = 1 TeV

We present a study of the expected precision for the measurement of the top Yukawa coupling, y t , in e + e - collisions at a center-of-mass energy of 1 TeV. Independent analyses of tt-barH final states containing at least six hadronic jets are performed, based on detailed simulations of SiD and ILD, the two candidate detector concepts for the ILC. We estimate that a statistical precision on y t of 4.5 % can be obtained with an integrated luminosity of 1 ab -1 that is split equally between two configurations for the beam polarization P(e - ,e + ), (-80 %,+20 %) and (+80 %,-20 %). This estimate improves to 4 % if the 1 ab -1 sample is assumed to be fully in the P(e - ,e + )=(-80 %,+20 %) configuration.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

HexFinder

Simulations and analyses of data from hexagonally pixelated detectors require conversions from a Cartesian coordinate system to and from a hexagonal pixel index. This software builds and indexes the detector geometry, calculates neighbors and coordinate system conversions, and provides a framework for plotting analysis results.

Broussard, LeahJ.↗
DOE OSTI2025

Single-distance nano-holotomography with coded apertures

High-resolution phase-contrast 3D imaging using nano-holotomography typically requires collecting multiple tomograms at varying sample-to-detector distances, usually 3 to 4. This multi-distance approach limits temporal resolution, making it impractical for operando studies. Moreover, shifting the sample complicates reconstruction, requiring precise alignment, registration, and interpolation to correct for shift-dependent magnification on the detector. In response, we propose and validate through simulations a novel, to the best of our knowledge, single-distance approach that leverages coded apertures to structure beam illumination while the sample rotates. Finally, this approach relies on a joint reconstruction scheme, which integrates phase retrieval with 3D tomography, ensuring data consistency and achieving artifact-free reconstructions from a single distance, unlocking dynamic experiments.

Nikitin, Viktor [Argonne National Laboratory (ANL)↗
DOE OSTI2021

Cherenkov and Transition Radiation as Low-Energy Background Sources in SuperCDMS Detectors

The Weakly Interacting Massive Particle (WIMP) has historically been a prime candidate for dark matter due to its elegant compatibility with the Minimally Supersymmetric Standard Model (MSSM). Recent dark matter experiments have ruled out much of the GeV-TeV mass range predicted by the MSSM, however, and the newest generation of direct detection experiments, such as SuperCDMS SNOLAB, have begunto explore sub-GeV dark matter. As experiments push towards lower masses, sensitivity to eV-scale electron recoil events has become increasingly important. A variety of unexplained excesses at energy deposits of 1-100 eV have been found inmany such low-mass experiments, across different detection techniques and at different excess rates. These low-energy events are not thought to be dark matter, and they must be understood and effectively removed to further improve detector energy resolution. This thesis will outline the simulation of one possible source of low-energy excess at SuperCDMS: optical photons produced from charges in uniform motion, specifically from Cherenkov radiation (CR), transition radiation (TR), and the intermediate hybrid transition-Cherenkov radiation (HR). In the latter case, the standard formulae for HR contain divergences at certain angles in transparent media, which are an artifact of their derivation and become problematic to simulate. To rsolve this, we present a novel approach to normalize the divergent HR peaks, which allows HR to transition smoothly between TR and CR in a numerical simulation. We also add TR and CR as a physics process to the SuperCDMS Monte Carlo simulation package SuperSim, based on the Geant4 simulation toolkit. To verify the physics of our addition, we show some test simulations in comparison to theoretical predictions of optical radiation intensity. We also use the simulation to make some preliminary predictions on the contribution of TR and CR to the low energy background, with the expectation that more thorough analyses will be conducted in the future.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Science-Driven Candidate Search for New Scintillator Materials: FY 2014 Annual Report

This annual reports presents work carried out during Fiscal Year (FY) 2014 at Pacific Northwest National Laboratory (PNNL) under the project entitled “Science-Driven Candidate Search for New Scintillator Materials” (Project number: PL13-SciDriScintMat-PD05) and led by Drs. Fei Gao and Sebastien N. Kerisit. This project is divided into three tasks: 1) Ab initio calculations of electronic properties, electronic response functions and secondary particle spectra; 2) Intrinsic response properties, theoretical light yield, and microscopic description of ionization tracks; and 3) Kinetics and efficiency of scintillation: nonproportionality, intrinsic energy resolution, and pulse shape discrimination. Detailed information on the results obtained in each of the three tasks is provided in this Annual Report. Furthermore, peer-reviewed articles published this FY or currently under review and presentations given this FY are included in Appendix. This work was supported by the National Nuclear Security Administration, Office of Nuclear Nonproliferation Research and Development (DNN R&D/NA-22), of the U.S. Department of Energy (DOE).

scintillation, nonproportionality, Monte Carlo sim↗
DOE OSTI2017

The Nature of Scatter at the DARHT Facility and Suggestions for Improved Modeling of DARHT Facility

The U.S. Stockpile Stewardship Program [1] is designed to sustain and evaluate the nuclear weapons stockpile while foregoing underground nuclear tests. The maintenance of a smaller, aging U.S. nuclear weapons stockpile without underground testing requires complex computer calculations [14]. These calculations in turn need to be verified and benchmarked [14]. A wide range of research facilities have been used to test and evaluate nuclear weapons while respecting the Comprehensive Nuclear Test-Ban Treaty (CTBT) [2]. Some of these facilities include the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, the Z machine at Sandia National Laboratories, and the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory. This research will focus largely on DARHT (although some information from Cygnus and the Los Alamos Microtron may be used in this research) by modeling it and comparing to experimental data. DARHT is an electron accelerator that employs high-energy flash x-ray sources for imaging hydro-tests. This research proposes to address some of the issues crucial to understanding DARHT Axis II and the analysis of the radiographic images produced. Primarily, the nature of scatter at DARHT will be modeled and verified with experimental data. It will then be shown that certain design decisions can be made to optimize the scatter field for hydrotest experiments. Spectral effects will be briefly explored to determine if there is any considerable effect on the density reconstruction caused by changes in the energy spectrum caused by target changes. Finally, a generalized scatter model will be made using results from MCNP that can be convolved with the direct transmission of an object to simulate the scatter of that object at the detector plane. The region in which with this scatter model is appropriate will be explored.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2023

Developing Advanced Charge Readout Techniques for nEXO and Future Liquid Xenon OVBB Detectors (Final Report)

This award supported the Yale group’s efforts on nEXO, which included the following: 1) Developed techniques for measuring the outgassing of materials into liquid xenon (LXe) and a model for predicting the electron lifetime in nEXO and future LXe TPCs 2) Work to develop the conceptual design for the nEXO Photon Detector subsystem and TPC subsystem interconnections 3) Developed simulation of charge and light propagation and readout in nEXO.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Searching for the Nature of Dark Matter and Dark Energy

DE-SC0019474 supported a multi-pronged approach to understanding dark matter and dark energy. This included probes of dark matter at collider experiments, neutrino detectors, direct detection experiments, and N-body simulations of dark matter halos. This work helps guide our understanding of dark matter, particles associated with a dark matter sector, and how to use current and future experiments to search for direct evidence of dark matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Anomaly Detection In DUNE Using AI/ML

We designed and built an AI/ML model to detect anomalies in the DUNE far detector data. The model has been trained on simulated radiological background (rbkg) data, which is the major background for supernova burst neutrinos. The trained model was evaluated on both new samples of radiological backgrounds and supernova burst neutrino events in the elastic scattering and charged current interaction channels. We found that the trained model can successfully identify supernova burst neutrino events as anomalies while identifying radiological backgrounds as nominal events.

Novello, Eric [Unlisted, US]↗