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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

The ray-tracing code Zgoubi - latest developments

The reader is referred to the ICFA-BD-NL No.43, and to a more recent status article in NIMA, regarding the technical details of the Zgoubi tracking engine and its accuracy, which make it "near-symplectic" - sufficiently so to model millions of turns in large hadron colliders, - and its potential for pushing particles in complex accelerator structures and accelerator optical elements or their field maps. Extended documentation can be found in the regular FFA workshops as well as in the SourceForge code development site where in particular many examples of beam lines, FFAs and other ring simulations are maintained. There is also a comprehensive user's guide. Further documentation, including an attempt to demonstrate 6D simulation in all possible types of particle accelerators, can be found in the "Computer Laboratory" Stony Brook University "PHY689" semester series.

43 PARTICLE ACCELERATORS↗
NASA NTRS1987

Simulations of the sun's polar magnetic fields during sunspot cycle 21

Regarding new bipolar magnetic regions as sources of flux, the evolution of the radial component of the solar photospheric magnetic field is simulated during 1976-1984, and the corresponding evolution of the line-of-sight polar fields as seen from earth is derived. The observed timing and strength of the polar-field reversal during cycle 21 can be accounted for by supergranular diffusion alone, for a diffusion coefficient of 800 sq km/sec. For an assumed 300 sq km/sec rate of diffusion, on the other hand, a poleward meridional flow with a moderately broad profile and a peak speed of 10 m/s reached at about 5 deg latitude is required to obtain agreement between the simulated and observed fields. Such a flow accelerates the transport of following-polarity flux to the polar caps, but also inhibits the diffusion of leading-polarity flux across the equator. For flows faster than about 10 m/s, the latter effect dominates, and the simulated polar fields reverse increasingly later and more weakly than the observed fields.

Devore, C. Richard↗
DOE OSTI2018

Comparison between simulated and observed LHC beam backgrounds in the ATLAS experiment at E beam =4 TeV

Results of dedicated Monte Carlo simulations of beam-induced background (BIB) in the ATLAS experiment at the Large Hadron Collider (LHC) are presented and compared with data recorded in 2012. During normal physics operation this background arises mainly from scattering of the 4 TeV protons on residual gas in the beam pipe. Methods of reconstructing the BIB signals in the ATLAS detector, developed and implemented in the simulation chain based on the \textsc{Fluka} Monte Carlo simulation package, are described. The interaction rates are determined from the residual gas pressure distribution in the LHC ring in order to set an absolute scale on the predicted rates of BIB so that they can be compared quantitatively with data. Through these comparisons the origins of the BIB leading to different observables in the ATLAS detectors are analysed. The level of agreement between simulation results and BIB measurements by ATLAS in 2012 demonstrates that a good understanding of the origin of BIB has been reached.

47 OTHER INSTRUMENTATION↗
NASA NTRS2009

Telemetry-Enhancing Scripts

Scripts Providing a Cool Kit of Telemetry Enhancing Tools (SPACKLE) is a set of software tools that fill gaps in capabilities of other software used in processing downlinked data in the Mars Exploration Rovers (MER) flight and test-bed operations. SPACKLE tools have helped to accelerate the automatic processing and interpretation of MER mission data, enabling non-experts to understand and/or use MER query and data product command simulation software tools more effectively. SPACKLE has greatly accelerated some operations and provides new capabilities. The tools of SPACKLE are written, variously, in Perl or the C or C++ language. They perform a variety of search and shortcut functions that include the following: Generating text-only, Event Report-annotated, and Web-enhanced views of command sequences; Labeling integer enumerations with their symbolic meanings in text messages and engineering channels; Systematic detecting of corruption within data products; Generating text-only displays of data-product catalogs including downlink status; Validating and labeling of commands related to data products; Performing of convenient searches of detailed engineering data spanning multiple Martian solar days; Generating tables of initial conditions pertaining to engineering, health, and accountability data; Simplified construction and simulation of command sequences; and Fast time format conversions and sorting.

Maimone, Mark W.↗
NASA NTRS1992

Physical and digital simulations for IVA robotics

Space based materials processing experiments can be enhanced through the use of IVA robotic systems. A program to determine requirements for the implementation of robotic systems in a microgravity environment and to develop some preliminary concepts for acceleration control of small, lightweight arms has been initiated with the development of physical and digital simulation capabilities. The physical simulation facilities incorporate a robotic workcell containing a Zymark Zymate II robot instrumented for acceleration measurements, which is able to perform materials transfer functions while flying on NASA's KC-135 aircraft during parabolic manuevers to simulate reduced gravity. Measurements of accelerations occurring during the reduced gravity periods will be used to characterize impacts of robotic accelerations in a microgravity environment in space. Digital simulations are being performed with TREETOPS, a NASA developed software package which is used for the dynamic analysis of systems with a tree topology. Extensive use of both simulation tools will enable the design of robotic systems with enhanced acceleration control for use in the space manufacturing environment.

Hinman, Elaine↗
DOE OSTI2017

Space-Charge Simulation of Integrable Rapid Cycling Synchrotron

Integrable optics is an innovation in particle accelerator design that enables strong nonlinear focusing without generating parametric resonances. We use a Synergia space-charge simulation to investigate the application of integrable optics to a high-intensity hadron ring that could replace the Fermilab Booster. We find that incorporating integrability into the design suppresses the beam halo generated by a mismatched KV beam. Our integrable rapid cycling synchrotron (iRCS) design includes other features of modern ring design such as low momentum compaction factor and harmonically canceling sextupoles. Experimental tests of high-intensity beams in integrable lattices will take place over the next several years at the Fermilab Integrable Optics Test Accelerator (IOTA) and the University of Maryland Electron Ring (UMER).

43 PARTICLE ACCELERATORS↗
NASA NTRS2014

Energetic Electrons in Dipolarization Events: Spatial Properties and Anisotropy

Using the electromagnetic fields of an MHD simulation of magnetotail reconnection, flow bursts, and dipolarization, we further investigate the acceleration of electrons to suprathermal energies. Particular emphasis is on spatial properties and anisotropies as functions of energy and time. The simulation results are compared with Time History of Events and Macroscale Interactions during Substorms observations. The test particle approach successfully reproduces several observed injection features and puts them into a context of spatial maps of the injection region(s): a dominance of perpendicular anisotropies farther down the tail and closer to the equatorial plane, an increasing importance of parallel anisotropy closer to Earth and at higher latitudes, a drop in energy fluxes at energies below approximately 10 keV, coinciding with the plasma density drop, together with increases at higher energy, a triple peak structure of flux increases near 0 deg, 90 deg, and 180 deg, and a tendency of flux increases to extend to higher energy closer to Earth and at lower latitudes. We identified the plasma sheet boundary layers and adjacent lobes as a main source region for both increased and decreased energetic electron fluxes, related to the different effects of adiabatic acceleration at high and low energies. The simulated anisotropies tend to exceed the observed ones, particularly for perpendicular fluxes at high energies. The most plausible reason is that the MHD simulation lacks the effects of anisotropy-driven microinstabilities and waves, which would reduce anisotropies.

anisotropy↗
DOE OSTI2024

Beam-induced backgrounds measured in the ATLAS detector during local gas injection into the LHC beam vacuum

Inelastic beam-gas collisions at the Large Hadron Collider (LHC), within a few hundred metres of the ATLAS experiment, are known to give the dominant contribution to beam backgrounds. These are monitored by ATLAS with a dedicated Beam Conditions Monitor (BCM) and with the rate of fake jets in the calorimeters. These two methods are complementary since the BCM probes backgrounds just around the beam pipe while fake jets are observed at radii of up to several metres. In order to quantify the correlation between the residual gas density in the LHC beam vacuum and the experimental backgrounds recorded by ATLAS, several dedicated tests were performed during LHC Run 2. Local pressure bumps, with a gas density several orders of magnitude higher than during normal operation, were introduced at different locations. The changes of beam-related backgrounds, seen in ATLAS, are correlated with the local pressure variation. In addition the rates of beam-gas events are estimated from the pressure measurements and pressure bump profiles obtained from calculations. Using these rates, the efficiency of the ATLAS beam background monitors to detect beam-gas events is derived as a function of distance from the interaction point. These efficiencies and characteristic distributions of fake jets from the beam backgrounds are found to be in good agreement with results of beam-gas simulations performed with theFluka Monte Carlo programme.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Role of Direct Laser Acceleration of Electrons in a Laser Wakefield Accelerator with Ionization Injection

We show the first experimental demonstration that electrons being accelerated in a laser wakefield accelerator operating in the forced or blowout regimes gain significant energy from both the direct laser acceleration (DLA) and the laser wakefield acceleration mechanisms. Supporting full-scale 3D particle-in-cell simulations elucidate the role of the DLA of electrons in a laser wakefield accelerator when ionization injection of electrons is employed. An explanation is given for how electrons can maintain the DLA resonance condition in a laser wakefield accelerator despite the evolving properties of both the drive laser and the electrons. The produced electron beams exhibit characteristic features that are indicative of DLA as an additional acceleration mechanism.

43 PARTICLE ACCELERATORS↗
NASA NTRS1992

Effects of near-Earth stochastic acceleration and reflections of magnetotail ions on the formation of auroral arcs

Findings obtained from global kinetic simulations of magnetotail plasma are discussed. A region of strongly nonadiabatic ion acceleration (known as the 'wall' region) exists in the near earth tail and demarcates two very different regimes of ion motion: adiabatic and quasi-adiabatic. After convection through the wall, ion distributions rapidly become isotropized and thermalized. A strong enhancement of the cross tail current occurs on the tailward side of the wall. Comparison of numerical and adiabatic pressure profiles indicates that nonadiabatic processes operating in this region may contribute significantly to a pressure balance relief in the course of quasi-steady magnetospheric convection.

Ashour-Abdalla, Maha↗
DOE OSTI2014

Low-Z linac targets for low-MV gold nanoparticle radiation therapy

Purpose: To investigate the potential of low-Z/low-MV (low-Z) linac targets for gold nanoparticle radiotherapy (GNPT) and to determine the microscopic dose enhancement ratio (DER) due to GNP for the alternative beamlines. In addition, to evaluate the degradation of dose enhancement arising from the increased attenuation of x rays and larger skin dose in water for the low-MV beams compared to the standard linac. Methods: Monte Carlo simulations were used to compute dose and DER for various flattening-filter-free beams (2.5, 4, 6.5 MV). Target materials were beryllium, diamond, and tungsten-copper high-Z target. Target thicknesses were selected based on 20%, 60%, 70%, and 80% of the continuous slowing down approximation electron ranges for a given target material and energy. Evaluation of the microscopic DER was carried out for 100 nm GNP including the degradation factors due to beam attenuation. Results: The greatest increase in DER compared to the standard 6.5 MV linac was for a 2.5 MV Be-target (factor of ∼2). Skin dose ranged from ∼10% (Be, 6.5 MV-80%) to ∼85% (Be, 2.5 MV-20%) depending on the target case. Attenuation of 2.5 MV beams at 22 cm was higher by ∼75% compared with the standard beam. Taking into account the attenuation at 22 cm depth, the effective dose enhancement was up to ∼60% above the DER of the high-Z target. For these cases the effective DER ranged between ∼1.6 and 6 compared with the standard linac. Conclusions: Low-Z (2.5 MV) GNPT is possible even after accounting for greater beam attenuation for deep-seated tumors (22 cm) and the increased skin dose. Further, it can lead to significant sparing of normal tissue while simultaneously escalating the dose in the tumor cells.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2013

Simulation of Betatron X-Ray Radiation as an Indirect Measurement of Electron Trajectories in a Laser-Wakefield Accelerator

Laser-wakefield accelerators (LWFA) only a few centimeters long have generated ultrarelativistic electrons and synchrotron-like x-rays. One barrier to using LWFA's for accelerator and x-ray source applications is the current inability to directly measure and characterize the betatron oscillations of electrons in the plasma. We have developed Mathematica/MATLAB simulations to model betatron oscillations and x-ray generation in a LWFA. By fitting simulation parameters to obtain closest agreement with experimentally measured betatron x-ray beam profiles, we obtain indirect measurements of experimental electron trajectories.

42 ENGINEERING↗
NASA NTRS2005

Turbulence Hazard Metric Based on Peak Accelerations for Jetliner Passengers

Calculations are made of the approximate hazard due to peak normal accelerations of an airplane flying through a simulated vertical wind field associated with a convective frontal system. The calculations are based on a hazard metric developed from a systematic application of a generic math model to 1-cosine discrete gusts of various amplitudes and gust lengths. The math model simulates the three degree-of- freedom longitudinal rigid body motion to vertical gusts and includes (1) fuselage flexibility, (2) the lag in the downwash from the wing to the tail, (3) gradual lift effects, (4) a simplified autopilot, and (5) motion of an unrestrained passenger in the rear cabin. Airplane and passenger response contours are calculated for a matrix of gust amplitudes and gust lengths. The airplane response contours are used to develop an approximate hazard metric of peak normal accelerations as a function of gust amplitude and gust length. The hazard metric is then applied to a two-dimensional simulated vertical wind field of a convective frontal system. The variations of the hazard metric with gust length and airplane heading are demonstrated.

Stewart, Eric C.↗
DOE OSTI2014

Comparisons of dosimetric accuracy and calculation time of ARCHER and MCNP5 codes for the Ir-192 brachytherapy case - Paper 1

In the last decade, the graphics processing unit (GPU) technology has emerged as a viable player in high-performance computing. A GPU card is designed to carry out thousands of single instructions simultaneously, showing unprecedented computing power when compared with the traditional CPU technology. It has been proved that some computationally intensive programs can be accelerated drastically on the GPUs including Monte Carlo simulations. Unfortunately, existing production Monte Carlo codes cannot be easily ported to the GPU environment. To address the needs, a new Monte Carlo code ARCHER (Accelerated Radiation-transport Computations in Heterogeneous Environment) is being developed at Rensselaer Polytechnic Institute, employing the latest GPU and the Intel Xeon Phi coprocessor technologies. We can execute the code which was written using C and C++ on both CPU and GPU platforms. The ARCHER GPU code was written in CUDA C 5.0 and was tested on the Tesla M2090. There have been a few studies testing the ARCHER GPU code on several different platforms. In particular, Su et al has tested the ARCHER for external-beam radiation treatment 20 MeV monoenergetic monodirectional parallel electron beam. The comparison of the calculation results between EGSnrc and ARCHERGPU was impressive. A remarkable 224- fold speed-up factor was obtained using a NVIDIA Tesla M2090 GPU compared to a CPU. In this study, we applied the ARCHER code to dose calculation for a relatively new procedure, called accelerated partial breast irradiation (APBI) brachytherapy. The APBI brachytherapy dose calculation was based on RPI-AF phantom which is a 3D heterogeneous patient model. We then compared the dosimetric accuracy and calculation times of ARCHER and MCNP5 to gain insight into the accuracy and speedup of the GPU-based ARCHER code. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗
NASA NTRS1996

Analysis of Residual Acceleration Effects on Transport and Segregation During Directional Solidification of Tin-Bismuth in the MEPHISTO Furnace Facility

The objective of this work is to approach the problem of determining the transport conditions (and effects of residual acceleration) during the plane-front directional solidification of a tin-bismuth alloy under low gravity conditions. The work involves using a combination of 2- and 3-D numerical models, scaling analyses, ID models and the results of ground-based and low-gravity experiments. The latter are to be conducted during the MEPHISTO experiment scheduled for USMP-3 in early 1996. The models will be used to predict the response of the transport conditions and consequent solute segregation in directionally solidifying tin-bismuth melt. Real-time Seebeck voltage variations across a Sn-Bi melt during directional solidification in MEPHISTO on USMP-1 show a distinct variation which can be correlated with thruster firings. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-solid interface. This allows a direct comparison of numerical simulations with the Seebeck signals obtained on USMP-1. The effects of such accelerations on composition for a directionally solidifying Sn-Bi alloy have been simulated numerically. USMP-1 acceleration data was used to assist in our choice of acceleration magnitude and orientation. The results show good agreement with experimental observations. The USMP-3 experiments took place earlier this year (February 22 through March 6). There were several differences between the USMP-3 experiments as compared to USMP-1. Firstly a more concentrated alloy was solidified and, secondly, Primary Reaction Control System thruster burns were requested at particular times during four separate growth runs. This allowed us to monitor the response Seebeck response under well-characterized growth conditions. In addition, we carried out simulations during the experiment in order to interpret the Seebeck signal. Preliminary results are described here.

Alexander J. Iwan D.↗
DOE OSTI2023

Studying performance portability of LAMMPS across diverse GPU-based platforms

The molecular dynamics simulation software, LAMMPS, utilizes the Kokkos acceleration library to port computation to a diverse set of architectures including those based on GPU accelerators. In addition to Kokkos, LAMMPS contains a vast code base that leverages the CUDA application programming interface using library functions such as cuFFT, CUDA's fast-fourier transform (FFT) library, and, more recently, also support for AMD's Heterogeneous Interface for Portability (HIP) that is rapidly growing. While preparing LAMMPS tests for the AMD GPU-based test system precursors to Frontier, we investigated several strategies for accelerating LAMMPS on AMD GPUs, using the AMD Instinct MI100 and MI250X. In this work, we integrated the HIP FFT library, hipFFT, into the particle-particle particle-mesh (PPPM) long-range solver, which allowed the porting of PPPM calculations to the GPUs. Kokkos behavior on the MI100 and MI250X was also investigated through the package kokkos command of LAMMPS, targeting communication, memory usage, and particle grid decomposition. The Tersoff, Reax, Lennard-Jones (LJ), EAM, Granular, and PPPM potentials were investigated in this effort, and results from these experiments are provided. In conclusion, the selected potentials were run on Spock (AMD Instinct MI100), Crusher (AMD Instinct MI250X), AFW HPC11 (NVIDIA A100) and Summit (NVIDIA V100), for comparison. Operational roofline models were constructed and analyzed for the Tersoff, Reax, and Lennard–Jones potentials on Crusher and Summit.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Computational models of direct and indirect X‐ray breast imaging detectors for in silico trials

Abstract Background To facilitate in silico studies that investigate digital mammography (DM) and breast tomosynthesis (DBT), models replicating the variety in imaging performance of the DM and DBT systems, observed across manufacturers are needed. Purpose The main purpose of this work is to develop generic physics models for direct and indirect detector technology used in commercially available systems, with the goal of making them available open source to manufacturers to further tweak and develop the exact in silico replicas of their systems. Methods We recently reported on an in silico version of the SIEMENS Mammomat Inspiration DM/DBT system using an open‐source GPU‐accelerated Monte Carlo x‐ray imaging simulation code (MC‐GPU). We build on the previous version of the MC‐GPU codes to mimic the imaging performances of two other Food and Drug Administration (FDA)‐approved DM/DBT systems, such as Hologic Selenia Dimensions (HSD) and the General Electric Senographe Pristina (GSP) systems. In this work, we developed a hybrid technique to model the optical spread and signal crosstalk observed in the GSP and HSD systems. MC simulations are used to track each x‐ray photon till its first interaction within the x‐ray detector. On the other hand, the signal spread in the x‐ray detectors is modeled using previously developed analytical equations. This approach allows us to preserve the modeling accuracy offered by MC methods in the patient body, while speeding up secondary carrier transport (either electron–hole pairs or optical photons) using analytical equations in the detector. The analytical optical spread model for the indirect detector includes the depth‐dependent spread and collection of optical photons and relies on a pre‐computed set of point response functions that describe the optical spread as a function of depth. To understand the capabilities of the computational x‐ray detector models, we compared image quality metrics like modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE), simulated with our models against measured data. Please note that the purpose of these comparisons with measured data would be to gauge if the model developed as part of this work could replicate commercially used direct and indirect technology in general and not to achieve perfect fits with measured data. Results We found that the simulated image quality metrics such as MTF, NNPS, and DQE were in reasonable agreement with experimental data. To demonstrate the imaging performance of the three DM/DBT systems, we integrated the detector models with the VICTRE pipeline and simulated DM images of a fatty breast model containing a spiculated mass and a calcium oxalate cluster. In general, we found that the images generated using the indirect model appeared more blurred with a different noise texture and contrast as compared to the systems with direct detectors. Conclusions We have presented computational models of three commercially available FDA‐approved DM/DBT systems, which implement both direct and indirect detector technology. The updated versions of the MC‐GPU codes that can be used to replicate three systems are available in open source format through GitHub.

Sengupta, Aunnasha↗
DOE OSTI2025

Atomistic Simulations of Thermal and Chemical Expansions of PrNi x Co 1‐x O 3‐δ Accelerated by Machine Learning Potentials

The electrodes and solid-state electrolytes in protonic ceramic electrochemical cells (PCECs) experience significant lattice expansions when exposed to high steam concentrations at elevated temperatures. In this paper, phonon calculations based on a new machine learning potential (MLP) are employed to elucidate the volume expansions of the proton-conducting PrNi x Co 1-x O 3-δ (PNC) lattices, manifested under a combined influence of oxygen vacancies (V$^{\cdot\cdot}_O$ ) and proton uptake (OH$^{\cdot}_O$ ) in the bulk at varying Ni/Co occupancies. It is revealed that the Ni/Co occupancy contributes to thermal and chemical expansions differently, where thermal expansions are related to Co occupancy. In contrast, chemical expansions are more closely associated with the Ni occupancy. Both V$^{\cdot\cdot}_O$ and OH$^{\cdot}_O$ lead to higher thermal expansions when compared to the pristine PNC. The temperature increase will negatively impact the hydration-induced chemical expansions. For combined thermal and chemical expansions, it is predicted that the strategies that boost the PCEC's electrochemical performance may harm the electrode–electrolyte interfacial stability, when the Ni occupancy is high, due to severe chemical expansions. Mitigating chemical expansions of the Ni-abundant PNC will benefit the interfacial stability. Finally, the presented computational methods for phonon calculations, based on emerging machine learning interatomic potential techniques are anticipated to have a lasting impact on future PCEC development.

computational prediction↗