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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Mass distributions of dijet resonances from excited quarks at proton-proton colliders

We study the expected experimental mass distributions of dijet resonances from excited quarks in proton-proton collisions at energies $\sqrt{s}$ = 13, 14, 27, 100, 300, and 500 TeV. We explore in detail the expected shapes at both the generator and experimental levels, and identify within the distributions the effects of the excited quark natural width, parton momentum distributions of the proton, radiation, and experimental resolution. We present both differential and cumulative probability distributions as a function of dijet mass, and the signal acceptance of a window in dijet mass centered on each resonance. We find that for a range of resonance masses, between 10% and 50% of $\sqrt{s}$, the dijet mass distributions and window acceptance are practically universal, approximately invariant under changes in resonance mass and $\sqrt{s}$. This universality is violated when the resonance mass reaches 60% of $\sqrt{s}$, because the steepness of the parton momentum distributions of the proton produces a significant tail at low dijet mass. This work supports our Snowmass 2021 study on the sensitivity to dijet resonances at proton-proton colliders.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

First measurement of the forward rapidity gap distribution in pPb collisions at $\sqrt{s_{NN}}$ = 8.16 TeV

For the first time at LHC energies, the forward rapidity gap spectra from proton-lead collisions for both proton and lead dissociation processes are presented. The analysis is performed over 10.4 units of pseudorapidity at a center-of-mass energy per nucleon pair of $\sqrt{s_{NN}}$ = 8.16 TeV , almost 300 times higher than in previous measurements of diffractive production in proton-nucleus collisions. For lead dissociation processes, which correspond to the pomeron-lead event topology, the EPOS-LHC generator predictions are a factor of 2 below the data, but the model gives a reasonable description of the rapidity gap spectrum shape. For the pomeron-proton topology, the EPOS-LHC , QGSJET II , and HIJING predictions are all at least a factor of 5 lower than the data. The latter effect might be explained by a significant contribution of ultraperipheral photoproduction events mimicking the signature of diffractive processes. These data may be of significant help in understanding the high energy limit of quantum chromodynamics and for modeling cosmic ray air showers.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Direct functionalization of C-H bonds by electrophilic anions

Bond formation between two of the most inert molecules, alkanes and [B12X12]2- (X = Cl, Br), is performed in a two step process. Fragmentation of [B12X12]2- in the gas phase generates highly reactive [B12X11]- ions which spontaneously react with alkanes. The reaction mechanism was investigated using tandem mass spectrometry and gas-phase vibrational spectroscopy combined with electronic structure calculations. This effort revealed the unprecedented and counterintuitive electrophilic substitution of a proton in an alkane by a negatively charged ion resulting in a B-C bond formation. The product is a dianionic [B12X11CnH2n+1]2- species, in which H+ is electrostatically bound to the dianion. High flux ion soft-landing was performed to co-deposit [B12X11]- and complex organic molecules (phthalates) in thin layers on surfaces. Molecular structure analysis of the product films revealed that C-H functionalization by [B12X11]- occured in the presence of other more reactive functional groups. This observation demonstrates the utility of highly reactive fragment ions for defined bond formation processes and may pave the way to the use of gas phase ion chemistry for chemical synthesis in the condensed phase.

Warneke, Jonas↗
NASA NTRS1988

A description of electron heating with an electrostatic potential jump in a parallel, collisionless, fire hose shock

The electron heating required if protons scatter elastically in a parallel, collisionless shock is calculated. Near-elastic proton scattering off large amplitude background magnetic field fluctuations might be expected if the waves responsible for the shock dissipation are generated by the fire hose instability. The effects of an electrostatic potential jump in the shock layer are included by assuming that the energy lost by protons in traversing the potential jump is converted into electron thermal pressure. It is found that the electron temperature increase is a strong function of the potential jump. Comparison is made to the parallel shock plasma simulation of Quest (1987).

Ellison, Donald C.↗
DOE OSTI2022

Elucidating the impact of the ionomer equivalent weight on a platinum group metal-free PEMFC cathode via oxygen limiting current

Leveraging the interactions between ionomer and catalyst can increase the performance of proton exchange membrane fuel cells. The impacts of the equivalent weight (EW) of perfluorosulfonic acid–based ionomers on the platinum group metal-free electrode structure and fuel cell performance have not been fully explored. Four membrane electrode assemblies (MEAs) were prepared by using a commercial Fe–N–C catalyst, two perfluorosulfonic acid ionomers with different EWs, that is, Aquivion 720 (A720) and Nafion 1100 (N1100), and two ionomer-to-catalyst (I/C) ratios. The four MEAs were characterized to understand the impact of the ionomer EW and content on the capacitance, proton conductivity, and mass transport on the cathode. The mass transport resistance was measured for the first time using a new oxygen reduction reaction limiting current method enabling to couple the effects of oxygen diffusion with liquid water generation. Low EW ionomer combined with a moderate I/C results in improved performance due to its enhanced proton conductivity. However, when used at high I/C, it can cause severe water flooding at high current density due to the enhanced liquid water uptake, especially at high relative humidity, resulting in lower catalyst utilization and higher mass transport resistance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Methodology to Generate the Decay Gamma Source for a Second Target Station Target Wedge

This report details the specifics of applying the Position-Averaged Method methodology for the calculation of the rotating lasagna-style target wedge activation and the resulting decay gamma source terms. The methodology uses MCNP® Code Version 6.2.0 with the RNUCS patch coupled with CINDER2008 from the AARE V1.0 package. The process begins with model preparations that include ensuring impurities are included in the materials in the regions of interest along with segmentation of the geometry in order to capture the decay gamma source gradients. This report also details the physics models and other MCNP®, CINDER2008, and ADVANTG 3.2.0 related options used to calculate the decay gamma source terms. ADVANTG 3.2.0 is used to generate a weight window set to aid in convergence of the neutron fluxes in the initial MCNP® protons-on-target particle transport calculation to calculate the neutron fluxes and spallation products in the regions of interest. The neutron fluxes and spallation products are then used in the CINDER2008 transmutation calculation, and the decay gamma sources are generated by the AARE_GAMMA_SOURCE_SCRIPT as a part of the AARE V1.0 package. These decay gamma sources include the energy distributions as well as the necessary distributions to sample the location of the source using the cell rejection method. The gamma sources that are produced using the methodology may be used for a wide variety of analysis involving the target wedge. This report includes the material specifications, physics options, proton source term description, geometrical configuration, and post-processing details.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Vector bosons and jets in proton collisions

Events with vector bosons produced in association with jets have been extensively studied at hadron colliders and provide high-accuracy tests of the standard model. A good understanding of these processes is of paramount importance for precision Higgs physics, as well as for searches for new physics. In particular, associated production of γ, W, or Z bosons with light-flavor and heavy-flavor jets is a powerful tool for testing perturbative QCD calculations, Monte Carlo event generators, and can also constrain the parametrizations used to describe the parton content of the proton. Furthermore, events with a W or Z boson produced with two well-separated jets can be used to distinguish between electroweak and strong production mechanisms, and to set limits on contributions of physics beyond the standard model. This review summarizes the historical theoretical developments and the state-of-the-art in the modeling of vector-boson-plus-jet physics while focusing on experimental results by the LHC collaborations in run 1 and run 2 and including comparisons with recent measurements at the Tevatron.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Probing the neutron-proton asymmetry dependence of the nuclear source temperature with light charged particles

The dependence of the nuclear temperature on the source neutron-proton (N/Z) asymmetry was experimentally investigated with the light charged particles (LCPs) generated from thirteen reaction systems with different N/Z asymmetries, 64 Zn on 112 Sn and 70 Zn, 64 Ni on 112,124 Sn, 58,64 Ni, 197 Au, 232 Th at 40 MeV/u. A rather weak N/Z asymmetry dependence of the source temperature was qualitatively inferred from the extracted N/Z asymmetry dependence of the apparent temperature and that of the relative temperature change by the sequential decay effects with the help of the theoretical simulations. Comparing the present result with those from our previous work and other available experimental results, a weak N/Z asymmetry dependence of nuclear temperature is commonly observed in different independent experiments and with different thermometers, except for the result reported by McIntosh et al. [Phys. Lett. B 719, 337 (2013)]. Here, the origin of the difference between the conclusion of the former group and that of McIntosh et al. was addressed, using statistical multifragmentation model (SMM) simulations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Lepton-nucleus cross section measurements for DUNE with the LDMX detector

We point out that the LDMX (Light Dark Matter eXperiment) detector design, conceived to search for sub-GeV dark matter, will also have very advantageous characteristics to pursue electron-nucleus scattering measurements of direct relevance to the neutrino program at DUNE and elsewhere. These characteristics include a 4-GeV electron beam, a precision tracker, electromagnetic and hadronic calorimeters with near 2 π azimuthal acceptance from the forward beam axis out to ~ 40 ° angle, and low reconstruction energy threshold. LDMX thus could provide (semi)exclusive cross section measurements, with detailed information about final-state electrons, pions, protons, and neutrons. We compare the predictions of two widely used neutrino generators ( genie , g i buu ) in the LDMX region of acceptance to illustrate the large modeling discrepancies in electron-nucleus interactions at DUNE-like kinematics. We argue that discriminating between these predictions is well within the capabilities of the LDMX detector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Relative-Humidity Dependence of Electrochemically Active Surface Area in Porous Carbon Catalyst Layers

Polymer-electrolyte fuel cells (PEFCs) utilize porous catalyst layers (CLs) formed of carbon supports on which Pt particles are deposited and ionomer films are distributed. Carbon supports themselves have varying degrees of porosity, where high-surface-area carbon (HSC) supports possess nanometer-sized interior pores that are suitable for Pt nanoparticle deposition but prevent deleterious ionomer penetration. However, this requires protons to transport through water pathways inside the pores. To understand the generation of such pathways, we examine the various mechanisms of water uptake by PEFC CLs, and the subsequent impact of water uptake on Pt utilization through developing a multiphysics model of the water wetting phenomena as a function of relative humidity. The model details water uptake via ionomer absorption, capillary condensation in the hydrophilic pores, and surface adsorption using molecular potential that account for various water and surface dipole interactions. The results quantify how mesoporous carbons with highly hydrophilic pores increase Pt utilization through the development of wetted layers, which at the same time enable optimized gas-transport pathways. It also demonstrates the impact of pore-size distribution (PSD) and physical and chemical parameters on the water uptake phenomena, allowing for future CL particle and structure optimization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Bayesian Exploration and Surrogate Emulation of Nonlinear Beam-Response Geometry in the LBNF Beamline

Next-generation long-baseline neutrino experiments aim to achieve multi-MW proton beam power while reducing accelerator-induced systematic uncertainties. At Fermilab, the LBNF beamline is designed for 1.2 MW operation with PIP-II and is upgradeable to 2.4 MW. DUNE will probe the three-flavor neutrino paradigm and search for CP violation, requiring precise neutrino-flux normalization and improved control of accelerator-related uncertainties. Within the LBNF beamline, the System for On-Axis Neutrino Detection (SAND) will constrain flux uncertainties using precision near-detector measurements, while the Muon Monitor System (MuMS) will provide beamline diagnostics sensitive to the proton beam, target, and horn configuration. However, the pion phase space relevant for DUNE depends simultaneously on many correlated parameters, including beam centroid, beam width, horn current and alignment, target position, optics shifts, and radiation-induced changes. Consequently, MuMS observables exhibit nonlinear and coupled responses that are difficult to characterize using traditional one-parameter scans. To address this challenge, we are developing a Bayesian Exploration framework coupled to physics-informed surrogate emulators trained on Geant4 beamline simulations. Gaussian-process emulators provide both fast predictions and uncertainty estimates, enabling adaptive selection of new simulation points in beam-parameter space. As an initial demonstration, we construct surrogate emulators for MuMS response observables using a verified simulation campaign spanning proton-beam steering conditions. The emulators reproduce the simulated dependence of MuMS centroid and gradient observables while providing predictive uncertainties, and serve as the foundation for future multidimensional exploration including beam width, horn current, and additional beamline parameters. This work establishes a framework for uncertainty-aware beam monitoring, adaptive simulation campaigns, and rapid beam-response inference for future DUNE operations.

Ganguly, Sudeshna [Fermilab] (ORCID:00000003163482↗
DOE OSTI2020

Cryogenic Liquid Jets for High Repetition Rate Discovery Science

In this paper, we present a detailed procedure for the operation of continuous, micron-sized cryogenic cylindrical and planar liquid jets. When operated as described here, the jet exhibits high laminarity and stability for centimeters. Successful operation of a cryogenic liquid jet in the Rayleigh regime requires a basic understanding of fluid dynamics and thermodynamics at cryogenic temperatures. Theoretical calculations and typical empirical values are provided as a guide to design a comparable system. This report identifies the importance of both cleanliness during cryogenic source assembly and stability of the cryogenic source temperature once liquefied. The system can be used for high repetition rate laser-driven proton acceleration, with an envisioned application in proton therapy. Other applications include laboratory astrophysics, materials science, and next-generation particle accelerators.

42 ENGINEERING↗
NASA NTRS1982

Radiation effects studies for the high-resolution spectrograph

The generation and collection of charge carriers created during the passage of energetic protons through a silicon photodiode array are modeled. Pulse height distributions of noise charge collected during exposure of a digicon type diode array to 21 and 75 MeV protons were obtained. The magnitude of charge collected by a diode from each proton event is determined not only by diffusion, but by statistical considerations involving the ionization process itself. Utilizing analytical solutions to the diffusion equation for transport of minority carriers, together with the Vavilov theory of energy loss fluctuations in thin absorbers, simulations of the pulse height spectra which follow the experimental distributions fairly well are presented and an estimate for the minority carrier diffusion length L sub d is provided.

Smith, L. C.↗
NASA NTRS1997

Lower Hybrid Oscillations in Multicomponent Space Plasmas Subjected to Ion Cyclotron Waves

It is found that in multicomponent plasmas subjected to Alfven or fast magnetosonic waves, such as are observed in regions of the outer plasmasphere and ring current-plasmapause overlap, lower hybrid oscillations are generated. The addition of a minor heavy ion component to a proton-electron plasma significantly lowers the low-frequency electric wave amplitude needed for lower hybrid wave excitation. It is found that the lower hybrid wave energy density level is determined by the nonlinear process of induced scattering by ions and electrons; hydrogen ions in the region of resonant velocities are accelerated; and nonresonant particles are weakly heated due to the induced scattering. For a given example, the light resonant ions have an energy gain factor of 20, leading to the development of a high-energy tail in the H(+) distribution function due to low-frequency waves.

Khazanov, G. V.↗
NASA NTRS2002

Spatiotemporal Variability and Propagation of Equatorial Noise Observed by Cluster

We report a multipoint case study of the electromagnetic equatorial noise observed by the Cluster project. High-resolution data were measured in three close points in space located in the morning sector of the outer plasmasphere. We demonstrate a narrow latitudinal extent of the emissions with a typical width of 2 degrees, centered near the minimum-B equator. Power spectra recorded by the different satellites show a complex structure of emission lines whose relative intensities and positions vary at timescales of 1-2 min and/or at spatial scales of tens of wavelengths. These lines do not match harmonics of the local proton cyclotron frequency, as it would be expected if the waves are generated by energetic ions and observed near the source region. We bring observational evidence that the waves propagate with a significant radial component and thus can propagate from a distant generation region located at different radial distances where ion cyclotron frequencies match the observed fine structure.

Santolik, O.↗
NASA NTRS2003

Durability of Membrane Electrode Assemblies (MEAs) in PEM Fuel Cells Operated on Pure Hydrogen and Oxygen

Proton exchange membrane (PEM) fuel cells are energy sources that have the potential to replace alkaline fuel cells for space programs. Broad power ranges, high peak-to-nominal power capabilities, low maintenance costs, and the promise of increased life are the major advantages of PEM technology in comparison to alkaline technology. The probability of PEM fuel cells replacing alkaline fuel cells for space applications will increase if the promise of increased life is verified by achieving a minimum of 10,000 hours of operating life. Durability plays an important role in the process of evaluation and selection of MEAs for Teledyne s Phase I contract with the NASA Glenn Research Center entitled Proton Exchange Membrane Fuel cell (PEMFC) Power Plant Technology Development for 2nd Generation Reusable Launch Vehicles (RLVs). For this contract, MEAs that are typically used for H2/air operation were selected as potential candidates for H2/O2 PEM fuel cells because their catalysts have properties suitable for O2 operation. They were purchased from several well-established MEA manufacturers who are world leaders in the manufacturing of diverse products and have committed extensive resources in an attempt to develop and fully commercialize MEA technology. A total of twelve MEAs used in H2/air operation were initially identified from these manufacturers. Based on the manufacturers specifications, nine of these were selected for evaluation. Since 10,000 hours is almost equivalent to 14 months, it was not possible to perform continuous testing with each MEA selected during Phase I of the contract. Because of the lack of time, a screening test on each MEA was performed for 400 hours under accelerated test conditions. The major criterion for an MEA pass or fail of the screening test was the gas crossover rate. If the gas crossover rate was higher than the membrane intrinsic permeability after 400 hours of testing, it was considered that the MEA had failed the test. Three types of MEAs out of the nine total membranes failed the test. The evaluation results showed that fuel cell operating conditions (current, pressure, stoichiometric flow rates) were the parameters that influenced the durability of MEAs. In addition, the durability test results indicated that the type of membrane was also an important parameter for MEA durability. At accelerated test conditions, the MEAs with casted membranes failed during the 400 hour test. However, the MEAs prepared from the casted membrane with support as well as extruded membranes, both passed the 400h durability test at accelerated operating test conditions. As a result of the MEA accelerated durability tests, four MEAs were selected for further endurance testing. These tests are being carried out with four-cell stacks under nominal fuel cell operating conditions.

Stanic, Vesna↗
NASA NTRS2004

Environment of Space Interactions with Space Systems

The primary product of this research project was a computer program named SAVANT. This program uses the Displacement Damage Dose (DDD) method of calculating radiation damage to solar cells. This calculation method was developed at the Naval Research Laboratory, and uses fundamental physical properties of the solar cell materials to predict radiation damage to the solar cells. This means that fewer experimental measurements are required to characterize the radiation damage to the cells, which results in a substantial cost savings to qualify solar cells for orbital missions. In addition, the DDD method makes it easier to characterize cells that are already being used, but have not been fully tested using the older technique of characterizing radiation damage. The computer program combines an orbit generator with NASA's AP-8 and AE-8 models of trapped protons and electrons. This allows the user to specify an orbit, and the program will calculate how the spacecraft moves during the mission, and the radiation environment that it encounters. With the spectrum of the particles, the program calculates how they would slow down while traversing the coverglass, and provides a slowed-down spectrum.

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