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DOE OSTI2024

On the measurement of shape: With applications to lunar regolith

With the renewed commitment from NASA and other commercial entities for a presence on the Moon, the importance of understanding the characteristics of lunar regolith and how to utilize it have become the target of increasing scrutiny. Much of what is known about lunar regolith was collected during and immediately after the Apollo program, however, analytical techniques and instrumentation have advanced in leaps and bounds in the subsequent decades. Specifically, dynamic image analysis systems have advanced to the point that millions of particles can have morphological characteristics automatically determined in relatively short time frames. Particle morphological data was collected on several lunar samples and a pair of widely used regolith simulants to ascertain the accuracy of these simulants and to explore statistical analysis methods of these large datasets. It is found that these morphology datasets can vary widely depending on the particle size of the particles, and simple averaging of the data skews the results heavily towards the numerically abundant size ranges, the fines. Different reporting methods are suggested to ameliorate these problems. When applied to the lunar regolith, the particles are noted to be less morphologically complex than initially suspected. Compared to the lunar material, the simulants are found to contain some more morphological variability and angular grains. Such difference is likely due to the wildly different comminution processes that these different powder systems are subjected to.

2D shape↗

DOE OSTI2011

{chi}{sup 2} versus median statistics in supernova type Ia data analysis

In this paper we compare the performances of the {chi}{sup 2} and median likelihood analysis in the determination of cosmological constraints using type Ia supernovae data. We perform a statistical analysis using the 307 supernovae of the Union 2 compilation of the Supernova Cosmology Project and find that the {chi}{sup 2} statistical analysis yields tighter cosmological constraints than the median statistic if only supernovae data is taken into account. We also show that when additional measurements from the cosmic microwave background and baryonic acoustic oscillations are considered, the combined cosmological constraints are not strongly dependent on whether one applies the {chi}{sup 2} statistic or the median statistic to the supernovae data. This indicates that, when complementary information from other cosmological probes is taken into account, the performances of the {chi}{sup 2} and median statistics are very similar, demonstrating the robustness of the statistical analysis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2013

Gaussian Lagrangian stochastic models for multi-particle dispersion

We have extended the “well-mixed” two-particle stochastic models for 3D Gaussian turbulence to n particles, and have performed calculations for clusters of n ≤ 6 particles. The particle joint motions are Gaussian and are constrained by pair-wise spatial correlations. This neglects non-Gaussian properties of the two-point velocity distribution and also neglects multi-point correlations. It also takes no account of intermittency. Although the models do not predict the growth of the separation of particles in the cluster satisfactorily, we find that they do give a good representation of the shape statistics for the cluster in comparison with direct numerical simulation results. We conclude that the pair-wise spatial structure of the turbulence accounts for most of the observed characteristics of the shape of multi-particle clusters in turbulence, and that non-Gaussian and multi-point features of the turbulence are of secondary importance.

42 ENGINEERING↗

DOE OSTI2016

Characterization of the Geosynchronous Plasma Environment for the SENSER/RROE Optical Instrument

In this report, we summarize available research in order to characterize expected rates of particle incidence on the SENSER/RROE optical instrument. We first investigate the “normal” background levels using data from statistical studies of spacecraft in geosynchronous orbit and empirical models. We then consider “worst case” scenarios based on event studies in which extreme fluxes have been observed. We use these data to define “maximum” rates of particle incidence. We then consider how incident particles will actually produce counts in the instrument by considering the effects of screening by the instrument housing and the possibility of direct particle access to the housing, with rates for both primary access and secondary electron generation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS2013

Evaluation of Low-Gravity Smoke Particulate for Spacecraft Fire Detection

Tests were conducted on the International Space Station to evaluate the smoke particulate size from materials and conditions that are typical of those expected in spacecraft fires. Five different materials representative of those found in spacecraft (Teflon, Kapton, cotton, silicone rubber and Pyrell) were heated to temperatures below the ignition point with conditions controlled to provide repeatable sample surface temperatures and air flow. The air flow past the sample during the heating period ranged from quiescent to 8 cm/s. The effective transport time to the measurement instruments was varied from 11 to 800 seconds to simulate different smoke transport conditions in spacecraft. The resultant aerosol was evaluated by three instruments which measured different moments of the particle size distribution. These moment diagnostics were used to determine the particle number concentration (zeroth moment), the diameter concentration (first moment), and the mass concentration (third moment). These statistics were combined to determine the diameter of average mass and the count mean diameter and by assuming a log-normal distribution, the geometric mean diameter and the geometric standard deviations were also calculated. Smoke particle samples were collected on TEM grids using a thermal precipitator for post flight analysis. The TEM grids were analyzed to determine the particle morphology and shape parameters. The different materials produced particles with significantly different morphologies. Overall the majority of the average smoke particle sizes were found to be in the 200 to 400 nanometer range with the quiescent cases and the cases with increased transport time typically producing with substantially larger particles. The results varied between materials but the smoke particles produced in low gravity were typically twice the size of particles produced in normal gravity. These results can be used to establish design requirements for future spacecraft smoke detectors.

Fire Safety↗

NASA NTRS2013

Evaluation of Low-Gravity Smoke Particulate for Spacecraft Fire Detection

Fire↗

DOE OSTI2019

Secondary Vertexing in REDTOP Experiment Simulations

The η/η’ mesons are almost unique in the particle universe since they are Goldstone bosons and the dynamics of their decays are strongly constrained. Because the η/η’ have no charge, decays that violate conservation laws can occur without interfering with a corresponding current. The integrated eta meson samples collected in earlier experiments have been less than ~10 9 events, limiting considerably the search for such rare decays. The η’ sample is even more scarce. REDTOP (Rare Eta Decays with a TPC for Optical Photons) is being proposed at the proton booster of Fermilab with the intent of collecting more than 10 15 triggers/year for studies of rare η/η’ decays. Such statistics are sufficient for investigating several symmetry violations, and for searches for new particles beyond the Standard Model. This following project is most concerned with the detection of such new particles by way of the identification of detached, secondary vertices.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

Development of an inertial confinement fusion platform to study charged particle-producing nuclear reactions relevant to nuclear astrophysics

This paper describes the development of a platform to study astrophysically relevant nuclear reactions using inertial-confinement fusion implosions on the OMEGA and NIF laser facilities, with a particular focus on optimizing the implosions to study charged-particle-producing reactions. Primary requirements on the platform are high yield, for high statistics in the fusion product measurements, combined with low areal density, to allow the charged fusion products to escape. This is optimally achieved with direct-drive exploding pusher implosions using thin-glass-shell capsules. Mitigation strategies to eliminate a possible target sheath potential which would accelerate the emitted ions are discussed. The potential impact of kinetic effects on the implosions is also considered. The platform is initially employed to study the complementary T(t,2n)??, T(3He,np)?? and 3He(3He,2p)?? reactions. Proof-of-principle results from the first experiments demonstrating the ability to accurately measure the energy and yields of charged particles are presented. Lessons learned from these experiments will be used in studies of other reactions. The goals are to explore thermonuclear reaction rates and fundamental nuclear physics in stellar-like plasma environments, and to push this new frontier of nuclear astrophysics into unique regimes not reachable through existing platforms, with thermal ion velocity distributions, plasma screening and low reactant energies.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2010

Statistical quark models for the nucleon structure functions

We consider some existing relativistic models for the nucleon structure functions, relying on statistical approaches instead of perturbative ones. These models are based on the Fermi-Dirac distribution for the confined quarks, where a density of energy levels is obtained from an effective confining potential. In this context, it is presented some results obtained with a recent statistical quark model for the sea-quark asymmetry in the nucleon. It is shown, within this model, that experimental available observables, such as the ratio and difference between proton and neutron structure functions, are quite well reproduced with just three parameters: two chemical potentials used to reproduce the valence up and down quark numbers in the nucleon, and a temperature that is being used to reproduce the Gottfried sum rule violation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Complete Development of Critical Capabilities for TRISO Fission Product Source Term Calculations and Quantify Mechanisms for Pd Penetration of SiC

Overall fission product (FP) release will be an important consideration for the licensing and deployment of advanced reactors utilizing tristructural isotropic (TRISO) fuels. This work focuses on enhancing and applying the BISON models needed to predict FP transport within TRISO particles and particle failure probability, both of which factor directly into release predictions. Specifically, this report details (1) the development of the models needed to predict palladium (Pd) conservation at the engineering scale and the application of those models to characterize Pd fluxes for input into a mechanistic multiscale model for Pd penetration; (2) the refinement of sorption mass transfer models and the development of models for trapping in porous layers, which were applied and compared to particle scans from AGR-2 to provide proof of concept for a method of particle-scale validation that may reduce uncertainties compared to compact-scale validation using data from integral effects tests; (3) the development of a failure-statistics-informed, mesh-independent methodology for applying smeared cracking, enabling further study of the localized multiphysics behaviors associated with cascading particle failure mechanisms; and (4) the preliminary characterization of those coupled multiphysics particle failure behaviors using smeared, nonretentive diffusivities to provide a baseline for future study and to guide ongoing engineering applications.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2019

Most theoretical approaches used in nuclear astrophysics to model the nucleosynthesis of heavy elements incorporate the so-called statistical model in order to describe the excitation and decay properties of atomic nuclei. One of the basic assumptions of this model is the validity of the Brink–Axel hypothesis and the related concept of so-called photon strength functions to describe γ-ray transition probabilities. We present a novel experimental approach that allows for the first time to experimentally determine the photon strength function simultaneously in two independent ways by a unique combination of quasi-monochromatic photon beams and a newly implemented γ–γ coincidence setup. This technique does not assume a priori the validity of the Brink–Axel hypothesis and sets a benchmark in terms of the detection sensitivity for measuring decay properties of photo-excited states below the neutron separation energy. The data for the spherical off-shell nucleus 128 Te were obtained for γ-ray beam-energy settings between 3 MeV and 9 MeV in steps of 130 keV for the lower beam energies and in steps of up to 280 keV for the highest beam settings. We present a quantitative analysis on the consistency of the derived photon strength function with the Brink–Axel hypothesis. The data clearly demonstrate a discrepancy of up to a factor of two between the photon strength functions extracted from the photoabsorption and photon emission process, respectively. In addition, we observe that the photon strength functions are not independent of the excitation energy, as usually assumed. Thus, we conclude, that the Brink–Axel hypothesis is not strictly fulfilled in the excitation-energy region below the neutron separation threshold (S n = 8.78 MeV) for the studied case of 128 Te.

Not Available

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Development of an inertial confinement fusion platform to study charged-particle-producing nuclear reactions relevant to nuclear astrophysics

Here, this paper describes the development of a platform to study astrophysically relevant nuclear reactions using inertial-confinement fusion implosions on the OMEGA and National Ignition Facility laser facilities, with a particular focus on optimizing the implosions to study charged-particle- producing reactions. Primary requirements on the platform are high yield, for high statistics in the fusion product measurements, combined with low areal density, to allow the charged fusion products to escape. This is optimally achieved with direct-drive exploding pusher implosions using thin-glass-shell capsules. Mitigation strategies to eliminate a possible target sheath potential which would accelerate the emitted ions are discussed. The potential impact of kinetic effects on the implosions is also considered. The platform is initially employed to study the complementary T(t,2n)α, T( 3 He,np)α and 3 He( 3 He,2p)α reactions. Proof-of-principle results from the first experiments demonstrating the ability to accurately measure the energy and yields of charged particles are presented. Lessons learned from these experiments will be used in studies of other reactions. Ultimately, the goals are to explore thermonuclear reaction rates and fundamental nuclear physics in stellarlike plasma environments, and to push this new frontier of nuclear astrophysics into unique regimes not reachable through existing platforms, with thermal ion velocity distributions, plasma screening, and low reactant energies.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2016

Observation and characterization of a cosmic muon neutrino flux from the northern hemisphere using six years of IceCube data

The IceCube Collaboration has previously discovered a high-energy astrophysical neutrino flux using neutrino events with interaction vertices contained within the instrumented volume of the IceCube detector. We present a complementary measurement using charged current muon neutrino events where the interaction vertex can be outside this volume. As a consequence of the large muon range the effective area is significantly larger but the field of view is restricted to the Northern Hemisphere. IceCube data from 2009 through 2015 have been analyzed using a likelihood approach based on the reconstructed muon energy and zenith angle. At the highest neutrino energies between 194 TeV and 7.8 PeV a significant astrophysical contribution is observed, excluding a purely atmospheric origin of these events at 5.6σ significance. The data are well described by an isotropic, unbroken power-law flux with a normalization at 100 TeV neutrino energy of (0.90{sub −0.27}{sup +0.30})×10{sup −18} GeV{sup −1} cm{sup −2} s{sup −1} sr{sup −1} and a hard spectral index of γ=2.13±0.13. The observed spectrum is harder in comparison to previous IceCube analyses with lower energy thresholds which may indicate a break in the astrophysical neutrino spectrum of unknown origin. The highest-energy event observed has a reconstructed muon energy of (4.5±1.2) PeV which implies a probability of less than 0.005% for this event to be of atmospheric origin. Analyzing the arrival directions of all events with reconstructed muon energies above 200 TeV no correlation with known γ-ray sources was found. Using the high statistics of atmospheric neutrinos we report the current best constraints on a prompt atmospheric muon neutrino flux originating from charmed meson decays which is below 1.06 in units of the flux normalization of the model in Enberg et al.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

One-dimensional pion, kaon, and proton femtoscopy in Pb-Pb collisions at s NN = 2.76 TeV

The size of the particle emission region in high-energy collisions can be deduced using the femtoscopic correlations of particle pairs at low relative momentum. Such correlations arise due to quantum statistics and Coulomb and strong final state interactions. In this paper, results are presented from femtoscopic analyses of π ± π ± , K ± K ± , K$0\atop{S}$K$0\atop{S}$, pp , and $\overline{p}$ $\overline{p}$ correlations from Pb-Pb collisions at s NN = 2.76 TeV by the ALICE experiment at the LHC. One-dimensional radii of the system are extracted from correlation functions in terms of the invariant momentum difference of the pair. The comparison of the measured radii with the predictions from a hydrokinetic model is discussed. The pion and kaon source radii display a monotonic decrease with increasing average pair transverse mass m T which is consistent with hydrodynamic model predictions for central collisions. Lastly, the kaon and proton source sizes can be reasonably described by approximate m T scaling.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2018

Phase separation of self-propelled ballistic particles

Self-propelled particles phase-separate into coexisting dense and dilute regions above a critical density. The statistical nature of their stochastic motion lends itself to various theories that predict the onset of phase separation. However, these theories are ill-equipped to describe such behavior when noise becomes negligible. To overcome this limitation, we present a predictive model that relies on two density-dependent timescales: $τ_F$, the mean time particles spend between collisions; and $τ_C$, the mean lifetime of a collision. We show that only when $τ_F$ < $τ_C$ do collisions last long enough to develop a growing cluster and initiate phase separation. Finally, using both analytical calculations and active particle simulations, we measure these timescales and determine the critical density for phase separation in both two and three dimensions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2010

Critical phenomena in high-energy lepton- and hadron-induced reactions

We argue that the nucleon seen in the Bjorken scaling region is a gas of quasi-free partons. As x decreases, for certain values of Q {sup 2} the partons in a nucleon coalesce to a liquid (saturation). Experimentally this phenomenon is manifested as the turn-over of the structure function derivatives. The phenomenon can be quantified in the framework of statistical models, percolation and other approaches to collective effects in the strongly interacting matter. Similarities and differences between the case of lepton-hadron, hadron-hadron and heavy-ion collisions are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

Plasmoid statistics in relativistic magnetic reconnection

Plasmoids, overdense blobs of plasma containing magnetic fields and high-energy particles, are a self-consistent outcome of the reconnection process in the relativistic regime. Recent two-dimensional particle-in-cell (PIC) simulations have shown that plasmoids can sustain a variety of processes (e.g. mergers, bulk acceleration, growth, and advection) within the reconnection layer. We developed a Monte Carlo code, benchmarked with the recent PIC simulations, to examine the effects of these processes on the steady-state size and momentum distributions of the plasmoid chain. The differential plasmoid size distribution is shown to be a power law, ranging from a few plasma skin depths to ~0.1 of the reconnection layer’s length. The power-law slope is shown to be linearly dependent upon the ratio of the plasmoid acceleration and growth rates, which slightly decreases with increasing plasma magnetization. We perform a detailed comparison of our results with those of recent PIC simulations and briefly discuss the astrophysical implications of our findings through the representative case of flaring events from blazar jets.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1976

Analysis of satellite data on energetic particles of ionospheric origin

The principal result of this program has been the completion of a detailed statistical study of the properties of precipitating O(+) and H(+) ions during two principal magnetic storms. The results of the analysis of selected data of ion mass spectrometer experiment on satellites are given with emphasis on the morphology of the O(+) ions of ionospheric origin with energies in the 0.7 les than or equal to E less than or equal to 12 keV range that were discovered with this experiment.

Sharp, R. D.↗