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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Centrality determination with a forward detector in the RHIC Beam Energy Scan

Recently, Chatterjee et al [1] used a hadronic transport model to estimate the resolution with which various experimental quantities select the impact parameter of relativistic heavy ion collisions at collision energies relevant to the Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider (RHIC). Measures based on particle multiplicity at forward rapidity were found to be significantly worse than those based on midrapidity multiplicity. Using the same model, we show that a slightly more sophisticated measure greatly improves the resolution based on forward rapidity particles; this improvement persists even when the model is filtered through a realistic simulation of a recent upgrade detector to the STAR experiment. Furthermore, these results highlight the importance of optimizing centrality measures based on particles detected at forward rapidity, especially for experimental studies that search for a critical point in the QCD phase diagram. Such measurements usually focus on proton multiplicity fluctuations at midrapidity, hence selecting events based on multiplicity at midrapidity raises the possibility of nontrivial autocorrelations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Measurements of higher-order cumulants of multiplicity and net-electric charge distributions in inelastic proton-proton interactions by NA61/SHINE

This paper presents the energy dependence of multiplicity and net-electric charge fluctuations in p+p interactions at beam momenta 20, 31, 40, 80, and 158 \(\text{ Ge }\hspace{-1.00006pt}\text{ V }\!/\!c\). Results are corrected for the experimental biases and quantified with the use of cumulants and factorial cumulants. Cumulant ratios are an essential tool in the search for the critical point of strongly interacting matter in heavy ion collisions. Measurements performed in p+p interactions provide a vital baseline estimation in these studies. The measured signals are compared with the string hadronic models Epos1.99 and FTFP-BERT.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Kaon Femtoscopy with Lévy-Stable Sources from $\sqrt{s_{NN}}$ = 200 GeV Au+Au Collisions at RHIC

Femtoscopy has the capacity to probe the space-time geometry of the particle-emitting source in heavy-ion collisions. In particular, femtoscopy of like-sign kaon pairs may shed light on the origin of non-Gaussianity of the spatial emission probability density. The momentum correlations between like-sign kaon pairs are measured in data recorded by the STAR experiment, from $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions at RHIC, BNL. Preliminary results hint at the possible existence of non-Gaussian, Lévy-stable sources, with the likely presence of an anomalous diffusion process in the signal for the identically charged kaon pairs so produced. More statistically significant studies at lower centre-of-mass energies may contribute to the search for the critical end point of QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Far From Equilibrium Hydrodynamics and the Beam Energy Scan

The existence of hydrodynamic attractors in rapidly expanding relativistic systems has shed light on the success of relativistic hydrodynamics in describing heavy-ion collisions at zero chemical potential. As the search for the QCD critical point continues, it is important to investigate how out of equilibrium effects influence the trajectories on the QCD phase diagram. In this proceedings, we study a Bjorken expanding hydrodynamic system based on DMNR equations of motion with initial out of equilibrium effects and finite chemical potential in a system with a critical point. We find that the initial conditions are not unique for a specific freeze-out point, but rather the system can evolve to the same final state freeze-out point with a wide range of initial baryon chemical potential, µ B . For the same initial energy density and baryon density, depending on how far out of equilibrium the system begins, the initial µ B can vary by Δµ B ~ 350 MeV. Furthermore, our results indicate that knowledge of the out-of-equilibrium effects in the initial state provide vital information that influences the search for the QCD critical point.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Net-proton number fluctuations in the presence of the QCD critical point

Event-by-event fluctuations of the net-proton number studied in heavy-ion collisions provide an important means in the search for the conjectured critical end point (CP) in the QCD phase diagram. We propose a phenomenological model in which the fluctuations of the chiral critical mode couple to protons and anti-protons. This allows us to study the behavior of the net-proton number fluctuations in the presence of the CP. Calculating the net-proton number cumulants, Cn with n=1,2,3,4, along the phenomenological freeze-out line we show that the ratio of variance and mean C2/C1, as well as kurtosis C4/C2 resemble qualitative properties observed in data in heavy-ion collisions as a function of beam energy obtained by the STAR Collaboration at RHIC. In particular, the non-monotonic structure of the kurtosis and smooth change of the C2/C1 ratio with beam energy could be due to the CP located near the freeze-out line. The skewness, however, exhibits properties that are in contrast to the criticality expected due to the CP. The dependence of our results on the model parameters and the proximity of the chemical freeze-out to the critical point are also discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1987

TOMS: The Antarctic ozone hole and ozone trends

The Total Ozone Mapping Spectrometer (TOMS) instrument aboard Nimbus 7 has proved invaluable for the investigation of the recent rapid decline in the springtime total ozone over the Antarctic. The principle problem discussed is that of observing the atmosphere over long periods of time to determine whether or not trends and/or slow oscillations are taking place. Total ozone is an excellent summary parameter for the state of the stratosphere. It responds to temperature changes, and in the long term, is expected to respond to chemical changes. Thus, when changes take place in total ozone, such as the springtime Antarctic decrease it is a clear indication of an important problem, both because of environmental potential and scientific importance. TOMS is actually an overkill for this problem. Significantly more data is taken than is necessary. Tests have shown that maps produced on a 2 by 4 degree grid are essentially equivalent to those produced from the entire gridded data set. Because the critical aspect of the search for changes in ozone is continuous data, reflight of a polar orbiting TOMS is important. Included in the flight should be a stratospheric temperature sensor and, if possible, a modification to obtain some ozone altitude information. A critical aspect of the problem is timeliness of the data. This is the only drawback of the existing TOMS. It is expected that in the very near future the processing will be done within two weeks of real time. This is critical to the process of discovery of phenomena such as the Antarctic ozone hole.

Stolarski, Richard S.↗
DOE OSTI2022

A Fast and Accurate Transient Stability Assessment Method Based on Deep Learning: WECC Case Study

Transient stability is one of the critical aspects of power system stability assessment. The increasing integration of inverter-based resources and the retirement of conventional synchronous generators result in the decreasing system inertia and growing complexity of system operating conditions. Using a few selected typical operating conditions cannot guarantee system transient stability in all operating conditions, and the time-domain simulation of all operating conditions requires tremendous time and is often infeasible. This paper proposes a more efficient transient stability assessment method based on deep learning. The binary search method is used to determine the critical clearing time (CCT) in creating training databased by time-domain simulation. This method is fast and accurate with 1 ms resolution. The buses whose CCTs are lower than 200 ms are considered critical buses. Buses close to each other are grouped based on their mutual admittance matrix to reduce the search space of the critical buses. This paper also proposes the generator feature normalization based on the physical model. Case study on the reduced 240-bus WECC system model demonstrates that the proposed method can predict CCT accurately and efficiently.

critical clearing time↗
NASA NTRS1977

Searching for extraterrestrial civilizations

Three interrelated assumptions are critically examined in an attempt to outline a productive strategy for a search for extraterrestrial intelligence. Questions concerning the feasibility of interstellar travel are investigated. It is concluded that the probability of interstellar travel is high enough that, given a modest number of advanced civilizations, at least one of them will engage in interstellar voyages and colonize the galaxy. Assuming, however, that technological civilizations are rare the galaxy would be essentially unpopulated. Attention is given to the present lack of contact with extraterrestrial beings and frequencies for interstellar beacons.

Kuiper, T. B. H.↗
DOE OSTI2020

Revisiting the Role of Conductivity and Polarity of Host Materials for Long-Life Lithium–Sulfur Battery

Despite their high theoretical energy density and low cost, lithium-sulfur batteries (LSBs) suffer from poor cycle life and low energy efficiency owing to the polysulfides shuttle and the electronic insulating nature of sulfur. Conductivity and polarity are two critical parameters for the search of optimal sulfur host materials. However, their role in immobilizing polysulfides and enhancing redox kinetics for long-life LSBs are not fully understood. In this work we have conducted an evaluation on the role of polarity over conductivity by using a polar but nonconductive platelet ordered mesoporous silica (pOMS) and its replica platelet ordered mesoporous carbon (pOMC), which is conductive but nonpolar. It is found that the polar pOMS/S cathode with a sulfur mass fraction of 80 wt% demonstrates outstanding long-term cycle stability for 2000 cycles even at a high current density of 2C. Furthermore, the pOMS/S cathode with a high sulfur loading of 6.5 mg cm -2 illustrates high areal and volumetric capacities with high capacity retention. Complementary physical and electrochemical probes clearly show that surface polarity and structure are more dominant factors for sulfur utilization efficiency and long-life, while the conductivity can be compensated by the conductive agent involved as a required electrode material during electrode preparation. The present findings shed new light on the design principles of sulfur hosts towards long-life and highly efficient LSBs.

25 ENERGY STORAGE↗
DOE OSTI2023

Heavy neutral leptons at muon colliders

The future high-energy muon colliders, featuring both high energy and low background, could play a critical role in our searches for new physics. The smallness of neutrino mass is a puzzle of particle physics. Broad classes of solutions to the neutrino puzzles can be best tested by seeking the partners of SM light neutrinos, dubbed as heavy neutral leptons (HNLs), at muon colliders. We can parametrize HNLs in terms of the mass m N and the mixing angle with ℓ-flavor U ℓ . In this work, we focus on the regime m N > O(100) GeV and study the projected sensitivities on the |U ℓ | 2 – m N plane with the full-reconstructable HNL decay into a hadronic W and a charged lepton. The projected reach in |U ℓ | 2 leads to the best sensitivities in the TeV realm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Multiplicity scaling of light nuclei production in relativistic heavy-ion collisions

Using the nucleon coalescence model based on kinetic freeze-out nucleons from the 3D MUSIC+UrQMD and the 2D VISHNU hybrid model with a crossover equation of state, we study the multiplicity dependence of deuteron ( d ) and triton ( t ) production from central to peripheral Au+Au collisions at s NN = 7.7, 14.5, 19.6, 27, 39, 62.4 and 200 GeV and Pb+Pb at s NN = 2.76 TeV, respectively. It is found that the ratio N t N p / N d 2 of the proton yield N p , deuteron yield N d and triton yield N t exhibits a scaling behavior in its multiplicity dependence, i.e., decreasing monotonically with increasing charged-particle multiplicity. A similar multiplicity scaling of this ratio is also found in the nucleon coalescence calculation based on kinetic freeze-out nucleons from a multiphase transport (AMPT) model. The scaling behavior of N t N p / N d 2 can be naturally explained by the interplay between the sizes of light nuclei and the nucleon emission source. We further argue that the multiplicity scaling of N t N p / N d 2 can be used to validate the production mechanism of light nuclei, and the collision energy dependence of this yield ratio can further serve as a baseline in the search for the QCD critical point in relativistic heavy-ion collisions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Off-of-equilibrium effects on Kurtosis Along Strangeness-Neutral Trajectories

The Beam Energy Scan program at the Relativistic Heavy Ion Collider (RHIC) is searching for the QCD critical point. The main signal for the critical point is the kurtosis of the distribution of proton yields obtained on an event by event basis where one expects a peak at the critical point. However, its exact behavior is still an open question due to out-of-equilibrium effects and uncertainty in the equation of state. Here we use a simplistic hydrodynamic model that enforces strangeness-neutrality, selecting trajectories that pass close to the critical point. We vary the initial conditions to estimate the effect of out-of-equilibrium hydrodynamics on the kurtosis signal.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Beam-energy dependence of the production of light nuclei in Au + Au collisions

We study in the coalescence model the collision energy dependence of (anti-)deuteron and (anti- )triton production in the most central Au+Au collisions at $\sqrt{s_{NN}} $ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV. The needed phase-space distribution of nucleons at the kinetic freeze-out is generated from a new 3D hybrid dynamical model (iEBE-MUSIC) by using a smooth crossover equation of state (EoS) without a QCD critical point. Our model calculations predict that the coalescence parameters of (anti-)deuteron (B 2 (d) and B 2 ($\bar{d}$)) decrease monotonically as the collision energy increases, and the light nuclei yield ratio N t N p /$Nd^{2}_{d}$ remains approximately a constant with respect to the collision energy. These calculated observables fail to reproduce the non-monotonic behavior of the corresponding data from the STAR Collaboration. Without including any effects of the critical point in our model, our results serve as the baseline predictions for the yields of light nuclei in the search for the possible QCD critical points from the experimental beam energy scan of heavy ion collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Dynamics of non-Gaussian fluctuations in model A

Motivated by the experimental search for the QCD critical point, we perform simulations of a stochastic field theory with purely relaxational dynamics (model A). We verify the expected dynamic scaling of correlation functions. Using a finite size scaling analysis, we obtain the dynamic critical exponent z = 2.026(56). We investigate time dependent correlation functions of higher moments M n (t) of the order parameter M(t) for n = 1, 2, 3, 4. We obtain dynamic scaling with the same critical exponent z for all n, but the relaxation constant depends on n. We also study the relaxation of M n (t) after a quench, where the simulation is initialized in the high temperature phase, and the dynamics is studied at the critical temperature T c . Finally, we find that the evolution does not follow simple scaling with the dynamic exponent z, and that it involves an early time rise followed by late stage relaxation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Multiplicity and net-electric charge fluctuations in central Ar+Sc interactions at 13 A , 19 A , 30 A , 40 A , 75 A , and 150 A GeV/c beam momenta measured by NA61/SHINE at the CERN SPS

This paper presents results on multiplicity fluctuations of positively and negatively charged hadrons as well as net-electric charge fluctuations measured in central Ar+Sc interactions at beam momenta 13 A , 19 A , 30 A , 40 A , 75 A , and 150 A GeV/c. The fluctuation analysis is one of the tools to search for the predicted critical point of strongly interacting matter. Results are corrected for the experimental biases and quantified using cumulant ratios. In most instances, multiplicity and net-charge distributions appear narrower than the corresponding Poisson or Skellam distributions. Cumulant ratios are compared with the EPOS1.99 model predictions, which provide a qualitative description that aligns with observations for positively and negatively charged particles. The obtained results are also compared to earlier NA61/SHINE results from inelastic p+p interactions in the same analysis acceptance.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

MCS solutions for the TVA Watts Bar Unit 1 multi-physics depletion benchmark

The high-fidelity solution for exercises 1-3 of the recently developed TVA Watts Bar Unit 1 multi-physics and multi-cycle depletion benchmark using MCS was coupled with two different thermal-hydraulics (TH) codes: TH1D and COBRA-TF (CTF), and their solutions were compared. The solutions from MCS/CTF and MCS/TH1D for typical Pressurized Water Reactor (PWR) problems are quite close. And to evaluate MCS solutions for the benchmark, their results were also compared against measured data as well as publicly available high-fidelity solutions. The MCS criticality solutions at Hot Zero Power (HZP) deviate within 50 pcm against the reference solutions. While for the critical boron concentration (CBC) search calculations, the difference on the MCS calculated CBC is about 7 ppm, and the root-mean-squared (RMS) errors for the assembly power distribution and outlet coolant temperature are less than 0.5% and 1 Celsius degree respectively. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS2003

First Results of the Expedition to the Highest Lake on Earth: Studying a Martian Paleolake in Bolivia and the Survival Strategies Developed by Living Organisms

Between October 16th and November 9th 2002, the first NASA Ames DDF Licancabur multidisciplinary expedition initiated the investigation of the biology and environment for life in the highest lake on Earth located at the summit of the Licancabur volcano (6017 m/20,056 ft) at the boundary of Chile and Bolivia. The low oxygen, low atmospheric pressure, high-UV radiation, average temperature, volcano-tectonic and hydrothermal environment make the site a close analog to Martian paleolakes 3.5 billion years ago. The overall goal of the project is to understand through a series of high altitude scientific expeditions what strategies life is using to defend itself against killer-level UV radiation and environmental extreme conditions at this altitude. Several other lakes are located at 4300 m at the foot of the Licancabur volcano (hereafter named laguna Blanca and Laguna Verde). They were also investigated using identical experiments and methods as for the summit lake in order to compare the results and better understand the evolution of survival strategies at transitioning elevations. The lagunas are geothermally heated and many springs provide water at various temperatures. Sources of heat are also suspected for the summit lake as its surface water temperature was measured during the successful ascent at +6 C in a -9 C ambient crater environment (with a wind chill factor of -25 C with a wind blowing almost constantly). Results of this project are expected to provide critical keys to help searching and identifying potential sites for life (extant/extinct) on Mars and developing instruments, experiments and technologies for future missions.

Cabrol, N. A.↗
DOE OSTI2021

FAIR Interfaces for Geospatial Scientific Data Searches

Several factors must be considered in designing a highly accurate, reliable, scalable, and user-friendly geospatial data search interfaces. This paper examines four critical questions that ought to be considered during design phase: (1) Is the search interface or API that provides the search capability useable by both humans and machines? (2) Are the results consistent and reliable? (3) Is the output response format free to use, community-defined, and non-propriety? (4) Does the API clearly state the usage clauses? This paper discusses how certain data repositories at the US Department of Energy's Oak Ridge National Laboratory apply FAIR data principles to enable geospatial searches and address the above-mentioned questions.

Devarakonda, Ranjeet↗