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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Beta-Delayed Neutron Emission of 𝑁=84 132Cd

Using the time-of-flight technique, we measured the beta-delayed neutron emission of 132 Cd . From our large-scale shell model (LSSM) calculation using the N3⁢LO interaction [, Phys. Rev. Lett. 131, 022501 (2023)], we suggest the decay is dominated by the transformation of a neutron in the 𝑔7/2 orbital, deep below the Fermi surface, into a proton in the 𝑔9/2 orbital. We compare the beta-decay half-lives and neutron branching ratios of nuclei with 𝑍<50 and 𝑁 ≥82 obtained with our LSSM with those of leading “global” models such as finite-range droplet model (FRDM). Our calculations match known half-lives and neutron branching ratios well and suggest that current leading models overestimate the yet-to-be-measured half-lives. Our model, backed by the 132 Cd decay data presented here, offers robust predictive power for nuclei of astrophysical interest such as 𝑟-process waiting points.

Madurga, M [Department of Physics and Astronomy, U↗
DOE OSTI2022

Volt-VAR Optimization in Distribution Networks Using Twin Delayed Deep Reinforcement Learning

Modern distribution grids are undergoing new challenges due to the stochastic nature of distributed energy resources (DERs). High penetration of DERs has a significant impact on Volt-VAR profile and system power losses. This work proposes a deep reinforcement learning (DRL)-based Volt-VAR optimization approach for improving voltage profile and reducing system power loss under high penetration of distributed energy resources, such as battery energy storage and solar photovoltaic units in distribution grids. The twin delayed deep deterministic policy gradient (TD3) method-based DRL agent is proposed to configure optimal set-points of reactive power outputs of fast responding smart inverters. The agent schedules the reactive power of inverters according to their physical capabilities, such as minimum allowed power factor, e.g., 0.9 leading/lagging. The reward function of the proposed DRL scheme is designed carefully to ensure a proper voltage profile of the grids with effective scheduling of reactive power outputs from inverters. The performance of the proposed model is verified on modified IEEE 34- and 123-bus systems and compared with base case with no reactive supply by inverters, and local droop Volt-VAR control approach. The results show that the proposed method performs better than the local droop control and deep deterministic policy gradient (DDPG)-based DRL method for reducing voltage fluctuation and minimizing power loss.

Hossain, Rakib↗
DOE OSTI2024

A Perspective on the Impact of Group Delay Dispersion in Future Terahertz Wireless Systems

This article discusses the challenges and opportunities of managing group delay dispersion (GDD), and its relation to the performance standards of future sixth-generation (6G) wireless communication systems utilizing terahertz frequency waves. The unique susceptibilities of 6G systems to GDD are described, along with a quantitative description of the sources of GDD, including multipath, rough surface scattering, intelligent reflecting surfaces, and propagation through the atmosphere. An experimental case-study is presented that confirms previous models quantifying the impact of atmospheric GDD. Several GDD manipulation strategies are presented, illustrating their hindered effectiveness in the 6G context. Conversely, some benefits of leveraging GDD to enhance 6G systems, such as improved security and simplified hardware, are also discussed. Finally, a perspective on using photonic GDD control devices is provided, revealing quantitative benefits that may unburden existing equalization schemes. Here, the article argues that GDD will uniquely and significantly impact some 6G systems, but that its careful consideration along with new mitigation strategies, including photonic devices, will help optimize system performance. The conclusion provides a perspective to guide future research in this area.

Strecker, Karl↗
DOE OSTI2025

Model-Free Control of Grid-Interactive Efficient Buildings Under Communication Time Delays

Grid-interactive efficient buildings (GEBs) have recently been used to enhance the reliability and stability of the electric grid through demand response (DR) programs. However, most existing DR control strategies require accurate modeling of the various building thermostatically controlled loads (TCLs) and are computationally expensive. To address these challenges, a model-free control (MFC)-based strategy has recently been introduced for coordinating and controlling GEBs. MFC is a data-enabled control strategy that is computationally efficient and does not require the analytical models of the various building equipment. In this paper, we numerically investigate the impact of communication time delays on the performance of MFC in maintaining the TCLs' temperatures within the desired comfort levels while meeting the assigned power allocation constraint.

Telsang, Bhagyashri [University of Tennessee, Knox↗
DOE OSTI2023

Attosecond photoionization delays in the vicinity of molecular Feshbach resonances

Temporal delays extracted from photoionization phases are currently determined with attosecond resolution by using interferometric methods. Such methods require special care when photoionization occurs near Feshbach resonances due to the interference between direct ionization and autoionization. Although theory can accurately handle these interferences in atoms, in molecules, it has to face an additional, so far insurmountable problem: Autoionization is slow, and nuclei move substantially while it happens, i.e., electronic and nuclear motions are coupled. Here, we present a theoretical framework to account for this effect and apply it to evaluate time-resolved and vibrationally resolved photoelectron spectra and photoionization phases of N 2 irradiated by a combination of an extreme ultraviolet (XUV) attosecond pulse train and an infrared pulse. We show that Feshbach resonances lead to unusual non–Franck-Condon vibrational progressions and to ionization phases that strongly vary with photoelectron energy irrespective of the vibrational state of the remaining molecular cation.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2025

Correlation-driven attosecond photoemission delay in the plasmonic excitation of C60 fullerene

Extreme light confinement in plasmonic nanosystems enables novel applications in photonics, sensor technology, energy harvesting, biology, and quantum information processing. Fullerenes represent an extreme case for nanoplasmonics: they are sub-nanometer carbon- based molecules showing high-energy and ultrabroad plasmon resonances, however the fundamental mechanisms driving the plasmonic response and the corresponding collective electron dynamics are still elusive. Here, we uncover the dominant role of electron correlations in the dynamics of the giant plasmon resonance (GPR) of the sub-nanometer system C60 by employing attosecond photoemission chronoscopy. We find a characteristic photoemission delay of up to about 300 attoseconds that is purely induced by coherent large-scale electron correlations in the plasmonic potential. These results provide novel insights into the nature of the plasmon resonances in sub-nanometer systems and open new perspectives for advancing nanoplasmonic applications.

Biswas, Shubhadeep [SLAC National Accelerator Labo↗
DOE OSTI2020

In-Device Delay: Introduction to Obscurant Physcial Protection System

The Office of Radiological Security (ORS) In-Device Delay (IDD) program has undertaken a project to research and develop a novel protection system for industrial irradiators that contain high-activity Co-60 sources. Based on adversary testing conducted by ORS, it is was determined that to successfully accomplish the theft of the target material, the adversary will require visual contact of the sources and source rack located at the bottom of the pool. Therefore, if a means of obscuring or visually hiding the sources in the pool can be achieved (while adhering to facility operations, safety, and regulatory requirements), then illicit source theft will be significantly hindered. This project aims to develop a low-cost, non-propriety obscurant that, when an adversary action is detected, the obscurant will be deployed into the pool quickly, rendering visual observation of the source problematic; however, this obscurant will not otherwise disturb the sources, source rack, and filtration system. The obscurant will remain in the pool until removed by another process.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2020

Two Delayed Critical 15-Inch-Diameter Interacting Enriched (93.14) Uranium Metal Cylinders without Moderator and Reflector

This report documents very accurately the configuration and the materials for experiments with two unmoderated, unreflected, interacting, coaxial, highly enriched, 15-in.-diameter, uranium metal cylinders performed at the Oak Ridge Critical Experiments Facility (ORCEF) in May to Aug 1963 and described in logbook E-19 and E -20 associated with experiments in the East cell of ORCEF. Measurements were also performed in April and May of 1965 and described in logbooks E-22 and E-23 The information is sufficiently accurate that it can be used as the basis for preparation of benchmarks for International Criticality Safety Benchmark Program (ICSBEP) at Idaho National laboratory. The thickness of the cylinders was varied and the spacing between them was adjusted to achieve a delayed critical configuration. The average enrichment of the uranium metal was 94.14 wt. % 235 U. The heights of the 15-in.-diameter, equal-height cylinders varied from 1-5/8 to 3.0-inches. All interacting cylinders were assembled coaxially with their flat faces parallel and their combined masses varied between 182 and 325 kilograms of HEU metal. The data from these 12 experiments described would be acceptable for use as criticality safety benchmark experiments for the ICSBEP and EURATOM’s Nuclear Energy Agency nuclear criticality safety benchmark program, once the uncertainty analysis is completed. Based on previous ICSBEP benchmarks with this enriched uranium metal at ORCEF, it is expected that the uncertainties in k eff could be as low as ± 0.0002.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Three Delayed Critical 15-Inch-Diameter Interacting Enriched (93.14) Uranium Metal Cylinders Without Moderator and Reflector

This report documents very accurately the configuration and the materials for experiments with three unmoderated, unreflected, interacting, coaxial, highly enriched, 15-in.-diameter, uranium metal cylinders performed at the Oak Ridge Critical Experiments Facility (ORCEF) in August and September 1963 and described in logbook E 20 associated with experiments in the East cell of ORCEF. The information is sufficiently accurate that it can be used as the basis for preparation of benchmarks for International Criticality Safety Benchmark Program (ICSBEP) at Idaho National laboratory. The thickness of the cylinders was varied and the spacing between them was adjusted to achieve a delayed critical configuration. The average enrichment of the uranium metal was 94.14 wt. % 235U. The heights of the 15-in.-diameter, equal-height cylinders varied from 1-1/8to 2.00 inches. All interacting cylinders were assembled coaxially with their flat faces parallel and their combined masses varied between 182 and 325 kilograms of HEU metal. The data from these six experiments described are judged to be acceptable for use as criticality safety benchmark experiments for the ICSBEP and EURATOM’s Nuclear Energy Agency nuclear criticality safety benchmark program, once the uncertainty analysis is completed. Based on previous ICSBEP benchmarks with this enriched uranium metal at ORCEF, it is expected that the uncertainties in measured keff could be as low as ± 0.0002.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Characterization of the Sub-mm Delay Plates for the IOTA Optical-Stochastic-Cooling Experiment

This note describes the methods used to measure the thickness profile of the glass plates used in the optical-delay line of the Optical Stochastic Cooling (OSC) experiment at the Fermilab’s IOTA ring. The plates have a nominal thickness of 250 μm and the measurement was performed to verify the nominal thickness and determine its variation over the entire plate surface. All the available plates were characterized and the impact of the thickness variation on the radiation wave front was found to be negligible using wave-optics simulation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Summary of GAIN BWR Off-Gas Study: Effect of Charcoal on Kr and Xe Delay

This is a summary of a more extensive report, written in collaboration with the GE-Hitachi BWR Owner's Group, detailing a study of BWR off-gas treatment. The study determined that aged charcoal continues to be effective for the delay of Kr and Xe through BWR off-gas treatment systems. It demonstrates the over-sized nature of existing charcoal beds, and highlights potential areas of improvement.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2023

Data-driven time-scale separation of ODE right-hand sides using dynamic mode decomposition and time delay embedding

Multi-physics simulation often involves multiple different scales. The ARKODE ODE solver package in the SUNDIALS library addresses multi-scale problems with a multi-rate time-integrator that can work with a right-hand side that has fast scale and slow scale components. In this report, we use dynamic mode decomposition and time delay embedding to extract the fast and slow components of the right-hand sides of a simple ODE from data. We then use the extracted components to solve the ODE with ARKODE. Finally, to move towards a real-world use case, we attempt to extract fast and slow scale dynamics from synthetic seismic modeling data.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

One-Turn Delay Feedback (OTFB) Implementation for the EIC

This paper discusses the implementation of the One-Turn Delay Feedback (OTFB) for the Electron-Ion Collider (EIC). The theory of the OTFB is well documented, therefore, this paper will mainly discuss the details of the implementation. After a short introduction, the paper will discuss the building-blocks of the OTFB, simulation testing of the OTFB, and finally hardware validation of the OTFB.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Demonstration of Control of Laser-Plasma Instabilities in the Laboratory Using STUD Pulses (Spike Trains of Uneven Duration and Delay)

The success of laser Driven Inertial Fusion Technology (LaDrIFT) hinges on controlling laser-plasma instabilities (LPI) for effective and non-deleterious energy coupling, together with the control of implosion hydrodynamic instabilities (IHI) for target integrity. Conventional approaches ignore LPI and focus on IHI. LPI control suggests the use of low intensities, short wavelengths, and thus the slow implosions of thinner shells, while IHI control calls for thicker shells, fast implosions and thus at higher laser intensities and ablation pressures. These contradicting requirements severely restrict LaDrIFT design space, flexibility and scalability. This program demonstrates, with theoretical designs and their preliminary experimental realizations, that STUD pulses (Spike Trains of Uneven Duration and Delay) can control LPI in high-energy-density (HED) laser-created plasmas and explore this physics for the first time with high repetition (rep) rate lasers.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Batch Measurement Extremum Seeking Control of Distributed Energy Resources to Account for Communication Delays and Information Loss

Distributed Energy Resources (DER) have great potential to enhance the operation of electric power distribution systems. Previously, we explored the use of 2 Dimensional Extremum Seeking (2D-ES) control algorithms to enable model-free optimal control of DER to provide grid services to both the distribution and transmissions systems. Motivated by preliminary deployments of DER managed by 2D-ES algorithms in hardware-in-the-loop tests and in operational distribution grids, in this work, we extend the control scheme to accommodate communication delays and information loss. We propose a modification to the 2D-ES scheme to allow for the processing of batches of possibly noncontiguous objective function measurements at unknown and possibly uneven intervals. We provide a proof of the convergence of the batch 2D-ES (2D-BES) scheme when optimizing a generic convex objective function, as well as simulation results that demonstrate the suitability of the approach for substation active and reactive power target tracking.

Sankur, Michael↗
DOE OSTI2020

Autoignition delay times measurements of linear unsaturated jet fuel compounds inside a shock tube

Autoignition delay times measurements and CO time histories were studied for 2-pentene, a hydrocarbon in aviation fuel and an important species in the development of aviation fuel surrogates. Three mechanisms from the literature were compared against the measured data, and a sensitivity analysis for CO was performed for all mechanisms. Shock tube experiments were performed between 1246 K – 1372 K and 8.8 atm – 9.3 atm at an equivalence ratio of 1, a fuel loading of 0.25% was used and was balanced in oxygen and argon. Discrepancies between the available literature mechanisms exist, the measured data herein is essential for validation of these mechanisms and the reduction of validated mechanisms for coupling into CFD.

09 BIOMASS FUELS↗