Statistical Methods for Selecting a Pair of Differential and Integral Experiments that Reduce Uncertainties in Intermediate-Energy Nuclear Data [Slides]
Abstract not provided.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
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Machine learning selection of differential and integral experiments to optimally reduce nuclear data uncertainties [Slides]
Abstract not provided.
Nuclear Criticality Safety Program (NCSP)↗
Selection of a Pair of Experiments to Optimally Reduce Uncertainty in Targeted Nuclear Data
We propose a novel process to select a pair of differential and integral experiments that best reduce uncertainties in targeted 239 Pu nuclear data while compressing the current nuclear data pipeline from 20 to 3 years. 239 Pu nuclear data are poorly understood for neutrons in the intermediate energy range due to sparsity and uncertainty in historical experiments. New experiments targeting this range will enable better understanding of these nuclear data, but choosing the ideal experiments to conduct is challenging. Beginning with a prior distribution represented by samples of nuclear data generated from theory, generalized least squares adjustments are made to incorporate data from historical experiments. To quantify potential uncertainty reduction obtainable from a pair of candidate experiments, we compute the D-optimality criterion of the posterior covariance of intermediate energy range nuclear data compared to the equivalent covariance after additional adjustment to the pair of candidate experiments. Repeating the process for each of many candidate pairs facilitates the final selection. Results support 63 Cu total cross section measurements for differential experiments and alumina and alumina/graphite configurations for integral experiments. This analysis enables choosing differential and integral experiments to be executed concurrently while shortening decision times relative to the current nuclear data pipeline.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Differential Drag Demonstration: A Post-Mission Experiment with the EO-1 Spacecraft
Differential drag is a technique for altering the semi-major axis, velocity, and along-track position of a spacecraft in low Earth orbit. It involves varying the spacecrafts cross-sectional area relative to its velocity direction by temporarily changing attitude and solar array angles, thus varying the amount of atmospheric drag on the spacecraft. The technique has recently been proposed and used by at least three satellite systems for initial separation of constellation spacecraft after launch, stationkeeping during the mission, and potentially for conjunction avoidance. Similarly, differential drag has been proposed as a control strategy for rendezvous, removing the need for active propulsion. In theory, some operational missions that lack propulsion capability could use this approach for conjunction avoidance, though options are typically constrained for spacecraft that are already in orbit. Shortly before the spacecraft was decommissioned, an experiment was performed using NASAs EO-1 spacecraft in order to demonstrate differential drag on an operational spacecraft in orbit, and discover some of the effects differential drag might manifest. EO-1 was not designed to maintain off-nominal orientations for long periods, and as a result the team experienced unanticipated challenges during the experiment. This paper will discuss operations limitations identified before the experiment, as well as those discovered during the experiment. The effective displacement that resulted from increasing the drag area for 39 hours will be compared to predictions as well as the expected position if the spacecraft maintained nominal operations. A hypothetical scenario will also be examined, studying the relative risks of maintaining an operational spacecraft bus in order to maintain the near-maximum drag area orientation and hasten reentry.
differential drag↗
Materials Compatibility in High Test Hydrogen Peroxide
Previous ratings of the compatibility of high test hydrogen peroxide (HTP) with materials are not adequate for current needs. The goal of this work was to develop a new scheme of evaluation of compatibility of HTP with various materials. Procedures were developed to enrich commercially available hydrogen peroxide to 90% concentration and to assay the product. Reactivity testing, accelerated aging of materials and calorimetry studies were done on HTP with representative metallic and non-metallic materials. It was found that accelerated aging followed by concentration determination using refractive index effectively discriminated between different Class 2 metallic materials. Preliminary experiments using Differential Scanning Calorimetry (DSC) suggest that a calorimetry experiment is the most sensitive means to assay the compatibility of HTP with materials.
Gostowski, Rudy↗
Differential Drag Demonstration: A Post-Mission Experiment with the EO-1 Spacecraft
Differential drag is a technique for altering the semimajor axis, velocity, and along-track position of a spacecraft in low Earth orbit. It involves varying the spacecraft's cross-sectional area relative to its velocity direction by temporarily changing attitude and solar array angles, thus varying the amount of atmospheric drag on the spacecraft. The technique has recently been proposed and used by at least three satellite systems for initial separation of constellation spacecraft after launch, stationkeeping during the mission, and potentially for conjunction avoidance. Similarly, differential drag has been proposed as a control strategy for rendezvous, removing the need for active propulsion. In theory, some operational missions that lack propulsion capability could use this approach for conjunction avoidance, though options are typically constrained for spacecraft that are already in orbit. Shortly before the spacecraft was decommissioned, an experiment was performed using NASA's EO-1 spacecraft in order to demonstrate differential drag on an operational spacecraft in orbit, and discover some of the effects differential drag might manifest. EO-1 was not designed to maintain off-nominal orientations for long periods, and as a result the team experienced unanticipated challenges during the experiment. This paper will discuss operations limitations identified before the experiment, as well as those discovered during the experiment. The effective displacement that resulted from increasing the drag area for 39 hours will be compared to predictions as well as the expected position if the spacecraft maintained nominal operations. A hypothetical scenario will also be examined, studying the relative risks of maintaining an operational spacecraft bus in order to maintain the near-maximum drag area orientation and hasten reentry.
orbital lifetim↗
Fast Neutron Evaluations for Advanced Lead Systems [Slides]
This presentation touches on fast neutron evaluations for advanced lead systems. This lecture covers project goals to evaluate lead (Pb) isotopes with a focus on improving predictive capabilities of fast systems. Additionally, the project sets out to benchmark available critical and shielding experiments with sensitivity to Pb and utilize RPI Quasi-Differential Scattering experiment for scattering reactions. This project will perform Resolved Resonance Region (RRR) and fast region evaluations for natural Pb isotopes with differential data on EXchange FORmat for experimental numerical nuclear reaction data (EXFOR) and ultimately will submit evaluations to the ENDF/B-VIII.1 library.
07 ISOTOPE AND RADIATION SOURCES↗
Importance of Higher Fidelity Model Geometries during Optimization of Critical Experiments
PARADIGM, PARallel Approach of Differential and InteGral Measurements, is a cross-collaborative effort at Los Alamos National Laboratory between nuclear data theorists, differential and integral experimenters, as well as machine learning statisticians to tackle uncertainties in the intermediate region of 239 Pu. In essence, the idea behind PARADIGM is to remove the linear conceptualization of the nuclear data pipeline, shown in Figure 1, and replace it with a far more parallelized approach. The novel approach leverages machine learning to guide which differential measurements and integral experiments will result in the largest decrease in uncertain ties for a nuclide reaction pair in a given energy range. The concept builds off earlier work, EUCLID, which focused on the fast region of 239 Pu. The practical benefit of having evaluation, differential measurement, and integral experiment personnel in collaboration with machine learning is to represent the entire nuclear data in one snapshot. This enable large reduction in the time to deliver improved nuclear data, which using the PARADIGM approach could be done in 3 years. A general outline of PARADIGM and specific topics are available in other papers. The discussion here will pertain directly to the integral experiment design. More specifically, the process of taking a rough design and transforming it into a finalized neutronic model will be discussed.
97 MATHEMATICS AND COMPUTING↗
Accurate Measurement of Heat Capacity by Differential Scanning Calorimetry
Experience with high quality heat capacity measurement by differential scanning calorimetry is summarized and illustrated, pointing out three major causes of error: (1) incompatible thermal histories of the sample, reference and blank runs; (2) unstable initial and final isotherms; (3) incompatible differences between initial and final isotherm amplitudes for sample, reference and blank runs. Considering these problems, it is shown for the case of polyoxymethylene that accuracies in heat capacity of 0.1 percent may be possible.
Source record↗
Meteorological factors in Earth-satellite propagation
Using the COMSTAR D/4 28.56 GHz beacon as a source, a differential gain experiment was performed by connecting a 5-meter paraboloidal antenna and a 0.6-meter paraboloidal antenna alternately to the same receiver. Substantial differential gain changes were observed during some, but not all, rain events. A site-diversity experiment was implemented which consists of two 28.56 GHz radiometers separated by 9 km. The look-angle corresponds to that of the D/4 beacon, and data were obtained with one radiometer during several weeks of concurrent beacon operation to verify the system calibration. A theoretical study of the effect of scattering from a nonuniform rain distribution along the path is under way to aid in interpreting the results of this experiment. An improved empirical site diversity-gain model was derived from data in the literature relating to 34 diversity experiments. Work on the experiment control and data acquisition system is continuing with a view toward future experiments.
Levis, C. A.↗
A small core in Vesta inferred from Dawn’s observations
Vesta’s large-scale interior structure had previously been constrained primarily using the gravity and shape data from the Dawn mission. However, these data alone still allow a wide range of possibilities for the differentiation state of the body. The moment of inertia is arguably the most diagnostic parameter related to the radial density distribution of a planetary body, making it crucial for assessing the body’s state of internal differentiation. Determining the moment of inertia requires additional measurements of the amplitudes of small rotational motions, such as precession and nutation. Here we report an updated estimate of the moment of inertia of Vesta inferred from Dawn’s Doppler tracking via the Deep Space Network and onboard imaging data. The recovered value for Vesta’s normalized polar moment of inertia is $\overline{C}$/MR 2 = 0.4208 ± 0.0047 (where M is the mass of Vesta and R is the reference radius), which is only 6.6% lower than the homogeneous value of 0.4505. This value, combined with the gravity field and global shape, suggests that Vesta’s interior has limited density stratification beneath its howardite–eucrite–diogenite-dominated crust. We propose two possible origin scenarios that are consistent with the observed constraints. In the first scenario, Vesta’s interior did not undergo full differentiation due to late accretion. In the second scenario, Vesta originated as an impact remnant of a larger differentiated body re-accreted with non-chondritic bulk composition produced from a catastrophic impact. Vesta did not experience complete differentiation in either scenario, suggesting that its current state reflects a complex interplay between its accretion timing, thermal evolution, redistribution of 26 Al bearing melt and/or impact processes.
CNEOS 2014-01-08 bolide↗
Weak structure functions in $\nu_l-N$ and $\nu_l-A$ scattering with nonperturbative and higher order perturbative QCD effects
We study the effect of various perturbative and nonperturbative QCD corrections on the free nucleon structure functions [FiNWI(x,Q2);i=1–3] and their implications in the determination of nuclear structure functions. The evaluation of the nucleon structure functions has been performed by using the MMHT 2014 parton distribution functions (PDFs) parametrization, and the target mass correction (TMC) and higher twist (HT) effects are incorporated following the works of Schienbein et al. and Dasgupta et al., respectively. These nucleon structure functions are taken as input in the determination of nuclear structure functions. The numerical calculations for the νl/ν¯l-A deep inelastic scattering (DIS) process have been performed by incorporating the nuclear medium effects like Fermi motion, binding energy, nucleon correlations, mesonic contributions, shadowing, and antishadowing in several nuclear targets such as carbon, polystyrene scintillator, iron, and lead, which are being used in MINERνA, and in argon nuclei, which is relevant for the ArgoNeuT and DUNE experiments. The differential scattering cross sections d2σAWIdxdy and (dσAWIdx/dσCHWIdx) have also been studied in the kinematic region of the MINERνA experiment. The theoretical results are compared with the recent experimental data of MINERνA and the earlier data of the NuTeV, CCFR, CDHSW, and CHORUS Collaborations. Moreover, a comparative analysis of the present results for the ratio (dσAWIdx/dσCHWIdx), and the results from the Monte Carlo (MC) generator GENIE and other phenomenological models of Bodek and Yang, and Cloet et al., has been performed in the context of the MINERνA experiment. The predictions have also been made for the ν¯l-A cross section relevant for the MINERνA experiment.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Proposed Methodology for Evaluating and Validating TSLs [Slides]
This presentation begins by providing an overview of the research and discusses recent efforts in validating thermal neutron scattering cross sections, including differential cross section measurements at ORNL for evaluation and validation, total cross section measurements at RPI, pulsed-neutron die-away experiments at LLNL, and integral criticality experiments by LLNL. The presentation also proposes a methodology not only for validating thermal scattering files that utilizes all available experimental data, but also for evaluating new libraries as demonstrated on polystyrene. In conclusion, polystyrene evaluation was conducted using multiple experiments, including differential and integral. The proposed methodology has been shown to improve neutron transport and files have been submitted to NNDC for inclusion in ENDF/B-VIII.1 release. MCT-012 & PCM-002 has been relatively insensitive to changes in $\mathcal{S}(α,β)$. The research found that differences in differential results don’t always propagate to differences in integral results, hence why evaluation of differential data important. Future work on the project is also discussed.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Randomized measurement protocols for lattice gauge theories
Randomized measurement protocols, including classical shadows, entanglement tomography, and randomized benchmarking are powerful techniques to estimate observables, perform state tomography, or extract the entanglement properties of quantum states. While unraveling the intricate structure of quantum states is generally difficult and resource-intensive, quantum systems in nature are often tightly constrained by symmetries. Furthermore, this can be leveraged by the symmetry-conscious randomized measurement schemes we propose, yielding clear advantages over symmetry-blind randomization such as reducing measurement costs, enabling symmetry-based error mitigation in experiments, allowing differentiated measurement of (lattice) gauge theory entanglement structure, and, potentially, the verification of topologically ordered states in existing and near-term experiments. Crucially, unlike symmetry-blind randomized measurement protocols, these latter tasks can be performed without relearning symmetries via full reconstruction of the density matrix.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Angular distribution for electron excitation of the 4(2)S yields 4(2)P transition in Zn II - Comparison of experiment and theory
Differential electron-scattering cross sections for inelastic excitation of an ion have been measured for the first time. Experiments were carried out in a cross electron-ion beam geometry for the 4(2)S yields 4(2)P transition in Zn II at 75 eV. In addition, differential cross sections were calculated at energies between 15 and 100 eV in a five-state close-coupling approximation in which 4s, 4p, 3d(9)4s(2), 5s, and 4 d states were included. Agreement in shape between theory and experiment at 75 eV is excellent.
Chutjian, A.↗
Differential phase shift of partially reflected radio waves.
The addition of phase difference measurements to differential absorption experiments is shown to be both feasible and desirable. The phase information can provide a more sensitive measurement of electron density above about 75 km. The differential phase shift is only weakly dependent on collision frequency in this range, and so an accurate collision frequency profile is not a prerequisite. The differential phase shift and differential absorption measurements taken together can provide both electron density and collision frequency data from about 70 to 90 km.
Connolly, D. J.↗
Detached Bridgman Growth of Germanium and Germanium-Silicon Alloy Crystals
Earth based experiments on the science of detached crystal growth are being conducted on germanium and germanium-silicon alloys (2 at% Si average composition) in preparation for a series of experiments aboard the International Space Station (ISS). The purpose of the microgravity experiments includes differentiating among proposed mechanisms contributing to detachment, and confirming or refining our understanding of the detachment mechanism. Because large contact angle are critical to detachment, sessile drop measurements were used to determine the contact angles as a function of temperature and composition for a large number of substrates made of potential ampoule materials. Growth experiments have used pyrolytic boron nitride (pBN) and fused silica ampoules with the majority of the detached results occurring predictably in the pBN. The contact angles were 173 deg (Ge) and 165 deg (GeSi) for pBN. For fused silica, the contact angle decreases from 150 deg to an equilibrium value of 117 deg (Ge) or from 129 deg to an equilibrium value of 100 deg (GeSi) over the duration of the experiment. The nature and extent of detachment is determined by using profilometry in conjunction with optical and electron microscopy. The stability of detachment has been analyzed, and an empirical model for the conditions necessary to achieve sufficient stability to maintain detached growth for extended periods has been developed. Results in this presentation will show that we have established the effects on detachment of ampoule material, pressure difference above and below the melt, and silicon concentration; samples that are nearly completely detached can be grown repeatedly in pBN.
Szofran, F. R.↗
Numerical weather prediction in low latitudes
Based on the results of a number of numerical prediction experiments, the differential heating between land and ocean is an important and critical factor for investigation of phenomenon such as the onset of monsoons over the Indian subcontinent. The pre-onset period during the month of May shows a rather persistent flow field in the monsoon region. At low levels the circulation exhibits anticyclonic excursions over the Arabian Sea, flowing essentially parallel to the west coast of India from the north. Over the Indian subcontinent the major feature is a shallow heat low over northern India. As the heat sources commence a rapid northwestward movement toward the southern edge of the Tibetan Plateau, an interesting configuration of the large-scale divergent circulation occurs. A favorable configuration for a rapid exchange of energy from the divergent to the rotational kinetic energy develops. Strong low level monsoonal circulations evolve, attendant with that the onset of monsoon rains occurs. In order to test this observational sequence, a series of short-range numerical prediction experiments were initiated to define the initial heat sources.
Krishnamurti, T. N.↗