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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 OSTI2024

Dopant, coating, and grating effects in silica optical fibers under extreme neutron irradiation

Radiation effects on fiber Bragg gratings (FBGs) have been studied but data gaps related to the effects of displacement damage resulting from high fast neutron fluence remain. In this work, Type-I and Type-II FBGs inscribed in optical fibers with various core dopants (Ge and F) and fiber coatings (acrylate, polyimide) were monitored in situ during 75 days of neutron irradiation to a peak fast (>0.1 MeV) neutron fluence of 3 X 10 21 n fast /cm 2 . Further, the reflected intensity of the Type-I FBGs inscribed in a Ge-doped core fiber decreased by > 30 dB within 7 h of irradiation (10 19 n fast /cm 2 ), whereas Type-II FBGs inscribed in a pure silica core fiber eventually approached >40 dB attenuation after accumulating a fast neutron fluence on the order of 10 20 n fast /cm 2 . Type-II FBGs inscribed in F-doped core fiber improved stability: the attenuation approached an equilibrium value in the range of 10 to 20 dB.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Neutron elastic scattering on calcium isotopes from chiral nuclear optical potentials

We formulate microscopic neutron-nucleus optical potentials from many-body perturbation theory based on chiral two- and three-body forces. The neutron self-energy is first calculated in homogeneous matter to second order in perturbation theory, which gives the central real and imaginary terms of the optical potential. Here, the real spin-orbit term is calculated separately from the density matrix expansion using the same chiral interaction as in the self-energy. Finally, the full neutron-nucleus optical potential is derived within the improved local density approximation utilizing mean-field models consistent with the chiral nuclear force employed. We compare the results of the microscopic calculations to phenomenological models and experimental data up to projectile energies of E = 200 MeV. Experimental elastic differential scattering cross sections and vector analyzing powers are generally well reproduced by the chiral optical potential, but we find that total cross sections are overestimated at high energies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

A science-driven approach to optimize the design for a biological small-angle neutron scattering instrument

Biological small-angle neutron scattering (SANS) instruments facilitate critical analysis of the structure and dynamics of complex biological systems. However, with the growth of experimental demands and the advances in optical systems design, a new neutron optical concept is necessary to overcome the limitations of current instruments. This work presents an approach to include experimental objectives ( i.e. the science to be supported by a specific neutron scattering instrument) in the optimization of the neutron optical concept. The approach for a proposed SANS instrument at the Second Target Station of the Spallation Neutron Source at Oak Ridge National Laboratory, USA, is presented here. Further, the instrument is simulated with the McStas software package. The optimization process is driven by an evolutionary algorithm using McStas output data, which are processed to calculate an objective function designed to quantify the expected performance of the simulated neutron optical configuration for the intended purpose. Each McStas simulation covers the complete instrument, from source to detector, including realistic sample scattering functions. This approach effectively navigates a high-dimensional parameter space that is otherwise intractable; it allows the design of next-generation SANS instruments to address specific scientific cases and has the potential to increase instrument performance compared with traditional design approaches.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Enhanced backscatter and unsaturated blue wavelength shifts in F-doped fused silica optical fibers exposed to extreme neutron radiation damage

Amorphous fused silica (a-SiO 2 ) optical fibers, with and without inscribed Bragg gratings, were interrogated using infrared (~1550 nm) optical backscatter reflectometry during ~25 days of intense neutron irradiation to a fast (energy > 0.1 MeV) neutron fluence of ~10 21 n/cm 2 , or ~1.5 atomic displacements per atom. The reflected light amplitudes in Ge-doped core telecommunications fiber dropped below detection limits (>15 dB attenuation) within 3 days of irradiation (~10 20 fast n/cm 2 ). Here, amplitudes from a pure silica core, F-doped silica cladding fiber reached equilibrium levels ~1.5–2 dB higher than pre-irradiation values, whereas Bragg gratings inscribed in the same fiber using a femtosecond laser (point-by-point method) suffered > 45 dB attenuation. Blue wavelength shifts were initially consistent with previous radiation-induced compaction models but increased linearly with increasing neutron fluence (no evidence of saturation) beyond 10 20 n/cm 2 and exceeded 0.6%, which corresponds to >1,000 °C drift if used to measure temperature changes.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Incident beam optics optimization for the single crystal neutron diffractometer Pioneer with a polarized beam option

Pioneer, a next-generation single-crystal neutron diffractometer, is under development for Oak Ridge National Laboratory’s Second Target Station. Designed to address a wide range of scientific questions, Pioneer will deliver homogeneous neutron beams with customizable size and divergence and provide a polarized beam option. This article introduces its incident beam optics, highlighting the optimization methodology and the simulated performance. Pioneer will utilize a modified elliptical-straight guide for neutron transport and deploy slit packages and insertable apertures to control beam size and divergence. The optimized guide geometry matches the optimal-and-full-sample-illumination condition, and the beam control system effectively filters out unwanted neutrons while preserving the desired ones. In addition, we have found that polygon-approximated guides provide satisfactory transport efficiency and beam homogeneity, eliminating the need for truly curved guides. Further, to enhance neutronics performance and reduce cost, the coatings of supermirror elements are individually optimized to the lowest half-integer m-values that are sufficient to deliver the desired neutrons. After evaluating polarizing V-cavities and 3 He spin filters over the default polarized wavelength band of 1.2–5.5 Å, we selected a translatable multichannel polarizing V-cavity as the incident beam polarizer. Strategically placed at a location where the beam divergence is low and a large in-guide gap has negligible impact on transport efficiency, the optimized V-cavity achieves an average P 2 T of ~35%.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Design of the ion-optics for the MRSt neutron spectrometer at the National Ignition Facility (NIF)

A new Magnetic Recoil Spectrometer (MRSt) is designed to provide time-resolved measurements of the energy spectrum of neutrons emanating from an inertial confinement fusion implosion at the National Ignition Facility. At present, time integrated parameters are being measured using the existing magnet recoil and neutron time-of-flight spectrometers. The capability of high energy resolution of 2 keV and the extension to high time resolution of about 20 ps are expected to improve our understanding of conditions required for successful fusion experiments. The layout, ion-optics, and specifications of the MRSt will be presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2026

3⁢𝑄 magnetic order with spatially alternating spin scalar chirality in overdoped C⁢o 0.336⁢ Ta⁢S 2

C⁢o 𝑥 ⁢Ta⁢S 2 (𝑥≈1/3) exhibits a spontaneous Hall effect from spin texture in antiferromagnets, with a tetrahedral triple-Q (3Q) order and uniform spin scalar chirality. Upon Co overdoping (𝑥>1/3), it undergoes a shift in magnetic ordering vectors from 𝐐 m =(1/2, 0, 0) to (1/3, 0, 0). Interestingly, the spontaneous Hall effect disappeared in the overdoped regime, which was originally attributed to the loss of 3Q order. However, a question remains whether a new type of 3Q order can exist with alternating chirality in the overdoped regime. To address this, we investigated C⁢o 0.336⁢ Ta⁢S 2 using inelastic neutron scattering (INS), neutron diffraction, and optical dichroism, and found that INS data and spin-wave simulations support a 3Q order with alternating chirality. Moreover, neutron diffraction data show field-independent Bragg peaks, while linear dichroism detects no in-plane anisotropy, consistent with threefold rotation symmetry. Our data support the scenario of an alternating-chirality 3Q order in C⁢o 0.336 ⁢Ta⁢S 2 , canceling the spontaneous Hall effect. Furthermore, this study highlights a combined neutron-optical approach to identify complex spin textures.

Landau-Lifschitz-Gilbert equation↗
DOE OSTI2022

Optical Simulations for the VENUS Neutron Imaging Instrument

The VENUS Neutron Imaging instrument at the Spallation Neutron Source has gone through a multitude of optical design changes since its original conception. The goal of this report is to quantify the performance of the most recent optical design and provide insight into potential improvements to this design as needed to ensure optimal performance of the instrument. The results will come in the form of a refined and well developed simulation that provides as best a representation of the performance of the instrument as reasonably achievable. This simulation will be available in a repository alongside relevant simulation output needed to inform any future decisions on the design of the instrument.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2015

A Magnetron Sputter Deposition System for the Development of X-Ray Multilayer Optics

The project objective is to establish the capability to deposit multilayer structures for x-ray, neutron, and extreme ultraviolet (EUV) optic applications through the development of a magnetron sputtering deposition system. A specific goal of this endeavor is to combine multilayer deposition technology with the replication process in order to enhance NASA Marshall Space Flight Center's (MSFC's) position as a world leader in the design of innovative x-ray instrumentation through the development of full shell replicated multilayer optics. The development of multilayer structures are absolutely necessary in order to advance the field of x-ray astronomy by pushing the limit for observing the universe to ever-increasing photon energies (i.e., up to 200 keV or higher), well beyond Chandra's (approx.10 keV) and NuStar's (approx.75 keV) capability. The addition of multilayer technology would significantly enhance the x-ray optics capability at MSFC and allow NASA to maintain its world leadership position in the development, fabrication, and design of innovative x-ray instrumentation, which would be the first of its kind by combining multilayer technology with the mirror replication process. This marriage of these technologies would allow astronomers to see the universe in a new light by pushing to higher energies that are out of reach with today's instruments. To this aim, a magnetron vacuum sputter deposition system for the deposition of novel multilayer thin film x-ray optics is proposed. A significant secondary use of the vacuum deposition system includes the capability to fabricate multilayers for applications in the field of EUV optics for solar physics, neutron optics, and x-ray optics for a broad range of applications including medical imaging.

Broadway, David↗
DOE OSTI2025

Neutron powder diffraction, Mossbauer Spectroscopy and Optical Spectroscopy to study magnetic and nuclear lattices in Fe-based oxychlorides Ca2FeO3Cl, Sr2FeO3Cl and Sr3Fe2O5Cl2

Data for Neutron Diffraction, Mossbauer Spectoscopy and Optical Spectroscopy are contained on all three samples (Ca2FeO3Cl, Sr2FeO3Cl, and Sr3Fe2O5Cl2). Mossbauer data are in the folder "MossbauerSpectroscopy". This contains details of files and examples to read the data. The Optical Spectroscopy are in the folder "AbsorptionData", this contains one file with explanatory headers. The neutron diffraction data are in the "NeutronDiffractionData" folder. The data was collected on the HB-2A powder diffractometer at HFIR. The autoreduced files are corrected using a vanadium standard and are in arbitrary intensity units. The RawData folder contains the uncorrected data with metadata for motor positions and temperature. All measurements were collected with a constant neuton wavelength of 2.41 Angstrom. An excel spreadsheet "NeutronDiffractionData_IPTS-29118_summary" contains details for each scan. Sr3Fe2O5Cl2 data were collected at only room temperature. Ca2FeO3Cl and Sr2FeO3Cl data were collected at 4K and room temperature. The autoreduced .dat fileformat is three columns corresponding to: Two-theta, Intensity and Intensity_error.

fe-based oxychlorides↗
DOE OSTI2020

Fabrication and testing of high-performance all-metal neutron guides and axisymmetric mirrors by electrochemical replication

Neutron scattering is one of the most useful methods of studying the structure of matter, with applications to biomedical, structural, magnetic and energy-related materials. Neutron-scattering instruments are installed around research reactors or accelerator-based neutron sources, and neutron guides are critical components of these facilities. They are neutron-transport optical devices consisting of state-of-the-art mirrors often tens of meters long. Here we demonstrate a novel fabrication method of all-metallic neutron guides and axisymmetric mirrors by electroplating from precision mandrels. The process allows for the fabrication of single-piece all-metal guides of prismatic and axisymmetric shapes. We also demonstrate supermirror guides and axisymmetric focusing supermirrors produced with the same technology. We present the fabrication and tests of the multilayer-coated replicated guides and optic and show that the mandrel is reproduced with high fidelity and reliability. Furthermore, such supermirror optics will provide game-changing improvements in neutron techniques.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Design of Neutron Microscopes Equipped with Wolter Mirror Condenser and Objective Optics for High-Fidelity Imaging and Beam Transport

We present and compare the designs of three types of neutron microscopes for high-resolution neutron imaging. Like optical microscopes, and unlike standard neutron imaging instruments, these microscopes have both condenser and image-forming objective optics. The optics are glancing-incidence axisymmetric mirrors and therefore suitable for polychromatic neutron beams. The mirrors are designed to provide a magnification of 10 to achieve a spatial resolution of better than 10 μm. The resolution of the microscopes is determined by the mirrors rather than by the L/Dratio as in conventional pinhole imaging, leading to possible dramatic improvements in the signal rate. We predict the increase in the signal rate by at least two orders of magnitude for very high-resolution imaging, which is always flux limited. Furthermore, in contrast to pinhole imaging, in the microscope, the samples are placed far from the detector to allow for a bulky sample environment without sacrificing spatial resolution.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Global Microscopic Description of Nucleon-Nucleus Scattering with Quantified Uncertainties

We develop for the first time a microscopic global nucleon-nucleus optical potential with quantified uncertainties suitable for analyzing nuclear reaction experiments at next-generation rare-isotope beam facilities. Within the improved local density approximation and without any adjustable parameters, we begin by computing proton-nucleus and neutron-nucleus optical potentials from a set of five nuclear forces from chiral effective field theory for 1800 target nuclei in the mass range 12 ≤ A ≤ 242 for energies between 0 MeV < E ≲ 150 MeV. We then parameterize a global optical potential for each chiral force that depends smoothly on the projectile energy as well as the target nucleus mass number and isospin asymmetry. Uncertainty bands for elastic scattering observables are generated from a full covariance analysis of the parameters entering in the description of our global optical potential and benchmarked against existing experimental data for stable target nuclei. Since our approach is purely microscopic, we anticipate a similar quality of the model for nucleon scattering on unstable isotopes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Quantifying uncertainties due to optical potentials in one-neutron knockout reactions

One-neutron knockout reactions have been widely used to extract information about the single-particle structure of nuclei from the valley of stability to the drip lines. The interpretation of knockout data relies on reaction models, where the uncertainties are typically not accounted for. In this work, we quantify uncertainties of optical potentials used in these reaction models and propagate them, for the first time, to knockout observables using a Bayesian analysis. We study two reactions in the present paper, the first of which involves a loosely bound halo projectile, 11 Be, and the second a tightly bound projectile, 12 C. We first quantify the parametric uncertainties associated with phenomenological optical potentials. Complementing this approach, we also quantify the model uncertainties associated with the chiral forces that can be used to construct microscopic optical potentials. For the phenomenological study, we investigate the impact of the imaginary terms of the optical potential on the breakup and stripping components of the knockout cross sections as well as the impact of the angular range. For the 11 Be case, the theoretical uncertainty from the phenomenological method is on the order of the experimental uncertainty of the knockout observables; however, for the 12 C case, the theoretical uncertainty is significantly larger. Additionally, the widths of the uncertainty bands for the knockout observables obtained for the microscopic study and the phenomenological approach are of similar orders of magnitude. Based on this work we conclude that structure information inferred from the ratio of the knockout cross sections will carry a theoretical uncertainty of at least 20% for halo nuclei and at least 40% for tightly bound nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2011

Optical Sensors for Monitoring Gamma and Neutron Radiation

For safety and efficiency, nuclear reactors must be carefully monitored to provide feedback that enables the fission rate to be held at a constant target level via adjustments in the position of neutron-absorbing rods and moderating coolant flow rates. For automated reactor control, the monitoring system should provide calibrated analog or digital output. The sensors must survive and produce reliable output with minimal drift for at least one to two years, for replacement only during refueling. Small sensor size is preferred to enable more sensors to be placed in the core for more detailed characterization of the local fission rate and fuel consumption, since local deviations from the norm tend to amplify themselves. Currently, reactors are monitored by local power range meters (LPRMs) based on the neutron flux or gamma thermometers based on the gamma flux. LPRMs tend to be bulky, while gamma thermometers are subject to unwanted drift. Both electronic reactor sensors are plagued by electrical noise induced by ionizing radiation near the reactor core. A fiber optic sensor system was developed that is capable of tracking thermal neutron fluence and gamma flux in order to monitor nuclear reactor fission rates. The system provides near-real-time feedback from small- profile probes that are not sensitive to electromagnetic noise. The key novel feature is the practical design of fiber optic radiation sensors. The use of an actinoid element to monitor neutron flux in fiber optic EFPI (extrinsic Fabry-Perot interferometric) sensors is a new use of material. The materials and structure used in the sensor construction can be adjusted to result in a sensor that is sensitive to just thermal, gamma, or neutron stimulus, or any combination of the three. The tested design showed low sensitivity to thermal and gamma stimuli and high sensitivity to neutrons, with a fast response time.

Boyd, Clark D.↗