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At least 1,783 records · Page 99
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Radiant energy required for infrared neural stimulation

Infrared neural stimulation (INS) has been proposed as an alternative method to electrical stimulation because of its spatial selective stimulation. Independent of the mechanism for INS, to translate the method into a device it is important to determine the energy for stimulation required at the target structure. Custom-designed, flat and angle polished fibers, were used to deliver the photons. By rotating the angle polished fibers, the orientation of the radiation beam in the cochlea could be changed. INS-evoked compound action potentials and single unit responses in the central nucleus of the inferior colliculus (ICC) were recorded. X-ray computed tomography was used to determine the orientation of the optical fiber. Maximum responses were observed when the radiation beam was directed towards the spiral ganglion neurons (SGNs), whereas little responses were seen when the beam was directed towards the basilar membrane. The radiant exposure required at the SGNs to evoke compound action potentials (CAPs) or ICC responses was on average 18.9 ± 12.2 or 10.3 ± 4.9 mJ/cm 2 , respectively. For cochlear INS it has been debated whether the radiation directly stimulates the SGNs or evokes a photoacoustic effect. The results support the view that a direct interaction between neurons and radiation dominates the response to INS.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

First principles based screen for identification of transparent conductors

We present methods for screening semiconductors as transparent conductors leading to a simple application dependent fitness function. We report a simple first principles based screen amenable to high throughput calculations for transparent conductors. These include the effects of doping on transparency, which can be important. In particular, doping leads to conduction accompanied by losses in transparency, both of which are materials dependent, but rarely considered in computational materials selection. We consider both the Drude contribution to optical conductivity, as well as new interband transitions that arise as a material is doped. This leads to a simple application dependent optical and electrical fitness function (OEF) that can be applied to semiconductors to identify materials that may be useful transparent conductors. The OEF goes beyond the frequently discussed criteria of suitable band gap and low effective mass. Finally, we illustrate this by application to a number of proposed p-type transparent conducting materials.

14 SOLAR ENERGY↗
DOE OSTI2013

The new bern PET cyclotron, its research beam line, and the development of an innovative beam monitor detector

The new Bern cyclotron laboratory aims at industrial radioisotope production for PET diagnostics and multidisciplinary research by means of a specifically conceived beam transfer line, terminated in a separate bunker. In this framework, an innovative beam monitor detector based on doped silica and optical fibres has been designed, constructed, and tested. Scintillation light produced by Ce and Sb doped silica fibres moving across the beam is measured, giving information on beam position, shape, and intensity. The doped fibres are coupled to commercial optical fibres, allowing the read-out of the signal far away from the radiation source. This general-purpose device can be easily adapted for any accelerator used in medical applications and is suitable either for low currents used in hadrontherapy or for currents up to a few {mu}A for radioisotope production, as well as for both pulsed and continuous beams.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Machine learning to analyze images of shocked materials for precise and accurate measurements

A supervised machine learning algorithm, called locally adaptive discriminant analysis (LADA), has been developed to locate boundaries between identifiable image features that have varying intensities. LADA is an adaptation of image segmentation, which includes techniques that find the positions of image features (classes) using statistical intensity distributions for each class in the image. In order to place a pixel in the proper class, LADA considers the intensity at that pixel and the distribution of intensities in local (nearby) pixels. This paper presents the use of LADA to provide, with statistical uncertainties, the positions and shapes of features within ultrafast images of shock waves. We demonstrate the ability to locate image features including crystals, density changes associated with shock waves, and material jetting caused by shock waves. This algorithm can analyze images that exhibit a wide range of physical phenomena because it does not rely on comparison to a model. LADA enables analysis of images from shock physics with statistical rigor independent of underlying models or simulations.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Design of a robot-automated flat plate/reflection geometry x-ray diffraction setup for accelerated materials discovery and structural screening

Here, we report the design, construction, and automation of a flat plate sample loading, alignment, and data acquisition system for X-ray diffraction measurements in reflection geometry implemented at the Stanford Synchrotron Radiation Lightsource. The system is built onto a single platform, enabling facile transferability, and is compartmentalized into sample storage, sample transfer, and sample position/alignment segments. The core feature of this system is a six-axis robotic arm that offers a large range of highly reproducible and programable movements. The degrees of freedom of the robot arm enable adaptability in which movements can be modified to fit various beamline environments and sample configurations. Samples are housed on 3D printed sample mounts, which are arranged onto a 6 × 2 array of sample cassettes capable of holding 7 samples. Using sample mounts designed for solid oxide electrolysis button cells (SOECs), the maximum tray capacity is 84 samples, which can be aligned and run in ~ 24 hours with long exposure scans. The sample array is additionally capable of accommodating a range of sample sizes and geometries due to the rapid 3D printed fabrication. The components of the setup will be described in detail and performance will be demonstrated with a set of representative SOEC and XRD standard samples. Opportunities for future developments and integration with the automated setup are summarized.

08 HYDROGEN↗
DOE OSTI2013

THE BLACK HOLE-BULGE MASS RELATION OF ACTIVE GALACTIC NUCLEI IN THE EXTENDED CHANDRA DEEP FIELD-SOUTH SURVEY

We present results from a study to determine whether relations-established in the local universe-between the mass of supermassive black holes (SMBHs) and their host galaxies are in place at higher redshifts. We identify a well-constructed sample of 18 X-ray-selected, broad-line active galactic nuclei (AGNs) in the Extended Chandra Deep Field-South Survey with 0.5 < z < 1.2. This redshift range is chosen to ensure that Hubble Space Telescope (HST) imaging is available with at least two filters that bracket the 4000 A break, thus providing reliable stellar mass estimates of the host galaxy by accounting for both young and old stellar populations. We compute single-epoch, virial black hole (BH) masses from optical spectra using the broad Mg II emission line. For essentially all galaxies in our sample, their total stellar mass content agrees remarkably well, given their BH masses, with local relations of inactive galaxies and active SMBHs. We further decompose the total stellar mass into bulge and disk components separately with full knowledge of the HST point-spread function. We find that {approx}80% of the sample is consistent with the local M{sub BH}-M{sub *,{sub Bulge}} relation even with 72% of the host galaxies showing the presence of a disk. In particular, bulge-dominated hosts are more aligned with the local relation than those with prominent disks. We further discuss the possible physical mechanisms that are capable of building up the stellar mass of the bulge from an extended disk of stars over the subsequent 8 Gyr.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Boosting H I -Galaxy Cross-Clustering Signal through Higher-Order Cross-Correlations

After reionization, neutral hydrogen (${\rm H\, \small {I}}$) traces the large-scale structure (LSS) of the Universe, enabling ${\rm H\, \small {I}}$ intensity mapping (IM) to capture the LSS in 3D and constrain key cosmological parameters. We present a new framework utilizing higher-order cross-correlations to study ${\rm H\, \small {I}}$ clustering around galaxies, tested using real-space data from the IllustrisTNG300 simulation. This approach computes the joint distributions of k-nearest neighbor (kNN) optical galaxies and the ${\rm H\, \small {I}}$ brightness temperature field smoothed at relevant scales (the kNN-field framework), providing sensitivity to all higher-order cross-correlations, unlike two-point statistics. To simulate ${\rm H\, \small {I}}$ data from actual surveys, we add random thermal noise and apply a simple foreground cleaning model, filtering out Fourier modes of the brightness temperature field with k ∥ < k min,∥ . Under current levels of thermal noise and foreground cleaning, typical of a Canadian Hydrogen Intensity Mapping Experiment (CHIME)-like survey, the ${\rm H\, \small {I}}$-galaxy cross-correlation signal in our simulations, using the kNN-field framework, is detectable at >30σ across r = [3, 12] h –1 Mpc. In contrast, the detectability of the standard two-point correlation function (2PCF) over the same scales depends strongly on the foreground filter: a sharp k ∥ filter can spuriously boost detection to 8σ due to position-space ringing, whereas a less sharp filter yields no detection. Nonetheless, we conclude that kNN-field cross-correlations are robustly detectable across a broad range of foreground filtering and thermal noise conditions, suggesting their potential for enhanced constraining power over 2PCFs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Variational preparation of the thermofield double state of the Sachdev-Ye-Kitaev model

Here, we provide an algorithm for preparing the thermofield double (TFD) state of the Sachdev-Ye-Kitaev (SYK) model without the need for an auxiliary bath. Following previous work, the TFD can be cast as the approximate ground state of a Hamiltonian, H TFD . Using variational quantum circuits, we propose and implement a gradient-based algorithm for learning parameters that find this ground state, an application of the variational quantum eigensolver. Concretely, we find shallow quantum circuits that prepare the ground state of H TFD for the q = 4 SYK model for N = 8 Majoranas per side. For N = 12, we achieve a variational energy within 1% of the true ground-state energy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Quantum advantage for differential equation analysis

Quantum algorithms for differential equation solving, data processing, and machine learning potentially offer an exponential speedup over all known classical algorithms. However, there also exist obstacles to obtaining this potential speedup in useful problem instances. The essential obstacle for quantum differential equation solving is that outputting useful information may require difficult postprocessing, and the essential obstacle for quantum data processing and machine learning is that inputting the data is a difficult task just by itself. In this study, we demonstrate that, when combined, these difficulties solve one another. We show how the output of quantum differential equation solving can serve as the input for quantum data processing and machine learning, allowing dynamical analysis in terms of principal components, power spectra, and wavelet decompositions. To illustrate this, we consider continuous-time Markov processes on epidemiological and social networks. These quantum algorithms provide an exponential advantage over existing classical Monte Carlo methods.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Ultrabroadband optical parametric chirped-pulse amplifier using a fan-out periodically poled crystal with spectral spatial dispersion

Based on the full two-dimensional characteristics of the quasi-phase-matched fan-out periodically poled crystal, a scalable and engineerable scheme for ultrabroadband optical parametric chirped-pulse amplification is proposed, which can significantly broaden the gain bandwidth by the spatial separation of different frequency components of the signal pulse and manipulation of the distribution of the pump beam along the fan-out direction of the crystal. The theoretical analysis shows that the signal pulse can be amplified with minimal spectrum narrowing, and the initial spectrum can be broadened considerably if needed. Based on this scheme, using a fan-out periodically poled 5% mol MgO-doped congruent lithium niobate with a configuration of 5x0.5x5 mm{sup 3} and two pump beams, the 3.3-{mu}m middle-infrared ultrabroadband optical parametric chirped-pulse amplifier is designed. The numerical computation results confirm that the -3 dB gain bandwidth of this amplifier exceeds 320 nm and can be further broadened.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Leveraging Qubit Loss Detection in Fault-Tolerant Quantum Algorithms

Qubit loss errors constitute a dominant source of noise in many quantum hardware systems, particularly in neutral-atom quantum computers. We develop a theoretical framework to effectively detect and correct loss errors in logical algorithms and leverage such loss information in decoding. Considering general quantum error correction codes and logical circuits, we introduce a delayed-erasure decoder for experimentally motivated error models which leverages information from delayed loss detection to accurately correct loss errors, even when the precise moment of the error is unknown. Using this decoder, we identify strategies for detecting and correcting loss errors based on the logical circuit structure. For deep circuits prior to logical measurement, we explore methods to integrate loss detection into syndrome extraction with minimal overhead, identifying optimal strategies depending on the qubit loss fraction in the noise and hardware capabilities. In contrast, we find that many key algorithmic subroutines involve frequent gate teleportation, shortening the circuit depth before logical measurement and naturally replacing qubits with no additional experimental overhead. We simulate this setting using a toy model algorithm for small-angle synthesis and find a significant performance improvement as the loss fraction increases. These results provide a path forward for advancing large-scale fault-tolerant quantum computation in systems with loss error detection.

atoms↗
DOE OSTI2012

Development of a flexible optical fiber based high resolution integrated PET/MRI system

Purpose: The simultaneous measurement of PET and magnetic resonance imaging (MRI) is an emerging field for molecular imaging research. Although optical fiber based PET/MRI systems have advantages on less interference between PET and MRI, there is a drawback in reducing the scintillation light due to the fiber. To reduce the problem, the authors newly developed flexible optical fiber bundle based block detectors and employed them for a high resolution integrated PET/MRI system. Methods: The flexible optical fiber bundle used 0.5 mm diameter, 80 cm long double clad fibers which have dual 12 mm Multiplication-Sign 24 mm rectangular inputs and a single 24 mm Multiplication-Sign 24 mm rectangular output. In the input surface, LGSO scintillators of 0.025 mol.% (decay time: {approx}31 ns: 0.9 mm Multiplication-Sign 1.3 mm Multiplication-Sign 5 mm) and 0.75 mol.% (decay time: {approx}46 ns: 0.9 mm Multiplication-Sign 1.3 mm Multiplication-Sign 6 mm) were optically coupled in depth direction to form depth-of-interaction detector, arranged in 11 Multiplication-Sign 13 matrix and optically coupled to the fiber bundle. The two inputs of the bundle are bent for 90 Degree-Sign , bound to one, and are optically coupled to a Hamamatsu 1-in. square position sensitive photomultiplier tube. Results: Light loss due to the fiber bundle could be reduced and the performance of the block detectors was improved. Eight optical fiber based block detectors (16 LGSO blocks) were arranged in a 56 mm diameter ring to form a PET system. Spatial resolution and sensitivity were 1.2 mm full-width at half-maximum and 1.2% at the central field-of-view, respectively. Sensitivity change was less than 1% for 2 Degree-Sign C temperature changes. This PET system was integrated with a 0.3 T permanent magnet MRI system which has 17 cm diameter hole at the yoke area for insertion of the PET detector ring. There was no observable interference between PET and MRI. Simultaneous imaging of PET and MRI was successfully performed for small animal studies. Conclusions: The authors confirmed that the developed high resolution PET/MRI system is promising for molecular imaging research.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Influence of gradation on failure mode of saturated sand at particle scale

Extensive research has been reported in the literature to characterize the failure mode of dry sand using various experimental techniques such as surface optical imaging, photo-elastic materials, three-dimensional (3D) computed tomography (CT), and 3D synchrotron micro-computed tomography (SMT). However, there is a limited literature about the behavior of saturated sand. This paper presents the results of axisymmetric triaxial compression (ATC) experiments that were conducted on saturated sand specimens. The behavior of specimens composed of a uniform sand with grain size between US sieves #40 and #50 is compared to specimens conducted on the same sand that has a wider gradation. 3D SMT technique was used to acquire 3D scans while shearing the specimens to probe localized events that are completely missed or misinterpreted when analyzing ATC measurements based on global standard measurements. The results show a higher effective principal stress ratio (EPSR) for the non-uniform specimen and a thicker shear band when compared to uniform specimen.

Elnur, Mohammed [University of Tennessee]↗
DOE OSTI2020

bifacial_radiance: a python package for modeling bifacial solar photovoltaic systems

bifacial_radiance is a national-laboratory-developed, community-supported, open-source toolkit that provides a set of functions and classes for simulating the performance of bifacial photovoltaic (PV) systems. (Bifacial PV modules collect light on the front as well as the rear side.) bifacial_radiance automates calculations of PV system layout and performance to use along with the popular ray-tracing software tool RADIANCE (Ward, 1994). Specific algorithms include design and layout of PV modules, reflective ground surfaces, shading obstructions, and irradiance calculations throughout the system, among others. bifacial_radiance is an important component of a growing ecosystem of open-source tools for solar energy (William F Holmgren et al., 2018).

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Raman Lidar (RL) Instrument Handbook

The Raman lidar at the ARM Climate Research Facility (ACRF) Southern Great Plains (SGP) Central Facility (SGPRL) is an active, ground-based laser remote sensing instrument that measures height and time resolved profiles of water vapor mixing ratio and several cloud- and aerosol-related quantities. The system is a non-commercial custom-built instrument developed by Sandia National Laboratories specifically for the ARM Program. It is fully computer automated, and will run unattended for many days following a brief (~5-minute) startup period. The self-contained system (requiring only external electrical power) is housed in a climate-controlled 8’x8’x20’ standard shipping container.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Tardigrade: Summary (LL20-AM-sensor)

Tardigrade is an effort to create small, passive remote sensor for material detection and identification. The microbolometer based sensor design uses custom bandpass filter bands combined with tuned thermal expansion materials in a ruggedized lens housing to provide passive mechanical correction for optical changes across a wide temperature range. This requires developing computational tools to model and predict thermal performance of meta-materials composed of multiple structured base materials and void-space, along with matching and developing 3D print technology to demonstrate the housing. Current efforts in the project are in 3 areas: material design algorithm development (transitioning into full 3D material design space), multi-material additive manufacturing process exploration, and sensor/optics design and engineering.

42 ENGINEERING↗
DOE OSTI2025

Nitridation of atomically smooth (111) diamond surfaces using a low temperature Penning plasma discharge

Diamond is a material with a wide band gap that can host a variety of isolated paramagnetic defects, called “color centers”1. These color centers have attractive optical and magnetic properties suitable for quantum applications including quantum computing, nanophotonics and quantum sensing. The most common one is the negatively charged nitrogen vacancy (NV) color center. For quantum sensing, it is desirable to reduce the distance between the NV center and the analyte by using shallow color centers in order to increase sensitivity. In this context, the diamond surface termination is especially critical. The appropriate surface termination is required to stabilize the color centers and mitigate surface magnetic noise. The nitrogen termination of diamond has been postulated as highly desirable for the NV color center. The goal of this project is to take advantage of an electron beam-generated ExB low temperature plasma developed by the Princeton Collaborative Low Temperature Plasma Research Facility (PCRF) at the Princeton Plasma Physics Laboratory (PPPL) to nitridate the surface of (100) diamond single crystals with minimal surface damage. In this reactor, the use of a magnetized plasma enables gentle processing of materials sensitive to ion damage. This is in strong contrast to radiofrequency plasma processing reactors which are known to etch and sputter the surface. XPS measurements indicate the incorporation of nitrogen and oxygen atoms at the surface in similar amounts. XAS measurements confirm the nitridation and indicate that the nitrogen termination is different from the nitrogen termination obtained using radiofrequency plasma treatment4. The combination of these results indicates the formation of amid species at the (100) diamond surface that are promising for the stabilization of NV centers for quantum sensing.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Three-dimensional Boltzmann-hydro Code for Core-collapse in Massive Stars. III. A New Method for Momentum Feedback from Neutrino to Matter

We present a new method for neutrino-matter coupling in multi-dimensional radiation-hydrodynamic simulations of core-collapse supernovae (CCSNe) with the full Boltzmann neutrino transport. This development is motivated by the fact that accurate conservation of momentum is required for reliable numerical modelings of CCSN dynamics including a recoil of proto-neutron stars (PNSs). The new method is built on a hybrid approach in which we use the energy-momentum tensor of neutrinos to compute the momentum feedback from neutrino to matter in the optically thick region while we employ the collision term in the optically thin region. In this method we utilize a general relativistic description of radiation-hydrodynamics with angular moments, which allows us to evaluate the momentum feedback from neutrino to matter without inconsistency with our Boltzmann solver. We demonstrate that the new method substantially improves the accuracy of linear momentum conservation in our CCSN simulations under reasonable angular resolutions in momentum space, alleviating the difficulty in giving the diffusion limit precisely with the discrete ordinate ($S_n$) method. It is the first ever demonstration that the PNS kick can be handled directly and properly in multi-dimensional radiation-hydrodynamic simulations with the full Boltzmann neutrino transport.

79 ASTRONOMY AND ASTROPHYSICS↗