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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Real-Time Vehicle-Mounted Multistatic Ground Penetrating Radar Imaging System for Buried Object Detection

A multistatic ground penetrating radar system is described, capable of real-time imaging and object detection. The radar consists of 16 transmitter and receiver pairs mounted across the front of a vehicle. The transmitters operate sequentially with all receivers activated for each transmit pulse. The resulting frame of 256 multistatic time signals is processed into an image using a tomographic reconstruction technique. In this paper we describe the system architecture, signal conditioning, and reconstruction algorithm for producing a sequence of images in real time as the vehicle travels across the ground. We demonstrate a robust image post-processing method that separates the bright spot corresponding to the dominant buried object in an image frame from the background. This is essential before calculating an energy-based statistic for automatic detection of buried objects. This spot ratio detection statistic, based on energy both inside and outside the spot, is shown to be not only more stationary than spot energy (i.e. mostly free of localized trends due to changing ground conditions), but also more powerful as a detection statistic. Finally, we demonstrate that multistatic imaging significantly improves the detection performance over more conventional monostatic array processing.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Performance studies of atomic layer deposited microchannel plate electron multipliers

Microchannel plate (MCP) photon counting, event timing, imaging detectors have found wide use in astronomical, remote sensing, and biological imaging applications. Novel MCP technology using borosilicate glass microcapillary array substrates functionalized by the application of resistive and secondary emissive layers using atomic layer deposition (ALD) techniques has the potential to outperform traditional MCP technology. Using ALD techniques to functionalize the MCPs allow customization of parameters like gain and resistance independently from the glass substrate. Borosilicate substrates have many advantages over traditional micro-capillary arrays, including low radioactive content, higher open area ratios, low outgassing, and high operational stability. These ALD MCPs can be manufactured in large areas (400 cm 2 ) providing a unique solution for many timing/imaging applications. ALD MCPs can withstand the processing temperatures required for high temperature deposition of III-V materials, such as Gallium Nitride, for UV photocathodes with high quantum efficiencies (QE) in the Near-UV (similar to 100-380 nm). We present the effects of different ALD configurations on the gain (magnitude and uniformity), resistance, imaging, background and detection efficiency, and how these parameters change during lifetime testing. Here, we also present the QE of ALD MCPs and various QE enhancement techniques.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Designing of sparse 2D arrays for Lamb wave imaging using coarray concept

2D ultrasonic arrays have considerable application potential in Lamb wave based SHM systems, since they enable equivocal damage imaging and even in some cases wave-mode selection. Recently, it has been shown that the 2D arrays can be used in SHM applications in a synthetic focusing (SF) mode, which is much more effective than the classical phase array mode commonly used in NDT. The SF mode assumes a single element excitation of subsequent transmitters and off-line processing the acquired data. In the simplest implementation of the technique, only single multiplexed input and output channels are required, which results in significant hardware simplification. Application of the SF mode for 2D arrays creates additional degrees of freedom during the design of the array topology, which complicates the array design process, however, it enables sparse array designs with performance similar to that of the fully populated dense arrays. In this paper we present the coarray concept to facilitate synthesis process of an array’s aperture used in the multistatic synthetic focusing approach in Lamb waves-based imaging systems. In the coherent imaging, performed in the transmit/receive mode, the sum coarray is a morphological convolution of the transmit/receive sub-arrays. It can be calculated as the set of sums of the individual sub-arrays’ elements locations. The coarray framework will be presented here using a an example of a star-shaped array. The approach will be discussed in terms of beampatterns of the resulting imaging systems. Both simulated and experimental results will be included.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Multimodal (Non)Linear Optical Nanoimaging and Nanospectroscopy

This article highlights recent advances in linear and nonlinear spectral nanoimaging. The described developments are motivated by the need to characterize molecular and material systems noninvasively with nanometer spatial and femtosecond temporal resolution. Indeed, the ability to image and chemically characterize heterogeneous interfaces with joint nano–femto resolution is a prerequisite to advancing our fundamental understanding of processes as diverse as heterogeneous catalysis, microbial communication, and energy flow in pristine/defect-containing low-dimensional quantum materials, to name a few. We describe pioneering work and recent demonstrations of (non)linear optical nanoimaging and nanospectroscopy, with an emphasis on high spatial resolution measurements conducted under ambient laboratory conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2008

NASA Tech Briefs, February 2008

Topics discussed include: Optical Measurement of Mass Flow of a Two-Phase Fluid; Selectable-Tip Corrosion-Testing Electrochemical Cell; Piezoelectric Bolt Breakers and Bolt Fatigue Testers; Improved Measurement of B(sub 22) of Macromolecules in a Flow Cell; Measurements by a Vector Network Analyzer at 325 to 508 GHz; Using Light to Treat Mucositis and Help Wounds Heal; Increasing Discharge Capacities of Li-(CF)(sub n) Cells; Dot-in-Well Quantum-Dot Infrared Photodetectors; Integrated Microbatteries for Implantable Medical Devices; Oxidation Behavior of Carbon Fiber-Reinforced Composites; GIDEP Batching Tool; Generic Spacecraft Model for Real-Time Simulation; Parallel-Processing Software for Creating Mosaic Images; Software for Verifying Image-Correlation Tie Points; Flexcam Image Capture Viewing and Spot Tracking; Low-Pt-Content Anode Catalyst for Direct Methanol Fuel Cells; Graphite/Cyanate Ester Face Sheets for Adaptive Optics; Atomized BaF2-CaF7 for Better-Flowing Plasma-Spray Feedstock; Nanophase Nickel-Zirconium Alloys for Fuel Cells; Vacuum Packaging of MEMS With Multiple Internal Seal Rings; Compact Two-Dimensional Spectrometer Optics; and Fault-Tolerant Coding for State Machines.

Source record↗
DOE OSTI2014

Low dimension structures and devices for new generation photonic technology

Low dimensional structures and devices are the key technological building blocks for new generation of electronic and photonic technology. Such structures and devices show novel properties and can be integrated into systems for wide applications in many areas, including medical, biological and military and advancement of science. In this invited talk, I will present the main results achieved in our competitive research program which aims to explore the application of the mesoscopic structures in light source, manipulation and imaging and integrate them into advanced systems. In the light source aspect, we have for the first time developed graphene mode-locked lasers which are in the process of commercialization. Nanocrystal Si embedded in dielectrics was formed by ion implantation and subsequent annealing. Si light emitting devices with external quantum efficiency of about 2.9×10{sup −3}% for visible emission were demonstrated at room temperature and the color of emitted light can be tuned electrically from violet to white by varying the injected current. In light manipulation, loss compensation of surface plasmon polaritons (SPPs) using quantum well (QW) gain media was studied theoretically and demonstrated experimentally. The SPP propagation length was effectively elongated several times through electrical pumping. One and two microring resonators based on silicon on insulator and III-V semiconductors technologies have been successfully fabricated and they can be used as filter and switch in the photonic circuit. In imaging, both SPP and low dimension structures are investigated and resolution far beyond diffraction limit in visible range has been realized. The integration of the components in the three aspects into complicated systems is on the way.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Imaging nanoscale carrier, thermal, and structural dynamics with time-resolved and ultrafast electron energy-loss spectroscopy

Time-resolved and ultrafast electron energy-loss spectroscopy (EELS) is an emerging technique for measuring photoexcited carriers, lattice dynamics, and near-fields across femtosecond to microsecond timescales. When performed in either a specialized scanning transmission electron microscope or ultrafast electron microscope (UEM), time-resolved and ultrafast EELS can directly image charge carriers, lattice vibrations, and heat dissipation following photoexcitation or applied bias. Yet, recent advances in theoretical calculations and electron optics are often required to realize the full potential of ultrafast EEL spectrum imaging. Here, in this review, we present a comprehensive overview of the recent progress in the theory and instrumentation of time-resolved and ultrafast EELS. We begin with an introduction to the technique, followed by a physical description of the loss function. We outline approaches for calculating and interpreting ground-state and transient EEL spectra spanning low-loss plasmons to core-level excitations analogous to x-ray absorption. We then survey the current state of time-resolved and ultrafast EELS techniques beyond photon-induced near-field electron microscopy, highlighting abilities to image carrier and thermal dynamics. Finally, we examine future directions enabled by emerging technologies, including electron beam monochromation, in situ and operando cells, laser-free UEM, and high-speed direct electron detectors. These advances position time-resolved and ultrafast EELS as a critical tool for uncovering nanoscale dynamic processes in quantum materials and solar energy conversion devices.

Computational methods↗
DOE OSTI2010

Two-dimensional image edge enhancement in the two-phonon diffraction

We suggest using the two-phonon Bragg scattering regime for two-dimensional image edge enhancement by means of acousto-optic (AO) diffraction on a single sound wave. Image edge enhancement is demonstrated in the first diffraction order by using an AO cell made of the TeO{sub 2} single crystal. To explain this effect, a three-dimensional model of AO interaction is proposed, which takes into account the angular selectivity of diffraction both in the plane of Bragg scattering and in the plane orthogonal to it. (optical data processing)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Imaging an aligned polyatomic molecule with laser-induced electron diffraction

Laser-induced electron diffraction is an evolving tabletop method that aims to image ultrafast structural changes in gas-phase polyatomic molecules with sub-Ångstro¨m spatial and femtosecond temporal resolutions. Here we demonstrate the retrieval of multiple bond lengths from a polyatomic molecule by simultaneously measuring the C–C and C–H bond lengths in aligned acetylene. Our approach takes the method beyond the hitherto achieved imaging of simple diatomic molecules and is based on the combination of a 160 kHz mid-infrared few-cycle laser source with full three-dimensional electron–ion coincidence detection. Our technique provides an accessible and robust route towards imaging ultrafast processes in complex gas-phase molecules with atto- to femto-second temporal resolution.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Bulk reconstruction and non-isometry in the backwards-forwards holographic black hole map

The backwards-forwards map, introduced as a generalization of the non-isometric holographic maps of the black hole interior of Akers, Engelhardt, Harlow, Penington, and Vardhan to include non-trivial dynamics in the effective description, has two possible formulations differing in when the post-selection is performed. While these two forms are equivalent on the set of dynamically generated states — states formed from unitary time evolution acting on well-defined initial configurations of infalling matter — they differ on the generic set of states necessary to describe the apparent world of the infalling observer. We show that while both versions successfully reproduce the Page curve, the version involving post-selection as the final step, dubbed the backwards-forwards-post-selection (BFP) map, has the desirable properties of being non-isometric but isometric on average and providing state-dependent reconstruction of bulk operators, while the other version does not. Thus the BFP map is a suitable non-isometric code describing the black hole interior including interior interactions.

3-D Image Reconstruction↗
DOE OSTI2014

A new architecture for fast ultrasound imaging

Some ultrasound imaging applications require high frame rate, for example 3D imaging and automated inspections of large components. Being the signal-processing throughput of the system the main bottleneck, parallel beamforming is required to achieve hundreds to thousands of images per second. Simultaneous A-scan line beamforming in all active channels is required to reach the intended high frame rate. To this purpose, a new parallel beamforming architecture that exploits the currently available processing resources available in state-of-the-art FPGAs is proposed. The work aims to get the optimal resource usage, high scalability and flexibility for different applications. To achieve these goals, the basic beamforming function is reformulated to be adapted to the DSP-cell architecture of state-of-the-art FPGAs. This allows performing simultaneous dynamic focusing on multiple A-scan lines. Some realistic examples are analyzed, evaluating resource requirements and maximum operating frequency. For example, a 128-channel system, with 128 scan lines and acquiring at 20 MSPS, can be built with 4 mid-range FPGAs, achieving up to 18000 frames per second, just limited by the maximum PRF. The gold standard Synthetic Transmit Aperture method (also called Total Focusing Method) can be carried out in real time at a processing rate of 140 high-resolution images per second (16 cm depth on steel)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Multi-bit quantum random number generation by measuring positions of arrival photons

We report upon the realization of a novel multi-bit optical quantum random number generator by continuously measuring the arrival positions of photon emitted from a LED using MCP-based WSA photon counting imaging detector. A spatial encoding method is proposed to extract multi-bits random number from the position coordinates of each detected photon. The randomness of bits sequence relies on the intrinsic randomness of the quantum physical processes of photonic emission and subsequent photoelectric conversion. A prototype has been built and the random bit generation rate could reach 8 Mbit/s, with random bit generation efficiency of 16 bits per detected photon. FPGA implementation of Huffman coding is proposed to reduce the bias of raw extracted random bits. The random numbers passed all tests for physical random number generator.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Squeezed Light Stimulated Raman Scattering (SRS) Microscopy for Bioenergy Applications

Stimulated Raman scattering (SRS) microscopy using picosecond near-IR pulses have provided a great penetration depth with reduced fluorescence interference when imaging biological samples for bioenergy applications. These tools have provided insight into 1) tracking the degradation of chemical composites in biomass feedstocks to investigate the recalcitrant factors during the deconstruction processes, 2) monitoring the production of chemicals in photosynthetic plants and wood-digesting microorganisms, and 3) probing plant-bacteria interactions. However, the above processes are usually slow and require continuous imaging for an extended period. This is challenging for classic SRS because the laser power needed to achieve enough sensitivity causes photodamage in the samples during such long experiments. Quantum-squeezed light with reduced noise in the intensity quadrature can improve the sensitivity of classic SRS microscopy beyond the shot noise limit. The successful squeezing of one of the picosecond pulses in the above SRS will improve sensitivity and reduce photodamage, greatly expanding the range of studies available to SRS microscopy.

BIOMASS FUELS↗
DOE OSTI2010

Simulation of image detectors in radiology for determination of scatter-to-primary ratios using Monte Carlo radiation transport code MCNP/MCNPX

Purpose: The purpose of this study was to compare and validate three methods to simulate radiographic image detectors with the Monte Carlo software MCNP/MCNPX in a time efficient way. Methods: The first detector model was the standard semideterministic radiography tally, which has been used in previous image simulation studies. Next to the radiography tally two alternative stochastic detector models were developed: A perfect energy integrating detector and a detector based on the energy absorbed in the detector material. Validation of three image detector models was performed by comparing calculated scatter-to-primary ratios (SPRs) with the published and experimentally acquired SPR values. Results: For mammographic applications, SPRs computed with the radiography tally were up to 44% larger than the published results, while the SPRs computed with the perfect energy integrating detectors and the blur-free absorbed energy detector model were, on the average, 0.3% (ranging from -3% to 3%) and 0.4% (ranging from -5% to 5%) lower, respectively. For general radiography applications, the radiography tally overestimated the measured SPR by as much as 46%. The SPRs calculated with the perfect energy integrating detectors were, on the average, 4.7% (ranging from -5.3% to -4%) lower than the measured SPRs, whereas for the blur-free absorbed energy detector model, the calculated SPRs were, on the average, 1.3% (ranging from -0.1% to 2.4%) larger than the measured SPRs. Conclusions: For mammographic applications, both the perfect energy integrating detector model and the blur-free energy absorbing detector model can be used to simulate image detectors, whereas for conventional x-ray imaging using higher energies, the blur-free energy absorbing detector model is the most appropriate image detector model. The radiography tally overestimates the scattered part and should therefore not be used to simulate radiographic image detectors.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2011

A generic, geometric cocalibration method for a combined system of fluorescence molecular tomography and microcomputed tomography with arbitrarily shaped objects

Purpose: A combined system of fluorescence molecular tomography and microcomputed tomography (FMT and mCT) can provide molecular and anatomical information of small animals in a single study with intrinsically coregistered images. The anatomical information provided by the mCT subsystem is commonly used as a reference to locate the fluorophore distribution or as a priori structural information to improve the performance of FMT. Therefore, the transformation between the coordinate systems of the subsystem needs to be determined in advanced. Methods: A cocalibration method for the combined system of FMT and mCT is proposed. First, linear models are adopted to describe the galvano mirrors and the charge-coupled device (CCD) camera in the FMT subsystem. Second, the position and orientation of the galvano mirrors are determined with the input voltages of the galvano mirrors and the markers, whose positions are predetermined. The position, orientation and normalized pixel size of the CCD camera are obtained by analysing the projections of a point-like marker at different positions. Finally, the orientation and position of sources and the corresponding relationship between the detectors and their projections on the image plane are predicted. Because the positions of the markers are acquired with mCT, the registration of the FMT and mCT could be realized by direct image fusion. Results: The accuracy and consistency of this method in the presence of noise is evaluated by computer simulation. Next, a practical implementation for an experimental FMT and mCT system is carried out and validated. The maximum prediction error of the source positions on the surface of a cylindrical phantom is within 0.375 mm and that of the projections of a point-like marker is within 0.629 pixel. Finally, imaging experiments of the fluorophore distribution in a cylindrical phantom and a phantom with a complex shape demonstrate the feasibility of the proposed method. Conclusions: This method is universal in FMT and mCT, which could be performed with no restriction on the system geometry, calibration phantoms or imaging objects.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Collimator design for a dedicated molecular breast imaging-guided biopsy system: Proof-of-concept

Purpose: Molecular breast imaging (MBI) is a dedicated nuclear medicine breast imaging modality that employs dual-head cadmium zinc telluride (CZT) gamma cameras to functionally detect breast cancer. MBI has been shown to detect breast cancers otherwise occult on mammography and ultrasound. Currently, a MBI-guided biopsy system does not exist to biopsy such lesions. Our objective was to consider the utility of a novel conical slant-hole (CSH) collimator for rapid (<1 min) and accurate monitoring of lesion position to serve as part of a MBI-guided biopsy system. Methods: An initial CSH collimator design was derived from the dimensions of a parallel-hole collimator optimized for MBI performed with dual-head CZT gamma cameras. The parameters of the CSH collimator included the collimator height, cone slant angle, thickness of septa and cones of the collimator, and the annular areas exposed at the base of the cones. These parameters were varied within the geometric constraints of the MBI system to create several potential CSH collimator designs. The CSH collimator designs were evaluated using Monte Carlo simulations. The model included a breast compressed to a thickness of 6 cm with a 1-cm diameter lesion located 3 cm from the collimator face. The number of particles simulated was chosen to represent the count density of a low-dose, screening MBI study acquired with the parallel-hole collimator for 10 min after a {approx}150 MBq (4 mCi) injection of Tc-99m sestamibi. The same number of particles was used for the CSH collimator simulations. In the resulting simulated images, the count sensitivity, spatial resolution, and accuracy of the lesion depth determined from the lesion profile width were evaluated. Results: The CSH collimator design with default parameters derived from the optimal parallel-hole collimator provided 1-min images with error in the lesion depth estimation of 1.1 {+-} 0.7 mm and over 21 times the lesion count sensitivity relative to 1-min images acquired with the current parallel-hole collimator. Sensitivity was increased via more vertical cone slant angles, larger annular areas, thinner cone walls, shorter cone heights, and thinner radiating septa. Full width at half maximum trended in the opposite direction as sensitivity for all parameters. There was less error in the depth estimates for less vertical slant angles, smaller annular areas, thinner cone walls, cone heights near 1 cm, and generally thinner radiating septa. Conclusions: A Monte Carlo model was used to demonstrate the feasibility of a CSH collimator design for rapid biopsy application in molecular breast imaging. Specifically, lesion depth of a 1-cm diameter lesion positioned in the center of a typical breast can be estimated with error of less than 2 mm using circumferential count profiles of images acquired in 1 min.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1981

Advanced InSb monolithic Charge Coupled Infrared Imaging Devices (CCIRID)

The continued development of monolithic InSb charge coupled infrared imaging devices (CCIRIDs) is discussed. The processing sequence and structural design of 20-element linear arrays are discussed. Also, results obtained from radiometric testing of the 20-element arrays using a clamped sample-and-hold output circuit are reported. The design and layout of a next-generation CCIRID chip are discussed. The major devices on this chip are a 20 by 16 time-delay-and-integration (TDI) area array and a 100-element linear imaging array. The development of a process for incorporating an ion implanted S(+) planar channel stop into the CCIRID structure and the development of a thin film transparent photogate are also addressed. The transparent photogates will increase quantum efficiency to greater than 70% across the 2.5 to 5.4 micrometer spectral region in future front-side illuminated CCIRIDs.

Koch, T. L.↗