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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

General Mode Scanning Probe Microscopy

A critical part of SPM measurements is the information transfer from the probe-sample junction to the measurement system. Current information transfer methods heavily compress the information-rich data stream by averaging the data over a time interval, or via heterodyne detection approaches such as lock-in amplifiers and phase-locked loops. As a consequence, highly valuable information at the sub-microsecond time scales or information from frequencies outside the measurement band is lost. We have developed a fundamentally new approach called General Mode (G-mode), where we can capture the complete information stream from the detectors in the microscope. The availability of the complete information allows the microscope operator to analyze the data via information-theory analysis or comprehensive physical models. Furthermore, the complete data stream enables advanced data-driven filtering algorithms, multi-resolution imaging, ultrafast spectroscropic imaging, spatial mapping of multidimensional variability in material properties, etc. Though we applied this approach to scanning probe microscopy, the general philosophy of G-mode can be applied to many other modes of microscopy. G-mode data is captured by completely custom software written in LabVIEW and Matlab. The software generates the waveforms to electrically, thermally, or mechanically excite the SPM probe. It handles real-time communications with the microscope software for operations such as moving the SPM probe position and also controls other instrumentation hardware. The software also controls multiple variants of high-speed data acquisition cards to excite the SPM probe with the excitation waveform and simultaneously measure multiple channels of information from the microscope detectors at sampling rates of 1-100 MHz. The software also saves the raw data to the computer and allows the microscope operator to visualize processed or filtered data during the experiment. The software performs all these features while offering a user-friendly interface.

Somnath, Suhas↗
DOE OSTI2025

Single-shot electro-optic sampling with arbitrary terahertz polarization

With the recent development of diversity electro-optic sampling (DEOS), significant progress has been made in the range of applicability of single-shot EOS measurements, allowing broadband THz waveforms to be captured in a single shot over large temporal windows. In addition to the decrease in acquisition time compared to standard multishot data acquisition, this technique allows measurements on systems far from equilibrium with large shot-to-shot noise or with irreversible or poorly repeatable dynamics. Although DEOS has been demonstrated and verified for linearly polarized THz waveforms, we investigate the effects resulting from the presence of a secondary polarization component. This imposes new challenges for accurate waveform reconstruction, and opens the opportunity to measure out complex polarization states such as arbitrary elliptically polarized THz field. We demonstrate a single-shot diversity-electro-optic-sampling-based approach to capture both x- and y-THz fields simultaneously with a single (110)-cut EO crystal for THz polarimetry and ellipsometry over a wide range of frequencies.

Lenz, Maximilian [University of California, Los An↗
DOE OSTI2019

Integrated Geomechanics and Geophysics in Induced Seismicity: Mechanisms and Monitoring

Quantifying in-situ subsurface stresses and predicting fracture development are critical to reducing risks of induced seismicity and improving modern energy activities in the subsurface. In this work, we developed a novel integration of controlled mechanical failure experiments coupled with microCT imaging, acoustic sensing, modeling of fracture initiation and propagation, and machine learning for event detections and waveform characterization. Through additive manufacturing (3D printing), we were able to produce bassanite-gypsum rock samples with repeatable physical, geochemical and structural properties. With these "geoarchitected" rock, we provided the role of mineral texture orientation on fracture surface roughness. The impact of poroelastic coupling on induced seismicity has been systematically investigated to improve mechanistic understanding of post shut-in surge of induced seismicity. This research will set the groundwork for characterizing seismic waveforms by using multiphysics and machine learning approaches and improve the detection of low-magnitude seismic events leading to the discovery of hidden fault/fracture systems.

42 ENGINEERING↗
DOE OSTI2020

Visualization of hydraulic fracture using physics-informed clustering to process ultrasonic shear waves

Ultrasonic transmission is sensitive to the spatial variation in mechanical properties of materials due to the presence of cracks/fractures. Wave propagation through fractured media introduces changes in the frequency content, travel time and transmission coefficient of the wave. A workflow based on physics-informed unsupervised learning is developed to process the transmitted ultrasonic-shear waveforms to non-invasively visualize the geomechanical alterations due to hydraulic fracturing. Novelty of the work involves the assignment of both statistically consistent and physically consistent clusters to the measurements of shear waveforms acquired across the one axial and two frontal planes. Physically consistent/relevant information is incorporated by considering the travel time of the peak of spectral energy and transmission coefficient of the transmitted waveform. The proposed workflow generates maps of geomechanical alterations across the frontal and axial planes of the sample. The outputs of the workflow are in good agreement with independent techniques viz. acoustic emission and X-ray computed tomography. Finally, the proposed workflow can be adapted for improved fracture characterization in the subsurface when processing sonic-logging, cross-wellbore seismic or surface seismic waveform data.

42 ENGINEERING↗
DOE OSTI2018

Comprehensive Single-Shot Proteomics with FAIMS on a Hybrid Orbitrap Mass Spectrometer

Liquid chromatography (LC) prefractionation is often implemented to increase proteomic coverage; however, while effective, this approach is laborious, requires considerable sample amount, and can be cumbersome. We describe how interfacing a recently described high-field asymmetric waveform ion mobility spectrometry (FAIMS) device between a nanoelectrospray ionization (nanoESI) emitter and an Orbitrap hybrid mass spectrometer (MS) enables the collection of single-shot proteomic data with comparable depth to that of conventional two-dimensional LC approaches. This next generation FAIMS device incorporates improved ion sampling at the ESI–FAIMS interface, increased electric field strength, and a helium-free ion transport gas. With fast internal compensation voltage (CV) stepping (25 ms/transition), multiple unique gas-phase fractions may be analyzed simultaneously over the course of an MS analysis. We have comprehensively demonstrated how this device performs for bottom-up proteomics experiments as well as characterized the effects of peptide charge state, mass loading, analysis time, and additional variables. We also offer recommendations for the number of CVs and which CVs to use for different lengths of experiments. Internal CV stepping experiments increase protein identifications from a single-shot experiment to >8000, from over 100 000 peptide identifications in as little as 5 h. In single-shot 4 h label-free quantitation (LFQ) experiments of a human cell line, we quantified 7818 proteins with FAIMS using intra-analysis CV switching compared to 6809 without FAIMS. Single-shot FAIMS results also compare favorably with LC fractionation experiments. Furthermore, a 6 h single-shot FAIMS experiment generates 8007 protein identifications, while four fractions analyzed for 1.5 h each produce 7776 protein identifications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Contrasting Time-Frequency Representations for Unknown Waveform Detection

In real-world applications like spectrum management and interference detection, dealing with unseen electromagnetic waveforms is critical. Although some methods attempt to simulate open set data using generator models, they face challenges in generating synthetic samples for open set while simultaneously selecting an optimal discriminator for accurate classification. This results in difficulties capturing distinctive features across classes, especially in dynamic scenarios where new classes emerge. To detect unseen waveforms, we propose combining time and frequency domain features with cosine similarity loss to enhance feature distinctiveness and enabling more accurate predictions. This approach efficiently captures more comprehensive information than single-domain representations or approaches without cosine loss. Additionally, our model avoids generic feature vectors by extracting class-specific features during training, resulting in improved class representation. The experiment results show that this combined feature approach with cosine loss outperforms single-domain models and improves accuracy by 10\% over models without cosine loss.

99 - GENERAL AND MISCELLANEOUS↗
DOE OSTI2017

A comparison of earthquake backprojection imaging methods for dense local arrays

Backprojection imaging has recently become a practical method for local earthquake detection and location due to the deployment of densely sampled, continuously recorded, local seismograph arrays. While backprojection sometimes utilizes the full seismic waveform, the waveforms are often pre-processed and simplified to overcome imaging challenges. Real data issues include aliased station spacing, inadequate array aperture, inaccurate velocity model, low signal-to-noise ratio, large noise bursts and varying waveform polarity. We compare the performance of backprojection with four previously used data pre-processing methods: raw waveform, envelope, short-term averaging/long-term averaging and kurtosis. Our primary goal is to detect and locate events smaller than noise by stacking prior to detection to improve the signal-to-noise ratio. The objective is to identify an optimized strategy for automated imaging that is robust in the presence of real-data issues, has the lowest signal-to-noise thresholds for detection and for location, has the best spatial resolution of the source images, preserves magnitude, and considers computational cost. Imaging method performance is assessed using a real aftershock data set recorded by the dense AIDA array following the 2011 Virginia earthquake. Our comparisons show that raw-waveform backprojection provides the best spatial resolution, preserves magnitude and boosts signal to detect events smaller than noise, but is most sensitive to velocity error, polarity error and noise bursts. On the other hand, the other methods avoid polarity error and reduce sensitivity to velocity error, but sacrifice spatial resolution and cannot effectively reduce noise by stacking. Of these, only kurtosis is insensitive to large noise bursts while being as efficient as the raw-waveform method to lower the detection threshold; however, it does not preserve the magnitude information. For automatic detection and location of events in a large data set, we therefore recommend backprojecting kurtosis waveforms, followed by a second pass on the detected events using noise-filtered raw waveforms to achieve the best of all criteria.

58 GEOSCIENCES↗
DOE OSTI2023

Generative adversarial networks for scintillation signal simulation in EXO-200

Generative Adversarial Networks trained on samples of simulated or actual events have been proposed as a way of generating large simulated datasets at a reduced computational cost. In this work, a novel approach to perform the simulation of photodetector signals from the time projection chamber of the EXO-200 experiment is demonstrated. The method is based on a Wasserstein Generative Adversarial Network — a deep learning technique allowing for implicit non-parametric estimation of the population distribution for a given set of objects. Our network is trained on real calibration data using raw scintillation waveforms as input. We find that it is able to produce high-quality simulated waveforms an order of magnitude faster than the traditional simulation approach and, importantly, generalize from the training sample and discern salient high-level features of the data. In particular, the network correctly deduces position dependency of scintillation light response in the detector and correctly recognizes dead photodetector channels. Furthermore, the network output is then integrated into the EXO-200 analysis framework to show that the standard EXO-200 reconstruction routine processes the simulated waveforms to produce energy distributions comparable to that of real waveforms. Finally, the remaining discrepancies and potential ways to improve the approach further are highlighted.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

System and method for high dynamic range waveform digitization

Diverse applications from particle physics experiments to lidar are driving cost and current reduction in giga-hertz sampling rate high-resolution data conversion. Multiple imagers captures a single pixel of data and require processing at very high speed. High-bandwidth high-rate signal sampling, analog-to-digital conversion, and transfer of large amounts of data to a digital data acquisition block are required in such systems. Dynamic range, power consumption, and transfer of high-speed, high-bit width data are key implementation challenges. Data acquisition architectures optimized for specific requirements of such systems may facilitate system implementation and reduce overall system cost.

Mostafanezhad, Isar↗
DOE OSTI2019

A new approach to vibrational sum frequency generation spectroscopy using near infrared pulse shaping

In this work, we have developed a multipurpose vibrational sum frequency generation (vSFG) spectrometer that is uniquely capable of probing a broad range of chemical species, each requiring different experimental conditions, without optical realignment. Here, we take advantage of arbitrary near infrared (NIR) waveform generation using a 4 f -pulse shaper equipped with a 2D spatial light modulator (SLM) to tailor upconversion pulses to meet sample dependent experimental requirements. This report details the experimental layout, details of the SLM calibration and implementation, and the intrinsic benefits/limitations of this new approach to vSFG spectroscopy. We have demonstrated the competency of this spectrometer by achieving an ~3-fold increase in spectral resolution compared to conventional spectrometers by probing the model dimethyl sulfoxide/air interface. We also show the ability to suppress nonresonant background contributions from electrode interfaces using time delayed asymmetric waveforms that are generated by the NIR pulse shaper. Lastly, it is expected that this advancement in instrumentation will broaden the types of samples researchers can readily study using nonlinear surface specific spectroscopies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Mu2e Calorimeter Readout System

The Mu2e electromagnetic calorimeter is made of two disks of un-doped parallelepiped CsI crystals readout by SiPM. There are 674 crystals in one disk and each crystal is readout by an array of two SiPM. The readout electronics is composed of two types of modules: (1) the front-end module hosts the shaping amplifier and the high voltage linear regulator; since one front-end module is interfaced to one SiPM, a total of 2696 modules are needed for the entire calorimeter; (2) a waveform digitizer provides a further level of amplification and digitizes the SiPM signal at the sampling frequency of 200MHz with 12-bits ADC resolution; since one board digitizes the data received from 20 SiPMs, a total of 136 boards are needed. The readout system operational conditions are hostile: ionization dose of 20krads , neutron flux of 10 12 n(1MeVeq)/cm 2 , magnetic field of 1T and in vacuum level of 10 -4 Torr . A description of the readout system and qualification tests is reported.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Adaptive OFDM Radar Waveform Design for Improved Micro-Doppler Estimation

Here we analyze the performance of a wideband orthogonal frequency division multiplexing (OFDM) signal in estimating the micro-Doppler frequency of a rotating target having multiple scattering centers. The use of a frequency-diverse OFDM signal enables us to independently analyze the micro-Doppler characteristics with respect to a set of orthogonal subcarrier frequencies. We characterize the accuracy of micro-Doppler frequency estimation by computing the Cramer-Rao bound (CRB) on the angular-velocity estimate of the target. Additionally, to improve the accuracy of the estimation procedure, we formulate and solve an optimization problem by minimizing the CRB on the angular-velocity estimate with respect to the OFDM spectral coefficients. We present several numerical examples to demonstrate the CRB variations with respect to the signal-to-noise ratios, number of temporal samples, and number of OFDM subcarriers. We also analysed numerically the improvement in estimation accuracy due to the adaptive waveform design. A grid-based maximum likelihood estimation technique is applied to evaluate the corresponding mean-squared error performance.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Characterizing Photometric Flicker

The focus of this study is simply to report on the commercial availability and performance of emerging flicker meters. Commercial-meter measurements and calculations were compared against those generated by a photoelectric characterization system developed by the Pacific Northwest National Laboratory (PNNL). The results and analysis show that the three commercially available flicker meters evaluated for this study measured light-intensity waveforms and calculated essential flicker-performance characteristics and metrics similarly, both to each other and to the reference meter chosen as an accuracy benchmark. Some differences in performance were found, however, when measurements were taken of light-intensity waveforms with significant high-frequency content – greater than the dominant 120 Hz found in many products at full output. Such conditions may be found in light sources that employ pulse-width modulation to achieve their target light output (e.g., intensity or color). If the meter was not appropriately configured (e.g., sampling frequency was too low), or if proper configuration was not possible given meter constraints (e.g., maximum number of available data points), then the waveform characteristics were not accurately captured, often resulting in the calculation of flicker metrics that deviated significantly from the reference.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2015

Atomic-scale electrochemistry on the surface of a manganite

The doped manganese oxides (manganites) have been widely studied for their colossal magnetoresistive effects, for potential applications in oxide spintronics, electroforming in resistive switching devices, and are materials of choice as cathodes in modern solid oxide fuel cells. However, little experimental knowledge of the dynamics of the surfaces of perovskite manganites at the atomic scale exists. Here, through in-situ scanning tunnelling microscopy (STM), we demonstrate atomic resolution on samples of La 0.625 Ca 0.375 MnO 3 grown on (001) SrTiO 3 by pulsed laser deposition (PLD). Furthermore, by applying triangular DC waveforms of increasing amplitude to the STM tip, and measuring the tunnelling current, we demonstrate the ability to both perform and monitor surface electrochemical processes at the atomic level, including, for the first time in a manganite, formation of single and multiple oxygen vacancies, disruption of the overlying manganite layers, and removal and deposition of individual atomic units or clusters. Our work paves the way for better understanding of surface oxygen reactions in these systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Internal arcing and lightning strike damage in short carbon fiber reinforced thermoplastic composites

Short carbon fiber reinforced thermoplastic composites (S-CFRTP) are currently used in interior parts of aircraft such as electronic circuitry and assemblies, and their usage in aircraft's exterior is also being studied. In this paper, we present a lightning strike study on S-CFRTPs. High performance thermoplastics such as a polyphenylene sulfide (PPS) reinforced with 50% weight (wt.) short carbon fiber (CF), a polyphenyl sulfone (PPSU) reinforced with 25 % wt. Short CF and a acrylonitrile butadiene styrene (ABS) with 20 % wt. short CF were tested against artificial lightning strikes. All samples were prepared using an extrusion compression molding (ECM) technique. A modified component A (100 kA) of lightning waveform, as defined by SAE ARP 5412-B, was applied. High speed imaging, thermography, scanning electron microscopy (SEM) and ultrasonic non-destructive evaluation were performed to understand the effect of lightning strikes on the thermoplastic panels. The results show that electrical conductivity of the composite, thermal stability of the polymers, and CF orientation significantly affected the damage from artificial lightning strikes. PPS composite had the highest resilience against lightning strike damage, retaining 95% and 89% residual flexural strength and modulus, respectively. CF exfoliation due to internal arcing was observed in the carbon fiber-reinforced ABS polymer (CF-ABS) composite. CF exfoliation damage has been reported for the first time.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Void-free Copper Electrodeposition in High Aspect Ratio, Full Wafer Thickness Through-Silicon Vias with Endpoint Detection

High density interconnects are required for increased input/output for microelectronics applications, incentivizing the development of Cu electrochemical deposition (ECD) processes for high aspect ratio through-silicon vias (TSVs). This work outlines Cu ECD processes for 62.5 μ m diameter TSVs, etched into a 625 μ m thick silicon substrate, a 10:1 aspect ratio. Cu ECD in high aspect ratio features relies on a delicate balance of electrolyte composition, solution replenishment, and applied voltage. Implementing a CuSO 4 -H 2 SO 4 electrolyte, which contains suppressor and a low chloride concentration, allows for a tunable relationship between applied voltage and localized deposition in the vias. A stepped potential waveform was applied to move the Cu growth front from the bottom of the via to the top. Sample characterization was performed through mechanical cross-sections and X-ray computed tomography (CT) scans. The CT scans revealed small seam voids in the Cu electrodeposit, and process parameters were tuned accordingly to produce void-free Cu features. During the voltage-controlled experiments, measured current data showed a characteristic current minimum, which was identified as an endpoint detection method for Cu deposition in these vias. We believe this is the first report of this novel endpoint detection method for TSV filling.

42 ENGINEERING↗
DOE OSTI2022

Electro-optic sampling based characterization of broad-band high efficiency THz-FEL

Extremely high beam-to-radiation energy conversion efficiencies can be obtained in a THz FEL using a strongly tapered helical undulator at the zero-slippage resonant condition, where a circular waveguide is used to match the radiation group velocity to the electron beam longitudinal velocity. In this paper we report on the first electro-optic sampling (EOS) based measurements of the broadband THz FEL radiation pulses emitted in this regime. The THz field waveforms are reconstructed in the spatial and temporal domains using multi-shot and single-shot EOS schemes respectively. The measurements are performed varying the input electron beam energy in the undulator providing insights on the complex dynamics in a waveguide FEL.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Ultra-fast hadronic calorimetry

Calorimeters for particle physics experiments with integration time of a few ns will substantially improve the capability of the experiment to resolve event pileup and to reject backgrounds. In this paper the time development of hadronic showers induced by 30 and 60 GeV positive pions and 120 GeV protons is studied using Monte Carlo simulation and beam tests with a prototype of a sampling steel-scintillator hadronic calorimeter. In the beam tests, scintillator signals induced by hadronic showers in steel are sampled with a period of 0.2 ns and precisely time-aligned in order to study the average signal waveform at various locations with respect to the beam particle impact. Simulations of the same setup are performed using the MARS15 code. Both simulation and test beam results suggest that energy deposition in steel calorimeters develop over a time shorter than 2 ns providing opportunity for ultra-fast calorimetry. As a result, simulation results for an “ideal” calorimeter consisting exclusively of bulk tungsten or copper are presented to establish the lower limit of the signal integration window.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗