SEARCH · Engineering Papers

Results for “WAVELENGTHS”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26

All sources NASA NTRS DOE OSTI

DOE OSTI2023

Time-varying gradient metasurface with applications in all-optical beam steering

Integrating the large, subpicosecond nonlinear optical response of epsilon-near-zero (ENZ) materials with the broad design freedoms of plasmonic metasurfaces shows potential for creating rapidly modulated optical devices with possible applications in telecommunications, sensing, and reactive beam steering. In this work, we experimentally investigate a metasurface consisting of a plasmonic gradient array on a thin layer of indium tin oxide (ITO), characterize how incident probe pulses diffract from a system as it is being dynamically modulated by a pump pulse at wavelengths near the ENZ region. Angular shifts in the diffraction orders are observed and can be principally attributed to the adiabatic wavelength conversion of the probe as it witnesses the temporal change of index induced by the pump. Of note, the asymmetric gradient metasurface, considered to be a blazed diffraction grating, shows significantly different dynamic responses for different diffraction orders. The free-space wavelength shift to +1 and -1 diffraction orders is 6 and 12 nm, resulting in steering angle changes of 0.65 and 1.5°, respectively.

42 ENGINEERING↗

DOE OSTI2021

Nonlinear X-ray Optics

Novel X-ray free-electron lasers (XFELs) are capable of producing radiation with unprecedented properties. Specifically, their ultrashort coherent X-ray pulses can generate extreme peak intensities where ordinary rules of light-matter interaction may no longer apply, and nonlinear processes start to become important. XFELs have made it possible to observe some of the most important coherent non-sequential nonlinearities, including X-ray-optical sum frequency generation (SFG), X-ray second harmonic generation (XSHG), two-photon absorption (TPA) and nonlinear two-photon Compton scattering (2PCS). In particular, the 2PCS experiment has led to unexpected results, namely the observation of a substantial anomalous red shift in the energy of photons generated by nonlinear two-photon X-ray Compton scattering in beryllium. The energy shift is in addition to the predicted nonlinear Compton shift and was neither expected from extrapolations from linear X-ray interactions nor from nonlinear effects at optical wavelengths. Our results suggest a novel nonlinear scattering mechanism that can only be observed at high fields at X-ray wavelengths, where the photon energy is a significant fraction of the electron rest mass (and thus a significant momentum transfer to the electron occurs during the scattering) and where the interaction is not dominated by the quiver motion of the electron in the field (ponderomotive potential) as is usually the case at longer (optical) wavelengths. The goal of this research project was the investigation of fundamental nonlinear X-ray-matter interactions. As these processes are typically weak, part of this research is the exploration of more efficient nonlinear X-ray processes by studying novel mechanisms including solid-state effects, the assistance of optical radiation and novel phase-matching techniques. These experiments require extremely large X-ray field strengths, such as produced by XFELs. Nonlinear X-ray effects can lead to important applications in many research fields. For example, it could lead to instantaneous plasma diagnostics for materials in extreme conditions, as a method for combining atomic-scale structural sensitivity with chemical specificity, or as a probe of electron dynamics in solids on the attosecond (1 as = 10 -18 s) time- and Ångstrom (10 -10 m) length scales. In addition, a detailed understanding of nonlinear X-ray matter interactions is crucial for understanding and extending the limits of structural determination at high intensity such as in serial femto-crystallography. The results could have a profound impact on advanced XFEL light sources such as the LCLS-II.

47 OTHER INSTRUMENTATION↗

DOE OSTI2022

High Efficiency InGaN LEDs Emitting in Green, Amber and Beyond (Final Report)

This project focuses on developing high efficiency light emitting diodes (LEDs) with green, amber, and longer wavelengths using two compatible material systems based on III-nitride and II-IV-nitride semiconductor heterostructures. The proposed approach uses low-indium-content InGaN and ZnGeN 2 or ZnSnN 2 heterostructure quantum wells (QWs) as the active regions for high efficiency green and amber LEDs, and therefore to advance high efficiency color-mixed white LED technology. This approach takes advantage of the increased flexibility, afforded by the incorporation of the II-IV-nitrides into the III-nitride layers, to tune the QW active region to lower the emission wavelengths and to increase the electron-hole wave function overlap. This strategy paves a new way to extend the InGaN QW LED emission wavelength without using high-indium-content InGaN. An industrially preferable metalorganic chemical vapor deposition (MOCVD) method was used to develop the growth of ZnGeN 2 and ZnSnN 2 that are compatible with the InGaN growth. The unique dual chamber MOCVD instrument at OSU was used in this project. This program created an opportunity for the two institutions (The Ohio State University and Case Western Reserve University) with complementary expertise to perform this work. Two graduate students (Md Rezaul Karim (OSU) and Benthara Hewage Dinushi Jayatunga (CWRU)) gained experience in MOCVD growth and various characterization methods including scanning electron microscopy, x-ray diffraction spectroscopy, x-ray photoemission spectroscopy, Hall measurements, cathodoluminescence and photoluminescence. Both students successfully defended their PhD dissertations in April/May 2021. Both Karim and Jayatunga have joined Intel as engineers in June/July 2021. Another two graduate students Kaitian Zhang (OSU) and Chenxi Hu (CWRU) joined the project team since spring 2021 to continue on this project. They were trained on MOCVD epitaxy of InGaN QWs and materials characterization including SEM, AFM, PL, CL, XRD, Hall measurements and electroluminescence. A third student, Vijay Gopal Thirupakuzi Vangipuram (OSU), who joined the group in fall 2021 to perform LED fabrication and characterization. The key research accomplishments of the project include: (1) Successful development of MOCVD epitaxy of single crystalline ZnGeN 2 and ZnSnN 2 . MOCVD growth parameters that determine the stoichiometry of ZnGeN 2 and ZnSnN 2 films were identified. (2) Experimentally determined the band offsets between GaN/ZnGeN 2 and GaN/ZnGaSnN 2 hetero-interfaces, which agree very well with the theoretical predictions. (3) Demonstrated the incorporation of thin ZnGeN 2 layer in InGaN QWs. Proof-of-concept of the InGaN-ZnGeN 2 QW design demonstrated as much as 80 nm of red shift without increasing In composition or QW thickness. (4) InGaN/ZnGeN 2 QWs emitting at 480 nm achieved IQE of 47%. Resulted from this project, 7 journal articles were published, and 9 conference papers were presented.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Studies of optical and chemical properties of aged and fresh biomass burning absorbing aerosols for climate models

Particulate emissions from burning fuels from sub-Saharan Africa is currently poorly characterized. With increasing population and industrialization, emissions are expected to grow. Optical methods for measuring light absorption in the ultraviolet (UV) and visible (vis) regions of the spectrum are crucial for understanding the optical properties of BB aerosols (Bond and Bergstrom, 2006; Lack and Cappa, 2010; Moschos et al., 2021). One such instrument is the dual-spot AE33 model aethalometer is a common filter-based instrument that can be used to measure aerosol absorption properties (Hansen et al., 1984). This instrument has many figures of merit; however, the method's limitations include potential biases from scattering within the filter material, multiple scattering effects of the particles, filter loading (i.e. particle shadowing), and the need for wavelength-specific correction factors (Cλ), which depend on accurate intercomparison with other in situ techniques (Bond et al., 1999; Collaud Coen et al., 2010). This work aims to: 1. Optically characterize BB aerosol generated from African fuel 2. Correct the aethalometer at multiple wavelengths 3. Parametrize these correction factors. 4. Combusting the same fuels with two difference tube furnace systems assess the general applicability of this flexible means of producing BB aerosol. This was accomplished by conducting laboratory studies at Los Alamos National Laboratory (LANL) and North Carolina A&T State University (NCA&T), where aethalometer measurements were compared to in situ optical measurements. Mass cross sections of BB aerosol from these under-studied fuels will be determined along with their wavelength dependence.

09 BIOMASS FUELS↗

DOE OSTI2025

Characterization of High Speed Optical and Magnetic Interactions in Superconducting Nanowire Single Photon Detectors

Single-photon detectors are essential tools for quantum photonics. The ideal single photon detector would exhibit a quantum efficiency (QE) of 100% (i.e. no false negatives), zero dark photon counts per second (i.e. no false positives), zero dead time (i.e. the detector is capable of detecting one photon immediately after another), and zero jitter (i.e. the electrical signal produced by the detector perfectly reproduces the timing of the input photon signal). Commercially available avalanche photodiodes (APDs) have generally performed reasonably well for visible wavelengths but they perform poorly at longer wavelengths. For wavelengths spanning the near- ultraviolet (UV) to the mid- infrared (IR), superconducting nanowire single photon detectors (SNSPDs) can exhibit quantum efficiencies exceeding 90% with dark count rates and timing jitter roughly an order of magnitude less than is typically seen in APDs. While SNSPDSs are now commercially available from several small businesses, fundamental questions about the nature of photon interactions with superconducting nanostructures remain.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2026

Solutions to Droop and the Green Gap by Novel Carrier Injection

Long-wavelength (green, yellow, red) visible light-emitting diodes (LEDs) have historically been inefficient compared to blue light-emitters in the III-nitrides. This is due to many factors, including poor material quality due to the low growth temperatures required for high Incomposition InGaN quantum wells (QWs), and the polar nature of the III-nitride crystal structure. Spontaneous and piezoelectric polarization in the III-nitrides causes enhanced quantum-confined Stark effect (QCSE), which spatially separates electrons and holes and reduces radiative recombination (ie: light output) from the devices. Polarization in the crystal also induces additional potential barriers that electrons and holes must cross over before entering the QWs where they can recombine to emit light. Both of these polarization effects worsen as emission wavelength increases, making blue III-nitride LEDs are the most efficient and red III-nitride LEDs the least efficient. The focus of this project has been solving the latter polarization-related issue through the implementation of V-defects in long wavelength LEDs. V-defects are morphological defects which are commonly observed in c-plane III-nitrides. They are observed as hexagonal pyramid-shaped depressions on the c-plane surface, with six semipolar sidewalls. They typically form at the apex of threading dislocations (TDs) under conditions of kinetically-limited growth and low growth-temperature. They were initially thought to be detrimental to LED performance and much early work focused on eliminating them entirely from III-nitride devices. However, over the past decade work has emerged that indicate that they can improve LED performance by allowing electrons and holes to bypass the polarization-induced barriers present in the c-plane and directly enter the QWs of an LED. This is due to the semipolar nature of the V-defect sidewall: these sidewalls are thin and lack the polarization-induced barriers which prevent carriers easily moving between layers. V-defects have since been determined to be an efficient avenue by which to inject electrons and holes into the c-plane QWs where they can recombine to emit light. Throughout this project we have explored lateral injection through a variety of methods: simulation (Task 2), epitaxial growth of V-defect and non-V-defect LEDs (Tasks 1, 3, 4, 5, 6), and advanced characterization methods (Task 7). All tasks have been completed. A description of each task completed follows from this section.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

An EvoDevo Study of Salmonid Visual Opsin Dynamics and Photopigment Spectral Sensitivity

Salmonids are ideal models as many species follow a distinct developmental program from demersal eggs and a large yolk sac to hatching at an advanced developmental stage. Further, these economically important teleosts inhabit both marine- and freshwaters and experience diverse light environments during their life histories. At a genome level, salmonids have undergone a salmonid-specific fourth whole genome duplication event (Ss4R) compared to other teleosts that are already more genetically diverse compared to many non-teleost vertebrates. Thus, salmonids display phenotypically plastic visual systems that appear to be closely related to their anadromous migration patterns. This is most likely due to a complex interplay between their larger, more gene-rich genomes and broad spectrally enriched habitats; however, the molecular basis and functional consequences for such diversity is not fully understood. This study used advances in genome sequencing to identify the repertoire and genome organization of visual opsin genes (those primarily expressed in retinal photoreceptors) from six different salmonids [Atlantic salmon ( Salmo salar ), brown trout ( Salmo trutta ), Chinook salmon ( Oncorhynchus tshawytcha ), coho salmon ( Oncorhynchus kisutch ), rainbow trout ( Oncorhynchus mykiss ), and sockeye salmon ( Oncorhynchus nerka )] compared to the northern pike ( Esox lucius ), a closely related non-salmonid species. Results identified multiple orthologues for all five visual opsin classes, except for presence of a single short-wavelength-sensitive-2 opsin gene. Several visual opsin genes were not retained after the Ss4R duplication event, which is consistent with the concept of salmonid rediploidization. Developmentally, transcriptomic analyzes of Atlantic salmon revealed differential expression within each opsin class, with two of the long-wavelength-sensitive opsins not being expressed before first feeding. Also, early opsin expression in the retina was located centrally, expanding dorsally and ventrally as eye development progressed, with rod opsin being the dominant visual opsin post-hatching. Modeling by spectral tuning analysis and atomistic molecular simulation, predicted the greatest variation in the spectral peak of absorbance to be within the Rh2 class, with a ∼40 nm difference in λ max values between the four medium-wavelength-sensitive photopigments. Overall, it appears that opsin duplication and expression, and their respective spectral tuning profiles, evolved to maximize specialist color vision throughout an anadromous lifecycle, with some visual opsin genes being lost to tailor marine-based vision.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2022

Impact of Solid State Roadway Lighting on Melatonin in Humans

Introduction: In 2009, the World Health Organization identified vehicle crashes, both injury-related and fatal, as a public health hazard. Roadway lighting has long been used to reduce crashes and improve the safety of all road users. Ocular light exposure at night can suppress melatonin levels in humans. At sufficient light levels, all visible light wavelengths can elicit this response, but melatonin suppression is maximally sensitive to visible short wavelength light. With the conversion of roadway lighting to solid state sources that have a greater short wavelength spectrum than traditional sources, there is a potential negative health impact through suppressed melatonin levels to roadway users and those living close to the roadway. This paper presents data on the impact of outdoor roadway lighting on salivary melatonin in three cohorts of participants: drivers, pedestrians, and those experiencing light trespass in their homes. Methods: In an outdoor naturalistic roadway environment, healthy participants (N = 29) each being assigned to a cohort of either pedestrian, driver, or light trespass experiment, were exposed to five different solid state light sources with differing spectral emissions and one no lighting condition. Salivary melatonin measurements were made under an average roadway luminance of 1.0 cd/m2 (IES RP-18 Roadway Lighting Requirements for expressway roads) with a corneal melanopic Equivalent Daylight Illuminances (EDI) ranging from 0.22 to 0.86 lux. Results: The results indicate that compared to the no roadway lighting condition, the roadway light source spectral content did not significantly impact salivary melatonin levels in the participants in any of the cohorts. Conclusions: These data show that recommended levels of street lighting for expressway roads do not elicit an acute suppression of salivary melatonin and suggest that the health benefit of roadway lighting for traffic safety is not compromised by an acute effect on salivary melatonin.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2021

Pipeline Monitoring Using Highly Sensitive Vibration Sensor Based on Fiber Ring Cavity Laser

A vibration fiber sensor based on a fiber ring cavity laser and an interferometer based single-mode-multimode-single-mode (SMS) fiber structure is proposed and experimentally demonstrated. The SMS fiber sensor is positioned within the laser cavity, where the ring laser lasing wavelength can be swept to an optimized wavelength using a simple fiber loop design. To obtain a better signal-to-noise ratio, the ring laser lasing wavelength is tuned to the maximum gain region biasing point of the SMS transmission spectrum. A wide range of vibration frequencies from 10 Hz to 400 kHz are experimentally demonstrated. In addition, the proposed highly sensitive vibration sensor system was deployed in a field-test scenario for pipeline acoustic emission monitoring. An SMS fiber sensor is mounted on an 18” diameter pipeline, and vibrations were induced at different locations using a piezoelectric transducer. The proposed method was shown to be capable of real-time pipeline vibration monitoring.

47 OTHER INSTRUMENTATION↗

DOE OSTI2022

New Identifications and Multiwavelength Properties of Extragalactic Fermi Gamma-Ray Sources in the SPT-SZ Survey Field

he fourth Fermi Large Area Telescope catalog (4FGL) contains 5064 $\ γ$-ray sources detected at high significance, but 26% of them still lack associations at other wavelengths. The SPT-SZ survey, conducted between 2008 and 2011 with the South Pole Telescope (SPT), covers 2500 deg 2 of the southern sky in three millimeter-wavelength (mm) bands and was used to construct a catalog of nearly 5000 emissive sources. In this study, we introduce a new cross-matching scheme to search for multiwavelength counterparts of extragalactic $\ γ$-ray sources using a mm catalog. We apply a Poissonian probability to evaluate the rate of spurious false associations and compare the multiwavelength associations from the radio, mm, near-infrared, and X-ray with 4FGL $\ γ$-ray sources. In the SPT-SZ survey field, 85% of 4FGL sources are associated with mm counterparts. These mm sources include 94% of previously associated 4FGL sources and 56% of previously unassociated 4FGL sources. The latter group contains 40 4FGL sources for which SPT has provided the first identified counterparts. Nearly all of the SPT-associated 4FGL sources can be described as flat-spectrum radio quasars or blazars. We find that the mm band is the most efficient wavelength for detecting $\ γ$-ray blazars when considering both completeness and purity. We also demonstrate that the mm band correlates better to the $\ γ$-ray band than the radio or X-ray bands. With the next generation of CMB experiments, this technique can be extended to greater sensitivities and more sky area to further complete the identifications of the remaining unknown $\ γ$-ray blazars.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

Uniform Recalibration of Common Spectrophotometry Standard Stars onto the CALSPEC System Using the SuperNova Integral Field Spectrograph

Abstract We calibrate spectrophotometric optical spectra of 32 stars commonly used as standard stars, referenced to 14 stars already on the Hubble Space Telescope–based CALSPEC flux system. Observations of CALSPEC and non-CALSPEC stars were obtained with the SuperNova Integral Field Spectrograph over the wavelength range 3300–9400 Å as calibration for the Nearby Supernova Factory cosmology experiment. In total, this analysis used 4289 standard-star spectra taken on photometric nights. As a modern cosmology analysis, all presubmission methodological decisions were made with the flux scale and external comparison results blinded. The large number of spectra per star allows us to treat the wavelength-by-wavelength calibration for all nights simultaneously with a Bayesian hierarchical model, thereby enabling a consistent treatment of the Type Ia supernova cosmology analysis and the calibration on which it critically relies. We determine the typical per-observation repeatability (median 14 mmag for exposures ≳5 s), the Maunakea atmospheric transmission distribution (median dispersion of 7 mmag with uncertainty 1 mmag), and the scatter internal to our CALSPEC reference stars (median of 8 mmag). We also check our standards against literature filter photometry, finding generally good agreement over the full 12 mag range. Overall, the mean of our system is calibrated to the mean of CALSPEC at the level of ∼3 mmag. With our large number of observations, careful cross-checks, and 14 reference stars, our results are the best calibration yet achieved with an integral-field spectrograph, and among the best calibrated surveys.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

A global study of hygroscopicity-driven light-scattering enhancement in the context of other in situ aerosol optical properties

The scattering and backscattering enhancement factors (ƒ(RH) and ƒ b (RH)) describe how aerosol particle light scattering and backscattering, respectively, change with relative humidity (RH). They are important parameters in estimating direct aerosol radiative forcing (DARF). In this study we use the dataset presented in Burgos et al. (2019) that compiles ƒ(RH) and ƒ b (RH) measurements at three wavelengths (i.e., 450, 550 and 700 nm) performed with tandem nephelometer systems at multiple sites around the world. We present an overview of ƒ(RH) and ƒ b (RH) based on both long-term and campaign observations from 23 sites representing a range of aerosol types. The scattering enhancement shows a strong variability from site to site, with no clear pattern with respect to the total scattering coefficient. In general, higher ƒ(RH) is observed at Arctic and marine sites, while lower values are found at urban and desert sites, although a consistent pattern as a function of site type is not observed. The backscattering enhancement ƒ b (RH) is consistently lower than ƒ(RH) at all sites, with the difference between ƒ(RH) and ƒ b (RH) increasing for aerosol with higher ƒ(RH). This is consistent with Mie theory, which predicts higher enhancement of the light scattering in the forward than in the backward direction as the particle takes up water. Our results show that the scattering enhancement is higher for PM 1 than PM 10 at most sites, which is also supported by theory due to the change in scattering efficiency with the size parameter that relates particle size and the wavelength of incident light. At marine-influenced sites this difference is enhanced when coarse particles (likely sea salt) predominate. For most sites, ƒ(RH) is observed to increase with increasing wavelength, except at sites with a known dust influence where the spectral dependence of ƒ(RH) is found to be low or even exhibit the opposite pattern. The impact of RH on aerosol properties used to calculate radiative forcing (e.g., single-scattering albedo, ω 0 , and backscattered fraction, b) is evaluated. The single-scattering albedo generally increases with RH, while b decreases. The net effect of aerosol hygroscopicity on radiative forcing efficiency (RFE) is an increase in the absolute forcing effect (negative sign) by a factor of up to 4 at RH = 90 % compared to dry conditions (RH < 40 %). Because of the scarcity of scattering enhancement measurements, an attempt was made to use other more commonly available aerosol parameters (i.e., ω 0 and scattering Ångström exponent, α sp ) to parameterize ƒ(RH). The majority of sites (75 %) showed a consistent trend with ω 0 (higher ƒ(RH = 85 %) for higher ω 0 ), while no clear pattern was observed between ƒ(RH = 85 %) and αsp. This suggests that aerosol ω 0 is more promising than α sp as a surrogate for the scattering enhancement factor, although neither parameter is ideal. Nonetheless, the qualitative relationship observed between ω 0 and ƒ(RH) could serve as a constraint on global model simulations.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2024

Shortwave Array Spectroradiometer-Hemispheric (SAS-He): design and evaluation

A novel ground-based radiometer, referred to as the Shortwave Array Spectroradiometer-Hemispheric (SAS-He), is introduced. This radiometer uses the shadow-band technique to report total irradiance and its direct and diffuse components frequently (every 30 s) with continuous spectral coverage (350–1700 nm) and moderate spectral (~2.5 nm ultraviolet–visible and ~6 nm shortwave-infrared) resolution. The SAS-He's performance is evaluated using integrated datasets collected over coastal regions during three field campaigns supported by the US Department of Energy's Atmospheric Radiation Measurement (ARM) program, namely the (1) Two-Column Aerosol Project (TCAP; Cape Cod, Massachusetts), (2) Tracking Aerosol Convection Interactions Experiment (TRACER; in and around Houston, Texas), and (3) Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE; La Jolla, California). We compare (i) aerosol optical depth (AOD) and total optical depth (TOD) derived from the direct irradiance, as well as (ii) the diffuse irradiance and direct-to-diffuse ratio (DDR) calculated from two components of the total irradiance. As part of the evaluation, both AOD and TOD derived from the SAS-He direct irradiance are compared to those provided by a collocated Cimel sunphotometer (CSPHOT) at five (380, 440, 500, 675, 870 nm) and two (1020, 1640 nm) wavelengths, respectively. Additionally, the SAS-He diffuse irradiance and DDR are contrasted with their counterparts offered by a collocated multifilter rotating shadowband radiometer (MFRSR) at six (415, 500, 615, 675, 870, 1625 nm) wavelengths. Overall, reasonable agreement is demonstrated between the compared products despite the challenging observational conditions associated with varying aerosol loadings and diverse types of aerosols and clouds. For example, the AOD- and TOD-related values of root mean square error remain within 0.021 at 380, 440, 500, 675, 870, 1020, and 1640 nm wavelengths during the three field campaigns.

47 OTHER INSTRUMENTATION↗

DOE OSTI2026

Findings of the African Combustion Aerosol Collaborative Intercomparison Analysis (ACACIA) Pilot Project to Understand the Optical Properties of Biomass Burning Smoke

Africa is a critical source of biomass burning (BB) aerosols, and its importance is increasing. The African Combustion Aerosol Collaborative Intercomparison Analysis (ACACIA) Pilot Project set to optically characterize BB aerosol generated from sub-Saharan African fuels. We used a photoacoustic spectrometer as a reference instrument to determine the multiple-scattering correction factor C λ for an AE33 aethalometer at three wavelengths, which produced weighted mean values of C 370 =3.69, C 470 =5.65, and C 520 =6.39. C λ increased with wavelength and C 370 was statistically independent of the others, suggesting a single C λ is insufficient, especially in BB scenarios. While a dependence of C λ on burning state was not found, C λ was shown to strongly relate to particle single scattering albedo (SSA, ω). When Cλ was plotted against SSA, values slowly rose at low SSA values, followed by a sharp rise around an SSA of ∼ 0.9; indicating a larger correction needed for less absorbing aerosol. A number of functions operating on either SSA or C λ were explored and the best function was -C λ /(1-C λ )=Aω+B. This is an important parametrization of C λ specifically geared towards BB aerosol from African fuels under different aging states, and is of particular importance for future field work in that continent. An Ångström matrix plot shows that African BB aerosol can have values more akin to dust, which demonstrates that these fuels are distinct in their wavelength dependence from more typical BB aerosol. Lastly, we examined the mass extinction and absorbance cross sections for BB aerosol generated for the same fuels with two different tube furnace setups. Not only is this combustion method flexible, it was found to be reproducible between labs.

47 OTHER INSTRUMENTATION↗

DOE OSTI2024

AE33 Aethalometer Records at RMBL [AMF2] from April 2022 to October 2023

The dataset presents atmospheric mass loadings of black carbon (BC) and brown carbon (BrC), during the Surface Atmosphere Integrated Field Laboratory (SAIL) campaign that took place from 2021 – 2023 in Gothic, CO. A Magee Scientific aethalometer (model AE33) was deployed at the Rocky Mountain Biological Laboratory, 200 m north of AMF2 to monitor mass loadings of optically absorbing aerosols. The instrument inlet was equipped with a BGI SCC 1.829 ambient cyclone with a particle cutoff of 2.5 μm and placed 5 m above ground level. The dataset reports hour-resolved BC mass loadings at 370, 470, 520, 590, 660, 880, and 950 (BC370, BC470, BC 520, BC590, BC660, BC880, BC950 in ng/m3) reported by the instrument built-in algorithm, which calculates mass loadings from the rate of change of the attenuation of light transmitted through the aerosol-laden filter. BC880 is the operationally defined reference of the BC concentration. Hour-resolved absorbance at each wavelength were calculated from their respective mass absorption cross-section in inverse megameters (Mm-1). The absorption Angstrom exponent (AAE) for BrC and BC were calculated for each hour. BrC AAE (AAE_BrC) was calculated from the slope of Log(wavelength) versus Log(absorbance) based on the measurements at 370, 470, and 520 nm. BC AAE (AAE_BrC) was calculated from the slope of Log(wavelength) versus Log(absorbance) based on the measurements at 590, 660, 880, and 950 nm. The aethalometer record spans time periods of 4/5/2022 – 10/3/2022 and 12/8/2022 – 10/9/2023. The ambient CO2 concentration recorded by a Vaisala CARBOCAP carbon dioxide probe GMP343 is also reported in ppm.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2020

CTIR spectrometer for large area assessment of gas emissions

Systems for determining the presence and distribution of gas emissions in an area are provided. For example, a system may include one or more light detectors and one or more reflectors and/or one more retroreflectors disposed around the perimeter, a light source configured to emit light at a plurality of wavelengths towards the one or more light detectors and/or the one or more reflectors and/or one or more retroreflectors, and one or more processors configured to receive information representing light intensity detected by the one or more light detectors, respectively at each of the plurality of wavelengths and determine gases present in each path based on the light intensity detected by the respective detector at each of the plurality of wavelengths and distribution thereof. The path being either light source-respective detector, light source-respective reflector-respective detector or light source-respective retroreflector-respective detector. Other system may not use reflectors and/or retroreflectors.

47 OTHER INSTRUMENTATION↗

DOE OSTI2021

Methods of epsilon-near-zero optical modulation

A method of optical modulation in a non-resonant epsilon-near-zero (EMZ) plasmonic electro-optical modulator is provided. An optical carrier is injected into a waveguide optically coupled to a layer of transparent conductive material having an epsilon-near-zero (ENZ) wavelength. The transparent conductive material layer constitutes a portion of a capacitive structure that includes a gate dielectric layer. A time-varying bias voltage applied across the gate dielectric layer shifts the ENZ wavelength toward the carrier wavelength, and thereby impresses a phase modulation pattern on the carrier wave.

Wood, Michael↗

DOE OSTI2022

Optical device for in-line and real-time monitoring of microorganisms

A multi-wavelength laser diode based optical sensor system capable of monitoring the dynamics and physiological changes of a microorganism culture in real-time. The microorganism culture from a microorganism production chamber is pumped to a flow chamber. Laser diodes emit light at certain wavelengths through the flow chamber, which is sensed by photodiodes. A laser control circuitry is operatively connected to the laser diodes and a signal conditioning circuitry is operatively connected to the photodiodes. A microprocessor reads and records voltage signals corresponding to the wavelengths. A data acquisition system converts said voltage signals into measurements of biological parameters, which are displayed on a graphical user interface and allow a user to monitor the measurements in real time.

47 OTHER INSTRUMENTATION↗