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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Development of a Kalman filter estimator for simulation and control of particulate matter distribution of a diesel catalyzed particulate filter

The knowledge of the temperature and particulate matter mass distribution is essential for monitoring the performance and durability of a catalyzed particulate filter. A catalyzed particulate filter model was developed, and it showed capability to accurately predict temperature and particulate matter mass distribution and pressure drop across the catalyzed particulate filter. However, the high-fidelity model is computationally demanding. Therefore, a reduced order multi-zone particulate filter model was developed to reduce computational complexity with an acceptable level of accuracy. In order to develop a reduced order model, a parametric study was carried out to determine the number of zones necessary for aftertreatment control applications. The catalyzed particulate filter model was further reduced by carrying out a sensitivity study of the selected model assumptions. The reduced order multi-zone particulate filter model with 5 × 5 zones was selected to develop a catalyzed particulate filter state estimator considering its computational time and accuracy. Next, a Kalman filter–based catalyzed particulate filter estimator was developed to estimate unknown states of the catalyzed particulate filter such as temperature and particulate matter mass distribution and pressure drop (Δ P) using the sensor inputs to the engine electronic control unit and the reduced order multi-zone particulate filter model. A diesel oxidation catalyst estimator was also integrated with the catalyzed particulate filter estimator in order to provide estimates of diesel oxidation catalyst outlet concentrations of NO 2 and hydrocarbons and inlet temperature for the catalyzed particulate filter estimator. The combined diesel oxidation catalyst–catalyzed particulate filter estimator was validated for an active regeneration experiment. The validation results for catalyzed particulate filter temperature distribution showed that the root mean square temperature error by using the diesel oxidation catalyst–catalyzed particulate filter estimator is within 3.2 °C compared to the experimental data. Similarly, the Δ P estimator closely simulated the measured total Δ P and the estimated cake pressure drop error is within 0.2 kPa compared to the high-fidelity catalyzed particulate filter model.

Engineering↗
DOE OSTI2015

Bowtie filters for dedicated breast CT: Analysis of bowtie filter material selection

Purpose: For a given bowtie filter design, both the selection of material and the physical design control the energy fluence, and consequently the dose distribution, in the object. Using three previously described bowtie filter designs, the goal of this work is to demonstrate the effect that different materials have on the bowtie filter performance measures. Methods: Three bowtie filter designs that compensate for one or more aspects of the beam-modifying effects due to the differences in path length in a projection have been designed. The nature of the designs allows for their realization using a variety of materials. The designs were based on a phantom, 14 cm in diameter, composed of 40% fibroglandular and 60% adipose tissue. Bowtie design #1 is based on single material spectral matching and produces nearly uniform spectral shape for radiation incident upon the detector. Bowtie design #2 uses the idea of basis-material decomposition to produce the same spectral shape and intensity at the detector, using two different materials. With bowtie design #3, it is possible to eliminate the beam hardening effect in the reconstructed image by adjusting the bowtie filter thickness so that the effective attenuation coefficient for every ray is the same. Seven different materials were chosen to represent a range of chemical compositions and densities. After calculation of construction parameters for each bowtie filter design, a bowtie filter was created using each of these materials (assuming reasonable construction parameters were obtained), resulting in a total of 26 bowtie filters modeled analytically and in the PENELOPE Monte Carlo simulation environment. Using the analytical model of each bowtie filter, design profiles were obtained and energy fluence as a function of fan-angle was calculated. Projection images with and without each bowtie filter design were also generated using PENELOPE and reconstructed using FBP. Parameters such as dose distribution, noise uniformity, and scatter were investigated. Results: Analytical calculations with and without each bowtie filter show that some materials for a given design produce bowtie filters that are too large for implementation in breast CT scanners or too small to accurately manufacture. Results also demonstrate the ability to manipulate the energy fluence distribution (dynamic range) by using different materials, or different combinations of materials, for a given bowtie filter design. This feature is especially advantageous when using photon counting detector technology. Monte Carlo simulation results from PENELOPE show that all studied material choices for bowtie design #2 achieve nearly uniform dose distribution, noise uniformity index less than 5%, and nearly uniform scatter-to-primary ratio. These same features can also be obtained using certain materials with bowtie designs #1 and #3. Conclusions: With the three bowtie filter designs used in this work, the selection of material is an important design consideration. An appropriate material choice can improve image quality, dose uniformity, and dynamic range.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Importance of filter’s microstructure in dynamic filtration modeling of gasoline particulate filters (GPFs): Inhomogeneous porosity and pore size distribution

The state-of-the-art multiscale modeling of GPFs including channel scale, wall scale, and pore scale is described. The microstructures of two GPFs were experimentally characterized. The pore size distributions of the GPFs were determined by mercury porosimetry. The porosity was measured by X-ray computed tomography (CT) and found to be inhomogeneous across the substrate wall. The significance of pore size distribution with respect to filtration performance was analyzed. The predictions of filtration efficiency were improved by including the pore size distribution in the filtration model. A dynamic heterogeneous multiscale filtration (HMF) model was utilized to simulate particulate filtration on a single channel particulate filter with realistic particulate emissions from a spark-ignition direct-injection (SIDI) gasoline engine. The dynamic evolution of filter’s microstructure and macroscopic filtration characteristics including mass- and number-based filtration efficiencies and pressure drop were predicted and discussed. The microstructure of the GPF substrate including inhomogeneous porosity and pore size distribution is found to significantly influence local particulate deposition inside the substrate and macroscopic filtration performance and is recommended to be resolved in the filtration model to simulate and evaluate the filtration performance of GPFs.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2015

Bowtie filters for dedicated breast CT: Theory and computational implementation

Purpose: To design bowtie filters with improved properties for dedicated breast CT to improve image quality and reduce dose to the patient. Methods: The authors present three different bowtie filters designed for a cylindrical 14-cm diameter phantom with a uniform composition of 40/60 breast tissue, which vary in their design objectives and performance improvements. Bowtie design #1 is based on single material spectral matching and produces nearly uniform spectral shape for radiation incident upon the detector. Bowtie design #2 uses the idea of basis material decomposition to produce the same spectral shape and intensity at the detector, using two different materials. Bowtie design #3 eliminates the beam hardening effect in the reconstructed image by adjusting the bowtie filter thickness so that the effective attenuation coefficient for every ray is the same. All three designs are obtained using analytical computational methods and linear attenuation coefficients. Thus, the designs do not take into account the effects of scatter. The authors considered this to be a reasonable approach to the filter design problem since the use of Monte Carlo methods would have been computationally intensive. The filter profiles for a cone-angle of 0° were used for the entire length of each filter because the differences between those profiles and the correct cone-beam profiles for the cone angles in our system are very small, and the constant profiles allowed construction of the filters with the facilities available to us. For evaluation of the filters, we used Monte Carlo simulation techniques and the full cone-beam geometry. Images were generated with and without each bowtie filter to analyze the effect on dose distribution, noise uniformity, and contrast-to-noise ratio (CNR) homogeneity. Line profiles through the reconstructed images generated from the simulated projection images were also used as validation for the filter designs. Results: Examples of the three designs are presented. Initial verification of performance of the designs was done using analytical computations of HVL, intensity, and effective attenuation coefficient behind the phantom as a function of fan-angle with a cone-angle of 0°. The performance of the designs depends only weakly on incident spectrum and tissue composition. For all designs, the dynamic range requirement on the detector was reduced compared to the no-bowtie-filter case. Further verification of the filter designs was achieved through analysis of reconstructed images from simulations. Simulation data also showed that the use of our bowtie filters can reduce peripheral dose to the breast by 61% and provide uniform noise and CNR distributions. The bowtie filter design concepts validated in this work were then used to create a computational realization of a 3D anthropomorphic bowtie filter capable of achieving a constant effective attenuation coefficient behind the entire field-of-view of an anthropomorphic breast phantom. Conclusions: Three different bowtie filter designs that vary in performance improvements were described and evaluated using computational and simulation techniques. Results indicate that the designs are robust against variations in breast diameter, breast composition, and tube voltage, and that the use of these filters can reduce patient dose and improve image quality compared to the no-bowtie-filter case.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

On-Board Particulate Filter Failure Prevention and Failure Diagnostics Using Radio Frequency Sensing

The increasing use of diesel and gasoline particulate filters requires advanced on-board diagnostics (OBD) to prevent and detect filter failures and malfunctions. Early detection of upstream (engine-out) malfunctions is paramount to preventing irreversible damage to downstream aftertreatment system components. Such early detection can mitigate the failure of the particulate filter resulting in the escape of emissions exceeding permissible limits and extend the component life. However, despite best efforts at early detection and filter failure prevention, the OBD system must also be able to detect filter failures when they occur. In this paper, radio frequency (RF) sensors were used to directly monitor the particulate filter state of health for both gasoline particulate filter (GPF) and diesel particulate filter (DPF) applications. The testing included controlled engine dynamometer evaluations, which characterized soot slip from various filter failure modes, as well as on-road fleet vehicle tests. The results show a high sensitivity to detect conditions resulting in soot leakage from the particulate filter, as well as potential for direct detection of structural failures including internal cracks and melted regions within the filter media itself. Finally and furthermore, the measurements demonstrate, for the first time, the capability to employ a direct and continuous monitor of particulate filter diagnostics to both prevent and detect potential failure conditions in the field.

42 ENGINEERING↗
DOE OSTI2019

Performance Evaluation of AG-1 FC Filters Under Upset Conditions and the Effects of Aging on Filters - 19501

High efficiency particulate air (HEPA) filters are routinely used in nearly every operating Department of Energy (DOE) and National Nuclear Safety Administration (NNSA) nuclear facility. These nuclear grade HEPA filters installed in DOE and NNSA confinement ventilation systems are credited as the final barrier to protect the environment, the public, and the worker from accidental release of virtually all airborne radioactive materials, and must meet the American Society of Mechanical Engineers' (ASME) Code on Nuclear Air and Gas Treatment (CONAGT) AG-1 standard. This testing activity evaluates ASME AG-1 Section FC axial flow HEPA filters, both separator and separator-less, under upset conditions. Additionally, testing efforts have analyzed the effects of filter degradation due to aging. In 1997, the Defense Nuclear Facilities Safety Board (DNFSB) raised concerns of the potential vulnerability of HEPA filters in vital safety systems, both from a design stand point and the potential for degradation of HEPA filter performance over time. The DOE Office of Environmental Management (DOE-EM) has a Cooperative Agreement with Mississippi State University (MSU) Institute for Clean Energy Technology (ICET) to conduct testing of HEPA filters. DOE-EM has established a Technical Working Group (TWG) of over thirty subject matter experts from the nuclear industry to provide input and oversight of ICET projects and activities. This has included establishment/approval of testing parameters for evaluating these filters under ASME NQA-1 compliant Test Plans. The current scope of work involves evaluation of the performance envelope for new and aged separator and separator-less designs of AG-1 Section FC axial flow HEPA filters. A range of elevated test conditions (T and RH) are used to determine the operating envelope within which DOE nuclear safety experts can credit installed HEPA filter performance, thereby establishing a risk-informed DOE service life. This paper will present preliminary test results of new and aged axial flow filters tested at ICET. Results in this paper include data collected from new separator and separator-less type FC HEPA filters and equivalent test data for a limited group of aged separator and separator-less type FC HEPA filters. Testing for both scopes of work evaluate initial filter performance under ambient conditions of temperature (60 deg. F - 80 deg. F (∼16 - ∼27 deg. C)) and relative humidity (40-60%), loading of each filter with Aluminum Trihydroxide, Al(OH)3, to a specified differential pressure, and then exposing the filter to specified elevated temperature and relative humidity conditions. In addition to the upset conditions of elevated temperature and relative humidity, the performance of HEPA filters under fire scenarios is not well characterized. ICET is currently designing a burn box and testing apparatus to study the effects of fire from burning liquids and a wide range of blends of combustible solids. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Stacked filters: learning to filter by structure

We present Stacked Filters, a new probabilistic filter which is fast and robust similar to query-agnostic filters (such as Bloom and Cuckoo filters), and at the same time brings low false positive rates and sizes similar to classifier-based filters (such as Learned Filters). The core idea is that Stacked Filters incorporate workload knowledge about frequently queried non-existing values. Instead of learning, they structurally incorporate that knowledge using hashing and several sequenced filter layers, indexing both data and frequent negatives. Stacked Filters can also gather workload knowledge on-the-fly and adaptively build the filter. We show experimentally that for a given memory budget, Stacked Filters achieve end-to-end query throughput up to 130x better than the best alternative for a workload, either query-agnostic or classifier-based filters, and depending on where data is (SSD or HDD).

Computer Science↗
DOE OSTI2019

Prototype Ceramic HEPA Filter Testing and Filter Media Research and Development for Nuclear Facility Ventilation

This is a brief summary of recent and past Ceramic HEPA Filter research and development activities under an NNSA NSR&D funded project and describes on-going plans for FY19 work as presently planned. Prior work has evaluated concepts for a ceramic HEPA filter including ceramic support materials, filter media including electrospun filter media, and metal housing designs to accommodate the conservative temperature performance target of up to 500°C. This has been supported by modelling efforts discussed with nuclear facility system engineers and their management. The temperature and time-attemperature are based on conservative, bounding temperatures from fire analysis presented as an EFCOG best practice paper for nuclear facility safety analysis. The overall goal is to improve safety of DOE nuclear facilities during fire scenarios by developing improved filtration technology including increasing temperature performance while maintaining acceptable filter pressure drop. Ceramic filtration technology can provide robust, passive mitigation against radiological releases. The goal of the ceramic HEPA filter is to provide a HEPA filter that provides increased temperature performance in an equivalent form factor (size and shape) that is similar to existing conventional HEPA filters used in facilities. Once development is complete and qualified for use in facilities, ceramic HEPA filters could simplify and reduce safety and support system costs, as well as lower life-cycle costs. Installation, monitoring, and maintenance of active fire suppression systems, as well as other related systems, are a considerable on-going cost to nuclear facilities. Reducing the level of dependence on Safety Class and Safety Significant fire alarm and fire suppression systems could allow significant cost savings. At present we are continuing research and development efforts towards the goal of a ceramic filter design, including improved ceramic filter media, that could reduce total operation cost for facilities utilizing HEPA filters.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Prototype Ceramic HEPA Filter Testing and Filter Media Research and Development for Nuclear Facility Ventilation

This is a brief summary of recent and past Ceramic HEPA Filter research and development activities under an NNSA NSR&D funded project and describes on-going plans for FY19 work as presently planned. Prior work has evaluated concepts for a ceramic HEPA filter including ceramic support materials, filter media including electrospun filter media, and metal housing designs to accommodate the conservative temperature performance target of up to 500°C. This has been supported by modelling efforts discussed with nuclear facility system engineers and their management. The temperature and time-at-temperature are based on conservative, bounding temperatures from fire analysis presented as an EFCOG best practice paper for nuclear facility safety analysis. The overall goal is to improve safety of DOE nuclear facilities during fire scenarios by developing improved filtration technology including increasing temperature performance while maintaining acceptable filter pressure drop. Ceramic filtration technology can provide robust, passive mitigation against radiological releases. The goal of the ceramic HEPA filter is to provide a HEPA filter that provides increased temperature performance in an equivalent form factor (size and shape) that is similar to existing conventional HEPA filters used in facilities. Once development is complete and qualified for use in facilities, ceramic HEPA filters could simplify and reduce safety and support system costs, as well as lower life-cycle costs. Installation, monitoring, and maintenance of active fire suppression systems, as well as other related systems, are a considerable on-going cost to nuclear facilities. Reducing the level of dependence on Safety Class and Safety Significant fire alarm and fire suppression systems could allow significant cost savings, while maintaining safety. At present we are continuing research and development efforts towards the goal of a ceramic filter design, including improved ceramic filter media, that could reduce total operation cost for facilities utilizing HEPA filters.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Prototype Ceramic High Efficiency Particulate Air Filter Testing and Filter Media Development for Nuclear Facility Ventilation

This report summarizes recent and past related Ceramic HEPA Filter activity for this NNSA NSR&D project and on-going plans for FY18 and FY19 work as presently planned. Prior work has evaluated concepts for a ceramic HEPA filter including ceramic support materials, filter media including electrospun filter media, and metal housing designs to accommodate the conservative temperature performance target of up to 500°C. This has been supported by modelling efforts discussed with nuclear facility system engineers and their management. The temperature and time-at-temperature are based on conservative, bounding temperatures from fire analysis presented as a draft EFCOG best practice paper for nuclear facility safety analysis. The overall goal is to improve safety of DOE nuclear facilities during fire scenarios by developing improved filtration technology including increasing performance while reducing pressure drop. Ceramic filtration technology can provide robust, passive mitigation against radiological releases. The goal of the ceramic HEPA filter is to provide a robust HEPA filter that provides increased temperature performance in an equivalent form factor (size and shape) that is similar to existing conventional HEPA filters used in facilities. Once qualified for use in facilities, the benefit of a ceramic HEPA filters could simplify and reduce safety and support system costs, as well as considerably lower life-cycle costs. Installation, monitoring, and maintenance of active fire suppression systems, as well as other related systems, are a considerable on-going cost to nuclear facilities. Reducing the level of dependence on Safety Class and Safety Significant fire alarm and fire suppression systems could allow significant cost savings. At present we are continuing research and development efforts towards the goal of a ceramic filter design, including improved ceramic filter media, that could reduce total operation cost for facilities utilizing HEPA filters.

42 ENGINEERING↗
DOE OSTI2022

The Simulation and Design of an On-Chip Superconducting Millimetre Filter-Bank Spectrometer

Abstract Superconducting on-chip filter banks provide a scalable, space saving solution to create imaging spectrometers at millimetre and submillimetre wavelengths. We present an easy to realise, lithographed superconducting filter design with a high tolerance to fabrication error. Using a capacitively coupled $$\lambda /2$$ λ / 2 microstrip resonator to define a narrow ( $$\lambda /\Delta \lambda = 300$$ λ / Δ λ = 300 ) spectral pass band, the filtered output of a given spectrometer channel directly connects to a lumped-element kinetic inductance detector. We show the tolerance analysis of our design, demonstrating $$<11\%$$ < 11 % change in filter quality factor to any one realistic fabrication error and a full filter-bank efficiency forecast to be 50% after accounting for fabrication errors and dielectric loss tangent.

Robson, G. (ORCID:0000000315279326)↗
DOE OSTI2014

Final Report: Part 1. In-Place Filter Testing Instrument for Nuclear Material Containers. Part 2. Canister Filter Test Standards for Aerosol Capture Rates.

A portable instrument has been developed to assess the functionality of filter sand o-rings on nuclear material storage canisters, without requiring removal of the canister lid. Additionally, a set of fifteen filter standards were procured for verifying aerosol leakage and pressure drop measurements in the Los Alamos Filter Test System. The US Department of Energy uses several thousand canisters for storing nuclear material in different chemical and physical forms. Specialized filters are installed into canister lids to allow gases to escape, and to maintain an internal ambient pressure while containing radioactive contaminants. Diagnosing the condition of container filters and canister integrity is important to ensure worker and public safety and for determining the handling requirements of legacy apparatus. This report describes the In-Place-Filter-Tester, the Instrument Development Plan and the Instrument Operating Method that were developed at the Los Alamos National Laboratory to determine the “as found” condition of unopened storage canisters. The Instrument Operating Method provides instructions for future evaluations of as-found canisters packaged with nuclear material. Customized stainless steel canister interfaces were developed for pressure-port access and to apply a suction clamping force for the interface. These are compatible with selected Hagan-style and SAVY-4000 storage canisters that were purchased from NFT (Nuclear Filter Technology, Golden, CO). Two instruments were developed for this effort: an initial Los Alamos POC (Proof-of-Concept) unit and the final Los Alamos IPFT system. The Los Alamos POC was used to create the Instrument Development Plan: (1) to determine the air flow and pressure characteristics associated with canister filter clogging, and (2) to test simulated configurations that mimicked canister leakage paths. The canister leakage scenarios included quantifying: (A) air leakage due to foreign material (i.e. dust and hair) fouling of o-rings, (B) leakage through simulated cracks in o-rings, and (C) air leakage due to inadequately tightened canister lids. The Los Alamos POC instrument determined pertinent air flow and pressure quantities, and this knowledge was used to specify a customized Isaac® (Z axis, Salt Lake City, UT) leak test module. The final Los Alamos IPFT (incorporating the Isaac® leak test module) was used to repeat the tests in the Instrument Development Plan (with simulated filter clogging tests and canister leak pathway tests). The Los Alamos IPFT instrument is capable of determining filter clogging and leak rate conditions, without requiring removal of the container lid. The IPFT measures pressure decay rate from 1.7E-03 in WC/sec to 1.7E-01 in WC/sec. On the same unit scale, helium leak testing of canisters has a range from 5.7E-07 in WC/sec to 1.9E-03 in WC/sec. For a 5-quart storage canister, the IPFT measures equivalent leak flow rates from 0.03 to 3.0 cc/sec. The IPFT does not provide the same sensitivity as helium leak testing, but is able to gauge the assembled condition of as-found and in-situ canisters.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2023

Spectral shaping of an ultrafast ytterbium fiber laser via a passive intracavity optical filter: a simple and reliable route to sub-45 fs pulses

We investigate the use of passive intracavity optical filters for controlling the laser output spectrum of a polarization-mode-locked, ultrafast ytterbium fiber laser. The overall lasing bandwidth is increased or extended by strategic choice of the filter cutoff frequency. Overall laser performance, including pulse compression and intensity noise, is investigated for both shortpass and longpass filters with a range of cutoff frequencies. The intracavity filter not only shapes the output spectra, but also provides a route for overall broader bandwidths and shorter pulses in ytterbium fiber lasers. These results demonstrate that spectral shaping with a passive filter is a useful tool to routinely achieve sub-45 fs pulse durations in ytterbium fiber lasers.

Cooper, Nicholas D.↗
DOE OSTI2021

Technical analysis of filter testing at the U.S. Department of Energy Filter Test Facility

The U.S. Department of Energy (DOE) technical standard DOE-STD-3020-2015 requires verification testing at the Filter Test Facility (FTF) of high-efficiency particulate air (HEPA) filters to be installed in nuclear facility (Hazard Category 1, 2, 3, and radiological facilities) confinement ventilation systems, or to be installed in habitability systems (e.g., filters for protection of workers required to act for the control and mitigation of emergency situations). Filters in these applications perform a safety function in accident situations, are designated as important to safety, or are necessary for habitability systems. Different FTFs have operated for decades, and results of tests are available to examine the need for and benefits of continued execution of 100 percent QA verification testing. The objective of this study and resulting report was to assess the need for 100 percent QA testing at the current FTF in Maryland, based on an examination of a database of test results from 2013 to August 2020. Filters that require independent testing per DOE-STD-3020-2015 to be installed in nuclear facilities are sent to the FTF before being shipped to the facilities. The FTF examines the documentation (e.g., certificates of compliance, results of particle penetration and airflow resistance testing by the manufacturers, labels affixed to filters and packages, and other requirements specified in purchase orders by the nuclear facility operators), implements visual inspections of the physical state of the filters, and checks the dimensions of frames. Filters that meet the documentation and visual inspection requirements are subjected to particle penetration and airflow resistance testing. In case of rejections, the filters are shipped back to the manufacturers, at the cost of the manufacturers, for replacement. Filters that pass all tests are shipped to the nuclear facilities.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Impact of Irradiation-Induced Filter Heating on Calibration of NIR-Longpass-Filtered Reference Solar Cells

Reference solar cells play a crucial role in determining the performance of photovoltaic (PV) devices. In the performance calibration chain of mainstream single-junction PV technologies, common reference cell types include Si, KG-filtered Si, and GaAs cells. For emerging multijunction (MJ) PV technologies, such as CdTe/Si and perovskite/Si, Si reference cells with colored glass near-infrared-longpass (LP) filters like Schott RG-715 and 850 glass have been proposed. They offer a better spectral response that matches the bottom junctions of the emerging MJs, which could lead to lower uncertainties in performance measurements. However, this article reveals a prominent decrease in short-circuit current (ISC) during National Renewable Energy Laboratory's primary calibration over the course of minutes when using this type of LP-filtered reference cell, which could result in unacceptable measurement errors. Unlike quartz or KG filter glasses, LP colored glass filters demonstrate temperature-sensitive cut-on wavelength. When incident irradiance reaches these LP-filtered reference cells, the increased temperature due to light absorption causes a shift of the cut-on to longer wavelength. As a result, the device I SC exhibits a continuous decrease (approximately a 2.5% drop with RG850 LP filter in a 5-min duration) even when the device temperature is controlled at 25 degrees C. To address the temperature gradient issue between colored glass LP filter and the reference cell, we propose the direct integration of thin-film LP semiconductor layer on reference cells. This type of LP-filter-integrated cell has shown minimal temperature-related I SC variation and can serve as a more reliable reference cell source for accurate performance measurements.

14 SOLAR ENERGY↗
DOE OSTI2014

Method for reducing pressure drop through filters, and filter exhibiting reduced pressure drop

Methods for generating and applying coatings to filters with porous material in order to reduce large pressure drop increases as material accumulates in a filter, as well as the filter exhibiting reduced and/or more uniform pressure drop. The filter can be a diesel particulate trap for removing particulate matter such as soot from the exhaust of a diesel engine. Porous material such as ash is loaded on the surface of the substrate or filter walls, such as by coating, depositing, distributing or layering the porous material along the channel walls of the filter in an amount effective for minimizing or preventing depth filtration during use of the filter. Efficient filtration at acceptable flow rates is achieved.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Calibration of scintillation-light filters for neutron time-of-flight spectrometers at the National Ignition Facility

Sixty-four neutral density filters constructed of metal plates with 88 apertures of varying diameter have been radiographed with a soft x-ray source and CCD camera at National Security Technologies, Livermore. An analysis of the radiographs fits the radial dependence of the apertures’ image intensities to sigmoid functions, which can describe the rapidly decreasing intensity towards the apertures’ edges. The fitted image intensities determine the relative attenuation value of each filter. Absolute attenuation values of several imaged filters, measured in situ during calibration experiments, normalize the relative quantities which are now used in analyses of neutron spectrometer data at the National Ignition Facility.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗