SEARCH · Engineering Papers
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Many next generation remote sensing systems plan to use solar reflecting, diffuse standards to calibrate their sensors in-flight. As these diffusers are subject to UV degradation and contamination.
Purpose: Report on implementation of a Virtual EPID Standard Phantom Audit (VESPA) for IMRT to support credentialing of facilities for clinical trials. Data is acquired by local facility staff and transferred electronically. Analysis is performed centrally. Methods: VESPA is based on published methods and a clinically established IMRT QA procedure, here extended to multi-vendor equipment. Facilities, provided with web-based comprehensive instructions and CT datasets, create IMRT treatment plans. They deliver the treatments directly to their EPID without phantom or couch in the beam. They also deliver a set of simple calibration fields. Collected EPID images are uploaded electronically. In the analysis, the dose is projected back into a virtual phantom and 3D gamma analysis is performed. 2D dose planes and linear dose profiles can be analysed when needed for clarification. Results: Pilot facilities covering a range of planning and delivery systems have performed data acquisition and upload successfully. Analysis showed agreement comparable to local experience with the method. Advantages of VESPA are (1) fast turnaround mainly driven by the facility’s capability to provide the requested EPID images, (2) the possibility for facilities performing the audit in parallel, as there is no need to wait for a phantom, (3) simple and efficient credentialing for international facilities, (4) a large set of data points, and (5) a reduced impact on resources and environment as there is no need to transport heavy phantoms or audit staff. Limitations of the current implementation of VESPA for trials credentialing are that it does not provide absolute dosimetry, therefore a Level 1 audit still required, and that it relies on correctly delivered open calibration fields, which are used for system calibration. Conclusion: The implemented EPID based IMRT audit system promises to dramatically improve credentialing efficiency for clinical trials and wider applications. VESPA for VMAT will follow soon.
Purpose: Cardiac x-ray detectors are used to acquire moving images in real-time for angiography and interventional procedures. Detective quantum efficiency (DQE) is not generally measured on these dynamic detectors; the required “for processing” image data and control of x-ray settings have not been accessible. By 2016, USA hospital physicists will have the ability to measure DQE and will likely utilize the International Electrotechnical Commission (IEC) standard for measuring DQE of dynamic x-ray imaging devices. The current IEC standard requires an image of a tilted tungsten edge test object to obtain modulation transfer function (MTF) for DQE calculation. It specifies the range of edge angles to use; however, it does not specify a preferred method to determine this angle for image analysis. The study aimed to answer the question “will my choice in method impact my results?” Four different established edge angle determination methods were compared to investigate the impact on DQE. Methods: Following the IEC standard, edge and flat field images were acquired on a cardiac flat-panel detector to calculate MTF and noise power spectrum, respectively, to determine DQE. Accuracy of the methods in determining the correct angle was ascertained using a simulated edge image with known angulations. Precision of the methods was ascertained using variability of MTF and DQE, calculated via bootstrapping. Results: Three methods provided near equal angles and the same MTF while the fourth, with an angular difference of 6%, had a MTF lower by 3% at 1.5 mm{sup −1} spatial frequency and 8% at 2.5 mm{sup −1}; corresponding DQE differences were 6% at 1.5 mm{sup −1} and 17% at 2.5 mm{sup −1}; differences were greater than standard deviations in the measurements. Conclusions: DQE measurements may vary by a significant amount, depending on the method used to determine the edge angle when following the IEC standard methodology for a cardiac x-ray detector. The most accurate and precise methods are recommended for absolute assessments and reproducible measurements, respectively.
If a terrorist nuclear explosion were to occur in the United States, high-quality (accurate and precise) legally defensible nuclear forensics measurements will be required to assure the certainty and confidence needed, for conclusions drawn from these data will be coupled with law enforcement and intelligence information for the purposes of attribution and retribution. Standard Reference Materials (SRMs)/Certified Reference Materials (CRMs) establish the traceability, accuracy, and precision of nuclear forensic measurements and provide the ability to benchmark measurement methods essential to meeting the requirements of legal scrutiny. Currently there is a critical shortage of key SRMs/CRMs required for accurate and precise measurements that are fundamental to nuclear measurements supporting pre- and post-detonation nuclear forensics. Supplies either do not exist, are not good enough, are in short supply, and/or are very expensive. The radionuclide measurement techniques and data quality objectives for pre- and post-detonation nuclear forensics are quite different than the applications for which the current suite of available SRMs/CRMs was developed. Specifically, 1) modern mass spectrometry methods have largely replaced traditional activity-based measurement methods for quantifying small quantities of long-lived radionuclides and most trace radionuclide SRMs/CRMs are certified for activity and are thus not adequate for current applications, 2) modern instrumental methods are capable of higher precision than historic measurement techniques, and in some cases exceed the precision of the available SRMs/CRMs, and 3) the quality assurance requirements for pre- and post-detonation nuclear forensics are such that the existing cadre of SRMs/CRMs does not adequately support the needs for method validation. There are numerous governmental stakeholders both within the US (DOE, DoD) and internationally (IAEA, JRC-ITU) whose missions are either directly involved with nuclear forensics measurements or rely on the forensic data obtained to make the exacting policy decisions (DOJ (FBI), DHS, CIA, DIA, DoD) associated with disrupting the production of illicit nuclear materials, interdicted nuclear materials or a nuclear/radiological detonation event. Starting in 2008 the DHS NTNFC, in collaboration with NBL and NIST, took on the production of suitable SRMs/CRMs for the pre-detonation nuclear forensics community. Two CRMs have been released since the start of this effort and two more are slated for completion in 2016. More recently, NIST, as a part of its mission as the US National Metrology Institute (NMI) to deliver standards (providing traceability) and foster homeland security, has launched the first certification campaign of a measurement traceable post nuclear detonation SRM. NIST, in cooperation with partner labs (AFIT (DoD), FBI (DOJ), and NPL) and with support from the FBI, has developed two Surrogate Post-Detonation Urban Debris (SPUD) Standard Reference Materials (SRMs) - SRM 4600 and 4601. These SRMs have been developed to simulate the expected debris mixture from the detonation of an Improvised Nuclear Device (IND) in an urban environment, which is capable of producing fresh fission as well as activation products. The elemental composition of the vitrified debris materials is a composite of minerals and metals characteristic of the concrete and steel, the building materials that would be exposed to a nuclear detonation and whose resulting activation products would be found in rubble samples collected for forensics evidence and attribution. Additionally, because post-detonation samples would also contain short-lived fission products, the debris materials have been doped with Uranium (U). To create the nuclear fission products, samples of the SPUD materials can be placed in a well-characterized nuclear reactor and exposed to a set neutron flux and energy, causing the encased U atoms to split and yield short-lived fission products. Because a known amount of U is added to the SPUD materials it is feasible to determine the concentration of the resulting fission products. The subsequent irradiated SPUD glass would be chemically similar to samples that would be generated in an actual detonation, and thus can serve as a standardized reference material for nuclear forensic post detonation measurements. (authors)
The Department of Energy s (DOE) Manufacturing Demonstration Facility (MDF) at Oak Ridge National Laboratory (ORNL) provides world-leading capabilities in advanced manufacturing (AM) facilities which leverage previous, on-going government investments in materials science research and characterization. MDF contains systems for fabricating components with complex geometries using AM techniques (i.e. 3D-Printing). Various metal alloy printers, for example, use electron beam melting (EBM) systems for creating these components which are otherwise extremely difficult- if not impossible- to machine. ORNL has partnered with manufacturers on improving the final part quality of components and developing new materials for further advancing these devices. One method being used to study (AM) processes in more depth relies on the advanced imaging capabilities at ORNL. High performance mid-wave infrared (IR) cameras are used for in-situ process monitoring and temperature measurements. However, standard factory calibrations are insufficient due to very low transmissions of the leaded glass window required for X-ray absorption. Two techniques for temperature calibrations will be presented and compared. In-situ measurement of emittance will also be discussed. Ample information can be learned from in-situ IR process monitoring of the EBM process. Ultimately, these imaging systems have the potential for routine use for online quality assurance and feedback control.
Characterization of the Radiation Calibration and Spectroscopy Laboratory (RCS) Co-60 source radiation pool was successfully completed. The characterization was done by performing several measurements of dose rate in the center of the Co-60 source radiation pool and at multiple heights from the bottom of the pool. The measurements were taken between November 2018 through January 2019. Opti-Chromic FWT-70-40M dosimeters were used for this measurement. A 7.3 cm inner diameter stainless steel cylinder (vessel) was used to lower the dosimeters to the bottom of the pool inside the 16 cm dimeter Co-60 source basket. The dose rate was measured at heights of 5.5, 12, 19, and 23 cm from the bottom of the pool. The report “Tour of the Standards and Calibration Laboratory” includes information about the Co-60 source radiation pool. The importance of performing the Co-60 source characterization is to confirm previously reported Co-60 source dose rate measurements and to provide a documented measuring procedure for researchers and others who want to use the Co-60 source to evaluate the effects of radiation on space-based equipment for other applications. The measured dose rate at the abovementioned heights was 0.65, 0.69, 0.53, 0.23 krad/min respectively with the highest coefficient of variation of less than 10%.
The CUP-2 uranium ore concentrate (UOC) standard reference material, a powder, was produced at the Blind River uranium refinery of Eldorado Resources Ltd. in Canada in 1986. This material was produced as part of a joint effort by the Canadian Certified Reference Materials Project and the Canadian Uranium Producers Metallurgical Committee to develop a certified reference material for uranium concentration and the concentration of several impurity constituents. This standard was developed to satisfy the requirements of the UOC mining and milling industry, and was characterized with this purpose in mind. To produce CUP-2, approximately 25 kg of UOC derived from the Blind River uranium refinery was blended, homogenized, and assessed for homogeneity by X-ray fluorescence (XRF) analysis. The homogenized material was then packaged into bottles, containing 50 g of material each, and distributed for analysis to laboratories in 1986. The CUP-2 UOC standard was characterized by an interlaboratory analysis program involving eight member laboratories, six commercial laboratories, and three additional volunteer laboratories. Each laboratory provided five replicate results on up to 17 analytes, including total uranium concentration, and moisture content. The selection of analytical technique was left to each participating laboratory. Uranium was reported on an “as-received” basis; all other analytes (besides moisture content) were reported on a “dry-weight” basis. A bottle of 25g of CUP-2 UOC standard as described above was purchased by LLNL and characterized by the LLNL Nuclear Forensics Group. Non-destructive and destructive analytical techniques were applied to the UOC sample. Information obtained from short-term techniques such as photography, gamma spectrometry, and scanning electron microscopy were used to guide the performance of longer-term techniques such as ICP-MS. Some techniques, such as XRF and ICP-MS, provided complementary types of data. The results indicate that the CUP-2 standard has a natural isotopic ratio, and does not appear to have been isotopically enriched or depleted in any way, and was not contaminated by a source of uranium with a non-natural isotopic composition. Furthermore, the lack of 233 U and 236 U above the instrumental detection limit indicates that this sample was not exposed to a neutron flux, which would have generated one or both of these isotopes in measurable concentrations.
The NASA Metrology Information System (NMIS) was developed as a subsystem of the NASA Equipment Management System (NEMS) to provide a standardized technique in managing the calibration programs of its field Centers and facilities. The NMIS is a computerized data-base system providing: automatic instrument calibration recall and control, historical data including calibration and repair labor and parts costs, incoming instrument performance condition; instrument data including description, manufacturer, model and serial number, and instrument user name location. NMIS automatically provides 28 standardized calibration system performance reports on a user selected schedule. An ad hoc report generation capability is also provided. A standardized form, the Metrology Control Document, was developed for use as a calibration work order and data input document. System implementation plan is presented.
The DHS TC Standards and the consensus ANSI Standards use 252 Cf as the neutron source for performance testing because its energy spectrum is similar to the 235 U and 239 Pu fission sources used in nuclear weapons. An emission rate of 20,000 ± 20% neutrons per second is used for testing of the radiological requirements both in the ANSI standards and the TCS. Determination of the accurate neutron emission rate of the test source is important for maintaining consistency and agreement between testing results obtained at different testing facilities. Several characteristics in the manufacture and the decay of the source need to be understood and accounted for in order to make an accurate measurement of the performance of the neutron detection instrument. Additionally, neutron response characteristics of the particular instrument need to be known and taken into account as well as neutron scattering in the testing environment.
Traditionally, the method used for measuring the isotope ratios is the Isotope Ratio Mass Spectrometers (IRMS). A new method has been used to determine the isotopic abundances, the Cavity Ring-Down Spectroscopy (CRDS). It consists of a technique of direct absorption, of high sensitivity, which is based on measuring the absorption ratio, as a function of time, of the light confined in a high finesse optical cavity, instead of the magnitude of light beam absorption. The values of {sup 18}O/{sup 16}O and D/H ratios are determined with respect to international standards VSMOW, GISP and SLAP from the International Atomic Energy Agency (IAEA). In this work, the IRMS and CRDS techniques are compared, verifying that the CRDS technique is promising and has some advantages compared to IRMS. It uses a smaller amount of sample, the isotope measurements are made simultaneously from the steam, reducing the analysis time. It also shows good reproducibility and accuracy, and it does not require a preliminary sample preparation.
In the event of an unattributed nuclear explosion, rapid assessment of the short-lived uranium isotope activity and mass can provide valuable information for subsequent forensic analysis. Rapid analysis in the field is enabled by using microfluidic chemistry and deployable instrumentation. Here, this work presents a flow chemistry system, controlled in LabVIEW, that integrates three functionalities: (1) selective extraction of uranium from the sample matrix via a 3D-printed supported liquid membrane module; (2) UV–visible absorbance spectrophotometry to measure the total uranium concentration in the strip flow; and (3) a portable CdTe γ-ray spectrometer coupled to a 3D-printed flow cell to measure 237 U activity concentration in the strip solution. The system was calibrated using standard solutions, and its functionality was demonstrated using a solution of depleted uranium spiked with 237 U. Uranium concentrations of 40–5000 μg/mL were directly quantified online using a 100 mm optical flow cell, while concentrations of 0.5–10 μg/mL were quantified online using a colorimetric reagent. The mass concentration measurement takes approximately 60 min while the activity concentration via γ-ray spectrometry varies depending on the activity of 237 U, with 1 kBq/mL requiring about 30 min of acquisition time to obtain <10% uncertainty at 1σ. This platform provides a fieldable approach for quantifying uranium mass and radioactivity relevant to postdetonation nuclear debris.
We investigated the role of femtosecond (fs) laser wavelength on laser ablation (LA) and its relation to laser generated aerosol counts and particle distribution, inductively coupled plasma-mass spectrometry (ICP-MS) signal intensity, detection limits, and elemental fractionation. Four different NIST standard reference materials (610, 613, 615, and 616) were ablated using 400 nm and 800 nm fs laser pulses to study the effect of wavelength on laser ablation rate, accuracy, precision, and fractionation. Our results show that the detection limits are lower for 400 nm laser excitation than 800 nm laser excitation at lower laser energies but approximately equal at higher energies. Ablation threshold was also found to be lower for 400 nm than 800 nm laser excitation. Particle size distributions are very similar for 400 nm and 800 nm wavelengths; however, they differ significantly in counts at similar laser fluence levels. This study concludes that 400 nm LA is more beneficial for sample introduction in ICP-MS, particularly when lower laser energies are to be used for ablation.
Highlights: • New method for the analysis of 25-hydroxyvitamin D{sub 3} exploiting Girard P derivatisation. • Method also applicable to vitamin D{sub 3}, 1α,25- and 24,25-dihydroxyvitamin D{sub 3}. • By modification of the method 3-epi-25-hydroxyvitamin D{sub 3} can also be analysed. - Abstract: The total serum concentration of 25-hydroxyvitamins D (25-hydroxyvitamin D{sub 3} and 25-hydroxyvitamin D{sub 2}) is currently used as an indicator of vitamins D status. Vitamins D insufficiency is claimed to be associated with multiple diseases, thus accurate and precise reference methods for the quantification of 25-hydroxyvitamins D are needed. Here we present a novel enzyme-assisted derivatisation method for the analysis of vitamins D metabolites in adult serum utilising 25-[26,26,26,27,27,27-{sup 2}H{sub 6}]hydroxyvitamin D{sub 3} as the internal standard. Extraction of 25-hydroxyvitamins D from serum is performed with acetonitrile, which is shown to be more efficient than ethanol. Cholesterol oxidase is used to oxidize the 3β-hydroxy group in the vitamins D metabolites followed by derivatisation of the newly formed 3-oxo group with Girard P reagent. 17β-Hydroxysteroid dehydrogenase type 10 is shown to oxidize selectively the 3α-hydroxy group in the 3α-hydroxy epimer of 25-hydroxyvitamin D{sub 3}. Quantification is achieved by isotope-dilution liquid chromatography–tandem mass spectrometry. Recovery experiments for 25-hydroxyvitamin D{sub 3} performed on adult human serum give recovery of 102–106%. Furthermore in addition to 25-hydroxyvitamin D{sub 3}, 24,25-dihydroxyvitamin D{sub 3} and other uncharacterised dihydroxy metabolites, were detected in adult human serum.
The influence of thermal effects is a major uncertainty contribution to the calibration of Standard Platinum Resistance Thermometers (SPRTs) in fixed-point cells. Axial heat losses strongly depend on the fixed-point temperature, constructional details of cells and SPRTs and the resulting heat transfer between cell, thermometer, furnace and environment. At the zinc point contributions by heat conduction and thermal radiation must be considered. Although the measurement of temperature gradients in the re-entrant well of a fixed-point cell provides very important information about the influence of axial heat losses, further investigations are required for a reliable estimate of the resulting uncertainty contribution. It is shown that specific modifications of a zinc fixed-point cell, following generally accepted principles, may result in systematic deviations of the measured fixed-point temperatures larger than typically stated in the uncertainty budget of National Metrology Institutes (NMIs). The underlying heat transport processes are investigated and the consequences for the construction of zinc cells are discussed.
Neutron Activation Analysis (NAA) had been established in Nuclear Malaysia since 1980s. Most of the procedures established were done manually including sample registration. The samples were recorded manually in a logbook and given ID number. Then all samples, standards, SRM and blank were recorded on the irradiation vial and several forms prior to irradiation. These manual procedures carried out by the NAA laboratory personnel were time consuming and not efficient. Sample registration software is developed as part of IAEA/CRP project on ‘Development of Process Automation in the Neutron Activation Analysis (NAA) Facility in Malaysia Nuclear Agency (RC17399)’. The objective of the project is to create a pc-based data entry software during sample preparation stage. This is an effective method to replace redundant manual data entries that needs to be completed by laboratory personnel. The software developed will automatically generate sample code for each sample in one batch, create printable registration forms for administration purpose, and store selected parameters that will be passed to sample analysis program. The software is developed by using National Instruments Labview 8.6.
Purpose: The trend towards more SBRT treatments with fewer high dose fractions places increased importance on daily QA. Patient plan specific QA with 3%/3mm gamma analysis and daily output constancy checks may not be enough to guarantee the level of accuracy required for SBRT treatments. But increasing the already extensive amount of QA procedures that are required is a daunting proposition. We performed a feasibility study for more comprehensive automated daily QA that could improve the diagnostic capabilities of QA without increasing workload. Methods: We performed the study on a Siemens Artiste linear accelerator using the integrated flat panel EPID. We included square fields, a picket fence, overlap and representative IMRT fields to measure output, flatness, symmetry, beam center, and percent difference from the standard. We also imposed a set of machine errors: MLC leaf position, machine output, and beam steering to compare with the standard. Results: Daily output was consistent within +/− 1%. Change in steering current by 1.4% and 2.4% resulted in a 3.2% and 6.3% change in flatness. 1 and 2mm MLC leaf offset errors were visibly obvious in difference plots, but passed a 3%/3mm gamma analysis. A simple test of transmission in a picket fence can catch a leaf offset error of a single leaf by 1mm. The entire morning QA sequence is performed in less than 30 minutes and images are automatically analyzed. Conclusion: Automated QA procedures could be used to provide more comprehensive information about the machine with less time and human involvement. We have also shown that other simple tests are better able to catch MLC leaf position errors than a 3%/3mm gamma analysis commonly used for IMRT and modulated arc treatments. Finally, this information could be used to watch trends of the machine and predict problems before they lead to costly machine downtime.
Purpose: To develop a simple technique for testing display monitors for compliance with the DICOM Grayscale Standard Display Function (GSDF), in accordance with the recommendations of AAPM Task Group 18. Methods: We have developed a spreadsheet that can be used to compare both the luminance response and contrast response of a display to the GSDF, using luminance measurements of the SMPTE test pattern. The contrast response compares the slope of the GSDF j-index as a function of pixel value to that of the GSDF function, and should lie within the range 0.85 to 1.15. Results: We present the results of measurements both of primary diagnostic displays and of ultrasound and acquisition workstations, all at a tertiary care hospital. The Barco displays in the radiographic reading rooms are GSDF compliant or nearly so, while those in the ultrasound reading rooms and at the acquisition workstations generally show significantly higher contrast at low luminance levels than they would if GSDF compliant, and lower contrast at high luminance levels. Conclusion: The spreadsheet that we developed allows a simple comparison of measured display contrast response to the GSDF. Although we used the SMPTE pattern, the same technique could be used with other grayscale patterns, such as TG18-QC and TG18-PQC.
Purpose: To calculate the output factor of irregular shape electron beam at extended SSD using modified lateral build-up-ratio method. Methods: Circular cutouts from 2.0cm diameter to maximum possible sizes were prepared for applicator cone size of 15×15cm. In addition, different irregular cutouts were prepared. Percentage depth dose (PDD) curves were measured for each cutout using 6, 9, 12 and 16-MeV at the standard SSD of 100cm. The scanning was done using Multidata system and Scanditronix diodes on 2100SC Varian LINAC. In addition, for each cutout and electron beam energy doses were measured at SSD values of 100, 105, 110, 115cm using EDR2 films and diodes. Results: The measured PDD were normalized to the depth of 1.0mm. The lateral build-up-ratio (LBR) and the lateral scatter parameter (sigma) were calculated for each circular cutout using the open 15X15-cm2 field as the reference field. Taking the linear increase of sigma with cutout size into account, PDD of the irregular cutouts were calculated at 100 cm SSD. Furthermore, using the dose measured at different SSDs, the effective SSD value for each circular cutout and electron beam energy was determined. Employing the LBR and the effective-SSD values of the circular cutouts along with the calculated PDD of the irregular cutouts, the output factors of the irregular cutout at different extended SSD values were calculated. Finally, the calculated output factors were compared with the measured values. Conclusion: In this research, it is shown that output factor of irregular shape electron beam at extended SSD can be determined by using the LBR and the effective SSD values of circular cutouts. The percentage difference of the calculated output factor from the measured output factor for irregular cutouts at extended SSD were within 3.0%.