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Edge Zonal Flows and Blob Propagation in Alcator C-Mod

Description: Here we describe recent measurements of the 2-D motion of turbulence in the edge and scrape-off layer (SOL) of the Alcator C-Mod tokamak. This data was taken using the outer midplane gas puff imaging (GPI) camera, which views a 6 cm radial by 6 cm poloidal region near the separatrix just below the outer midplane [1]. The data were taken in Ohmic or RF heated L-mode plasmas at 400,000 frames/sec for {approx}50 msec/shot using a Phantom 710 camera in a 64 x 64 pixel format. The resulting 2-D vs. time movies [2] can resolve the structure and motion of the turbulence on a spatial scale covering 0.3-6 cm. The images were analyzed using either a 2-D cross-correlation code (Sec. 2) or a 2-D blob tracking code (Sec. 3).
Date: July 25, 2011
Creator: Zweben, S; Agostini, M; Davis, B; Grulke, O; Hager, R; Hughes, J et al.
Partner: UNT Libraries Government Documents Department

SQUID-Detected Microtesla MRI in the presence of Metal

Description: In magnetic resonance imaging (MRI) performed at fields of 1 T and above, the presence of a metal insert can distort the image because of susceptibility differences within the sample and modification of the radiofrequency fields by screening currents. Furthermore, it is not feasible to perform nuclear magnetic resonance (NMR) spectroscopy or acquire a magnetic resonance image if the sample is enclosed in a metal container. Both problems can be overcome by substantially lowering the NMR frequency. Using a microtesla imaging system operating at 2.8 kHz, with a superconducting quantum interference device (SQUID) as the signal detector, we have obtained distortion-free images of a phantom containing a titanium bar and three-dimensional images of an object enclosed in an aluminum can; in both cases high-field images are inaccessible.
Date: September 6, 2006
Creator: Moessle, Michael; Han, Song-I.; Myers, Whittier; Lee, Seung-Kyun; Kelso, Nathan; Hatridge, Michael et al.
Partner: UNT Libraries Government Documents Department

Influence of Manufacturing Processes on the Performance of Phantom Lungs

Description: Chest counting is an important tool for estimating the radiation dose to individuals who have inhaled radioactive materials. Chest counting systems are calibrated by counting the activity in the lungs of phantoms where the activity in the phantom lungs is known. In the United States a commonly used calibration phantom was developed at the Lawrence Livermore National Laboratory and is referred to as the Livermore Torso Phantom. An important feature of this phantom is that the phantom lungs can be interchanged so that the counting system can be challenged by different combinations of radionuclides and activity. Phantom lungs are made from lung tissue substitutes whose constituents are foaming plastics and various adjuvants selected to make the lung tissue substitute similar to normal healthy lung tissue. Some of the properties of phantom lungs cannot be readily controlled by phantom lung manufacturers. Some, such as density, are a complex function of the manufacturing process, while others, such as elemental composition of the bulk plastic are controlled by the plastics manufacturer without input, or knowledge of the phantom manufacturer. Despite the fact that some of these items cannot be controlled, they can be measured and accounted for. This report describes how manufacturing processes can influence the performance of phantom lungs. It is proposed that a metric that describes the brightness of the lung be employed by the phantom lung manufacturer to determine how well the phantom lung approximates the characteristics of a human lung. For many purposes, the linear attenuation of the lung tissue substitute is an appropriate surrogate for the brightness.
Date: October 1, 2008
Creator: Traub, Richard J.
Partner: UNT Libraries Government Documents Department

Final Scientific/Technical Report

Description: Boeing Phantom Works and its team originally proposed a three-year Phase III SPI project to develop a 30-kWh flywheel with a 100 kW power capability as a power risk management system (RMS) for power users and providers. The chief objectives for the Risk Management System Flywheel were to (1) demonstrate its ability to protect a critical load such as a small data center from swings in power availability, cost, and power factor and (2) show that the RMS flywheel can perform these functions with reduced noise, emissions, and operating costs when compared with non-HTS competitors including batteries, diesel generators, and microturbines.
Date: June 29, 2007
Creator: Strasik, Dr. Michael
Partner: UNT Libraries Government Documents Department

Sandia National Laboratories results for the 2010 criticality accident dosimetry exercise, at the CALIBAN reactor, CEA Valduc France.

Description: This document describes the personal nuclear accident dosimeter (PNAD) used by Sandia National Laboratories (SNL) and presents PNAD dosimetry results obtained during the Nuclear Accident Dosimeter Intercomparison Study held 20-23 September, 2010, at CEA Valduc, France. SNL PNADs were exposed in two separate irradiations from the CALIBAN reactor. Biases for reported neutron doses ranged from -15% to +0.4% with an average bias of -7.7%. PNADs were also exposed on the back side of phantoms to assess orientation effects.
Date: September 1, 2011
Creator: Ward, Dann C.
Partner: UNT Libraries Government Documents Department

Microwave Hematoma Detector for the Rapid Assessment of Head Injuries

Description: A non-invasive microwave device for the detection of epi/subdural hemorrhaging (hematoma) is under current development. The final device will be highly portable and allow real time assessment of head injuries, thereby satisfying early detection needs of the field technician as well as providing a tool for repetitious monitoring of high-risk individuals. The device will adopt the advanced technology of micropower impulse radar (MIR) which is a state of the art low cost ultra wide band (UWB) microwave radar developed here at LLNL. It will consist of a MIR transmitting and receiving module, a computer based signal processing module, and a device-to-patient signal coupling module--the UWB antenna. The prototype design is being guided by the needs of the patient and the practitioner along with the prerequisites of the technology including issues such as the specificity of the device, efficacy of diagnosis, accuracy, robustness, and patient comfort. The prototype development follows a concurrent approach which .includes experiments designed to evaluate requirements of the radar and antenna design, phantom development to facilitate laboratory investigations, and investigation into the limits of adapting pre-existing non-medical MIR devices to medical applications. This report will present the accomplishments and project highlights to date in the fiscal year 1999. Future project projections will also be discussed.
Date: February 11, 2000
Creator: Hadded, W.; Chang, J.; Rosenbury, T.; Dallum, G.; Welsch, P.; Scott, D. et al.
Partner: UNT Libraries Government Documents Department

An in-phantom comparison of neutron fields for BNCT

Description: Previously, the authors have developed the in-phantom neutron field assessment parameters T and D (Tumor) for the evaluation of epithermal neutron fields for use in BNCT. These parameters are based on an energy-spectrum-dependent neutron normal-tissue RBE and the treatment planning methodology of Gahbauer and his co-workers, which includes the effects of dose fractionation. In this paper, these neutron field assessment parameters were applied to The Ohio State University (OSU) design of an Accelerator Based Neutron Source (ABNS) (hereafter called the OSU-ABNS) and the Brookhaven Medical Research Reactor (BMRR) epithermal neutron beam (hereafter called the BMRR-ENB), in order to judge the suitability of the OSU-ABNS for BNCT. The BMRR-ENB was chosen as the basis for comparison because it is presently being used in human clinical trials of BNCT and because it is the standard to which other neutron beams are most often compared.
Date: January 1, 1998
Creator: Woollard, J.E.; Blue, T.E. & Capala, J.
Partner: UNT Libraries Government Documents Department

First Results for a Novel Superconducting Imaging-Surface Sensor Array

Description: A superconducting imaging-surface system was constructed using 12 coplanar thin-film SQUID magnetometers located parallel to and spaced 2 cm from a 25 cm diameter lead imaging-plane. Some measurements included two additional sensors on the ''back'' side of the superconducting imaging-plane to study the field symmetry for our system. Performance was measured in a shielded can and in the open laboratory environment. Data from this system has been used to: (a) understand the noise characteristics of the dewar-SQUID imaging plate arrangement, (b) to verify the imaging principle, (c) measure the background rejection factor of the imaging plane, and (d) compare superconducting materials for the imaging plane. A phantom source field was measured at the sensors as a function of phantom distance from the sensor array to verify the imaging theory. Both the shape and absolute value of the measured and predicted curves agree very well indicating the system is behaving as a gradiometer in accordance with theory. The output from SQUIDs located behind the imaging surface that sense background fields can be used for software or analog background cancellation. Fields arising from sources close to the imaging plane were shielded form the background sensors by more than a factor of 1000. Measurement of the symmetry of sensor sensitivity to uniform fields exactly followed theoretical predictions.
Date: September 13, 1998
Creator: Kraus, R.R.; Flynn, E.R.; Espy, M.A.; Matlashov, A.; Overton, W.; Peters, M.V. et al.
Partner: UNT Libraries Government Documents Department

Optimization of Dedicated Scintimammography Procedure Using Detector Prototypes and Compressible Phantoms

Description: Results are presented on the optimization of the design and use of dedicated compact scintimammography gamma cameras. Prototype imagers with a field-of-view (FOV) of 5 cm x 5 cm, 10 cm x 10 cm and 15 cm x 20 cm were used in either a dual modality mode as an adjunct technique to digital x-ray mammography imagers or as stand-alone instruments such as dedicated breast SPECT and planar imagers. Experimental data was acquired to select the best imaging modality (SPECT or planar) to detect small lesions using Tc{sup 99m} radio-labeled pharmaceuticals. In addition, studies were preformed to optimize the imaging geometry. Results suggest that the preferred imaging geometry is planar imaging with two opposing detector heads while the breast is under compression, however further study of the dedicated breast SPECT is warranted.
Date: October 1, 2000
Creator: Majewski, S.; Kieper, D.; Curran, E.; Keppel, C.; Kross, B.; Palumbo, A. et al.
Partner: UNT Libraries Government Documents Department

Dual energy iodine contrast CT with monochromatic x-rays

Description: Computed tomography (CT) with monochromatic x-ray beams was used to image phantoms and a live rabbit using the preclinical Multiple Energy Computed Tomography (MECT) system at the National Synchrotron Light Source. MECT has a horizontal fan beam with a subject apparatus rotating about a vertical axis. Images were obtained at 43 keV for single-energy studies, and at energies immediately below and above the 33.17 keV iodine K-edge for dual-energy subtraction CT. Two CdWO{sub 4}-photodiode array detectors were used. The high-resolution detector (0.5 mm pitch, uncollimated) provided 14 line pair/cm in-plane spatial resolution, with lower image noise than conventional CT. Images with the low-resolution detector (1.844-mm pitch, collimated to 0.922 mm detector elements) had a sensitivity for iodine of {approx} 60 {micro}g/cc in 11-mm channels inside a 135 mm-diameter acrylic cylindrical phantom for a slice height of 2.5 mm and a surface does of {approx} 4 cGy. The image noise was {approx} 1 Hounsfield Unit (HU); it was {approx} 3 HU for the same phantom imaged with conventional CT at approximately the same dose, slice height, and spatial resolution ({approx} 7 lp/cm). These results show the potential advantage of MECT, despite present technical limitations.
Date: December 31, 1995
Creator: Dilmanian, F.A.; Wu, X.Y. & Kress, J.
Partner: UNT Libraries Government Documents Department

Air Kerma Calibration Factors and kch Values for PTW Soft X-ray, NACP and Roos Ionization Chambers at Very Low X-ray Energies (0.035 mm - 1.0 mm Al HVL)

Description: Several national and international protocols have been established for the dosimetry of x-ray beams used in radiotherapy. For the very low energy x-rays (0.035mm-1.0 mm Al HVL) only two codes are available: the UK IPEMB Code of Practice and the German standard, DIN 6809 Part 4. The measurement of very low energy x-ray beams is normally performed with parallel plate ionization chambers calibrated at a standards laboratory and characterized by an air kerma calibration factor N{sub k}. According to the IPEMB Code of Practice the absorbed dose in the user's beam should be determined by taking measurements with the parallel plate chamber positioned such that its entrance window is at the surface of a full-scatter water equivalent phantom. The absorbed dose to water can then be determined using an equation which includes a factor, k{sub ch}, which accounts for the change in response of the ionization chamber between the calibration in air and measurement at the surface of the phantom. N{sub k} and k{sub ch} values for the PTW soft X-ray, NACP and Roos ionization chambers are reported. It was found that k{sub ch} values varied from about 1.01 to 1.08 depending on the chamber, beam quality and phantom material. It is recommended that the IPEMB Code of Practice should be revised to incorporate these values.
Date: July 8, 1999
Creator: Ipe, Nisy E.
Partner: UNT Libraries Government Documents Department

Polarized Light Propagation in Biological Tissue and Tissue Phantoms

Description: Imaging through biologic tissue relies on the discrimination of weakly scattered from multiply scattered photons. The degree of polarization can be used as the discrimination criterion by which to reject multiply scattered photons. Polarized light propagation through biologic tissue is typically studied using tissue phantoms consisting of dilute aqueous suspensions of microsphere. We show that, although such phantoms are designed to match the macroscopic scattering properties of tissue (i.e.. the scattering coefficient, {mu}{sub 3}, and scattering anisotropy, g), they do not accurately represent biologic tissue for polarization-sensitive studies. In common tissue phantoms, such as dilute Intralipid and dilute 1-{micro}m-diameter polystyrene microsphere suspensions, we find that linearly polarized light is depolarized more quickly than circularly polarized light. In dense tissue, however, where scatterers are often located in close proximity to one another, circularly polarized light is depolarized similar to or more quickly than linearly polarized light. We also demonstrate that polarized light propagates differently in dilute versus densely packed microsphere suspensions, which may account for the differences seen between polarized light propagation in common dilute tissue phantoms versus dense biologic tissue.
Date: December 10, 1999
Creator: Sankaran, V.; Walsh, J.T. & Maitland, D.
Partner: UNT Libraries Government Documents Department

The development of early pediatric models and their application to radiation absorbed dose calculations

Description: This presentation will review and describe the development of pediatric phantoms for use in radiation dose calculations . The development of pediatric models for dose calculations essentially paralleled that of the adult. In fact, Snyder and Fisher at the Oak Ridge National Laboratory reported on a series of phantoms for such calculations in 1966 about two years before the first MIRD publication on the adult human phantom. These phantoms, for a newborn, one-, five-, ten-, and fifteen-year old, were derived from the adult phantom. The ``pediatric`` models were obtained through a series of transformations applied to the major dimensions of the adult, which were specified in a Cartesian coordinate system. These phantoms suffered from the fact that no real consideration was given to the influence of these mathematical transformations on the actual organ sizes in the other models nor to the relation of the resulting organ masses to those in humans of the particular age. Later, an extensive effort was invested in designing ``individual`` pediatric phantoms for each age based upon a careful review of the literature. Unfortunately, the phantoms had limited use and only a small number of calculations were made available to the user community. Examples of the phantoms, their typical dimensions, common weaknesses, etc. will be discussed.
Date: December 31, 1989
Creator: Poston, J. W.
Partner: UNT Libraries Government Documents Department

Monochromatic computed tomography of the human brain using synchrotron x rays: Technical feasibility

Description: A monochromatic computed tomography (CT) scanner is being developed at the X17 superconducting wiggler beamline at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, to image the human head and neck. The system configuration is one of a horizontal fan beam and an upright seated rotating subject. The purpose of the project are to demonstrate improvement in the image contrast and in the image quantitative accuracy that can be obtained in monochromatic CT and to apply the system to specific clinical research programs in neuroradiology. This paper describes the first phantom studies carried out with a prototype system, using the dual photon absorptiometry (DPA) method at energies of 20 and 39 Kev. The results show that improvements in image contrast and quantitative accuracy are possible with monochromatic DPA CT. Estimates of the clinical performance of the planned CT system are made on the basis of these initial results.
Date: December 31, 1991
Creator: Nachaliel, E.; Dilmanian, F. A.; Garrett, R. F.; Thomlinson, W. C.; Chapman, L. D.; Gmuer, N. F. et al.
Partner: UNT Libraries Government Documents Department

OSL Based Anthropomorphic Phantom and Real-Time Organ Dosimetry

Description: The overall objective of this project was the development of a dosimetry system that provides the direct measurement of organ does in real-time with a sensitivity that makes it an effective tool for applications in a wide variety of health physics applications. The system included the development of a real-time readout system for fiber optic coupled (FOC) dosimeters that is integrated with a state-of-art anthropomorphic phantom to provide instantaneous measures of organ doses throughout the phantom. The small size of the FOC detectors and optical fibers allow the sensitive volume of the detector to be located at organ centroids (or multiple locations distributed through the organ) within a tissue equivalent, anthropomorphic phantom without perturbing the tissue equivalent features of the phantom. The developed phantom/dosimetry system can be used in any environment where personnel may be exposed to gamma or x-ray radiations to provide the most accurate determinations of organ and effective doses possible to date.
Date: February 10, 2009
Creator: David E. Hintenlang, Ph.D
Partner: UNT Libraries Government Documents Department

Calibration of the Accuscan II IN Vivo System for High Energy Lung Counting

Description: This report describes the April 2011 calibration of the Accuscan II HpGe In Vivo system for high energy lung counting. The source used for the calibration was a NIST traceable lung set manufactured at the University of Cincinnati UCLL43AMEU & UCSL43AMEU containing Am-241 and Eu-152 with energies from 26 keV to 1408 keV. The lung set was used in conjunction with a Realistic Torso phantom. The phantom was placed on the RMC II counting table (with pins removed) between the v-ridges on the backwall of the Accuscan II counter. The top of the detector housing was positioned perpendicular to the junction of the phantom clavicle with the sternum. This position places the approximate center line of the detector housing with the center of the lungs. The energy and efficiency calibrations were performed using a Realistic Torso phantom (Appendix I) and the University of Cincinnati lung set. This report includes an overview introduction and records for the energy/FWHM and efficiency calibration including performance verification and validation counting. The Accuscan II system was successfully calibrated for high energy lung counting and verified in accordance with ANSI/HPS N13.30-1996 criteria.
Date: July 1, 2011
Creator: Perry, Ovard R. & Georgeson, David L.
Partner: UNT Libraries Government Documents Department

As-Built Modeling of Ojbects for Performance Assessment

Description: The goal of ''as-built'' computational modeling is to incorporate the most representative geometry and material information for an (fabricated or legacy) object into simulations. While most engineering finite element simulations are based on an object's idealized ''as-designed'' configuration with information obtained from technical drawings or computer-aided design models, ''as-built'' modeling uses nondestructive characterization and metrology techniques to provide the feature information. By incorporating more representative geometry and material features as initial conditions, the uncertainty in the simulation results can be reduced, providing a more realistic understanding of the event and object being modeled. In this paper, key steps and technology areas in the as-built modeling framework are: (1) inspection using non-destructive characterization (NDC) and metrology techniques; (2) data reduction (signal and image processing including artifact removal, data sensor fusion, and geometric feature extraction); and (3) engineering and physics analysis using finite element codes. We illustrate the process with a cylindrical phantom and include a discussion of the key concepts and areas that need improvement. Our results show that reasonable as-built initial conditions based on a volume overlap criteria can be achieved and that notable differences between simulations of the as-built and as-designed configurations can be observed for a given load case. Specifically, a volume averaged difference of accumulated plastic strain of 3% and local spatially varying differences up to 10%. The example presented provides motivation and justification to engineering teams for the additional effort required in the as-built modeling of high value parts. Further validation of the approach has been proposed as future work.
Date: September 12, 2005
Creator: Kokko, E J; Martz, H E; Chinn, D J; Childs, H R; Jackson, J A; Chambers, D H et al.
Partner: UNT Libraries Government Documents Department

Forward model for the superconducting imaging-surface meg system

Description: We have recently completed a novel whole-head MEG system based on the Superconducting Imaging-Surface (SIS) concept originally proposed by van Hulsteyn, et al.[l]. The SIS concept is generally described as a source near a superconducting surface. The source field induces Meissner currents in the superconductor equivalent to a source image 'behind' the surface. A sensor (SQUIDS in our system) placed on the source-side of the SIS will measure the superposed fields from the real and image sources. A second consequence of the Meissner effect is to shield the SQUIDS sensors near the SIS from external or background fields. The shape of the SIS used in our MEG system is a hemisphere with two cut-outs at the nominal ear-locations. A brim is added around the entire periphery with a smooth 0.5 cm radius transition between brim and hemisphere. Benefits of the SIS concept over existing systems include significantly enhanced signal-to-noise as a consequence of the SIS shielding and inherently generating pseudo-first order gradient fields at the sensors. One of the most significant challenges in realizing this system has been to accurately describe how the SIS system impacts the forward physics of any source model. Two approaches have been examined. The first is a hybrid analytical and empirical model using the analytic formalism to describe the hemisphere [1] and a correction matrix derived from empirical measurements to correct for edge effects. This approach proved overly complex and difficult in practice to obtain sufficient empirical data to derive a well-conditioned correction matrix. The second approach, reported here, was to develop a boundary element model (BEM) description of the SIS using the exact as-built geometry. Each element is described by a uniform magnetization arising from a distribution of Meissner currents in the superconductor such that B{perpendicular} = 0 at the surface. B{sub i} at ...
Date: January 1, 2001
Creator: Kraus, Robert H., Jr.; Matlachov, A. N. (Andrei N.); Espy, M. A. (Michelle A.); Maharajh, K. (Keeran) & Volegov, P. (Petr)
Partner: UNT Libraries Government Documents Department

Performance of a novel squid-based superconducting imaging-surface magnetoencephalography system

Description: Performance for a recently completed whole-head magnetoencephalography system using a superconducting imaging-surface (SIS) surrounding an array of 150 SQUID magnetometers is reported. The helmetlike SIS is hemispherical in shape with a brim. Conceptually, the SIS images nearby sources onto the SQUIDs while shielding sensors from distant 'noise' sources. A finite element method (FEM) description using the as-built geometry was developed to describe the SIS effect on source fields by imposing B(surface)=0. Sensors consist of 8mm x 8mm SQUID magnetometers with 0.84nT/F sensitivity and <3fT/vHz noise. A series of phantom experiments to verify system efficacy have been completed. Simple dry-wire phantoms were used to eliminate model dependence from our results. Phantom coils were distributed throughout the volume encompassed by the array with a variety of orientations. Each phantom coil was precisely machined and located to better than 25{micro}m and 10mRad accuracy. Excellent agreement between model-calculated and measured magnetic field distributions of all phantom coil positions and orientations was found. Good agreement was found between modeled and measured shielding of the SQUIDs from sources external to the array showing significant frequency-independent shielding. Phantom localization precision was better than 0.5mm at all locations with a mean of better than 0.3mm.
Date: January 1, 2001
Creator: Matlochov, A. (Andrei); Espy, M. A. (Michelle A.); Volegov, P. (Petr); Maharajh, K. (Keeran); Flynn, E. R. (Edward. R.) & Kraus, Robert H., Jr.
Partner: UNT Libraries Government Documents Department