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2D spatial gain profiles in multiple-pulse driven Ne-like Ge lasers

Description: In this paper, we present the direct spatial measurement of the two-dimensional gain profiles for the Ne-like Ge 196 Å laser line using a slab target illuminated by the multiple pulse technique. To understand the spatial dependence for Ge plasmas driven by a series of 100 ps pulses 400 ps apart we did a series of Nova experiments backlighting short Ge amplifiers. Two-dimensional, high-resolution, spatial images of the 196 Å laser emission from the output aperture of the amplifiers were measured to determine the spatial position of the gain. The amplifier lengths were chosen to be short enough to avoid the significant refraction effects which have dominated the analysis of previous near field imaging experiments. To assure good temporal overlap, the traveling wave geometry was used to illuminate both the amplifier and backlighter. The amplifier design included a wire fiducial that provided an absolute spatial reference and avoided the usual difficulty of determining the location of the target surface. We compare the measured spatial gain profiles with simulations done using LASNEX, which calculates the hydrodynamic evolution of the plasma, and XRASER, which uses the temperatures and densities from LASNEX to do the gain and kinetics calculations.
Date: September 21, 1998
Creator: Dunn, J; Li, Y; Nilsen, J & Osterheld, A L
Partner: UNT Libraries Government Documents Department

Draft photosensor characterization report

Description: The report presents the results of laboratory measurements performed on The Watt Stopper's LS-201 photosensor at the Lawrence Berkeley National Laboratory in January 2003. The purpose of these measurements was to characterize the spatial and spectral response function of the LS-201 photosensor. Sample results of the spectral response and spatial response are shown.
Date: February 23, 2003
Creator: Rubinstein, Francis M.; Yazdanian, Mehry & Galvin, James
Partner: UNT Libraries Government Documents Department

Systematic Neighborhood Observations at High Spatial Resolution: Methodology and Assessment of Potential Benefits

Description: This article describes a systematic neighborhood observation instrument for collecting data at very high spatial resolution to collect data in a low-income minority neighborhood in Dallas, TX.
Date: January 20, 2011
Creator: Leonard, Tammy; O'Brien Caughy, Margaret; Mays, Judith K. & Murdoch, James
Partner: UNT College of Arts and Sciences


Description: In this investigation, a simple experimental technique, dot-matrix deposition and mapping, was developed to study the full-field deformation in a polymeric foam specimen. One of the advantages of using this technique is that it can be easily applied to situations where large deformations are involved. The spatial resolution of the current technique is not as high as the digital image correlation method and some other optical techniques. Nevertheless, because the largest cell diameter of the polyurethane foam studied in this investigation is about 1 mm, the smallest length scale over which the polymeric foam material can be treated as a homogeneous solid would be at least several millimeters. For the element size used in the present study in the range of 2.5 x 2.5 mm, the dot-matrix deposition and mapping technique would provide enough detail about the behavior of polymeric foam materials under complicated deformation states and under complicated loading conditions. It will also provide useful information to compare with numerical simulations so that the constitutive models can be validated.
Date: March 1, 2001
Creator: LIU, C. & AL, ET
Partner: UNT Libraries Government Documents Department

Towards sub-10 nm resolution zone plates using the overlaynanofabrication processes

Description: Soft x-ray zone plate microscopy has proven to be a valuable imaging technique for nanoscale studies. It complements nano-analytic techniques such as electron and scanning probe microscopies. One of its key features is high spatial resolution. We developed an overlay nanofabrication process which allows zone plates of sub-20 nm zone widths to be fabricated. Zone plates of 15 nm outer zones were successfully realized using this process, and sub-15 nm resolution was achieved with these zone plates. We extend the overlay process to fabricating zone plates of 12 nm outer zones, which is expected to achieve 10 nm resolution. In addition, we have identified a pathway to realizing sub-10 nm resolution, high efficiency zone plates with tilted zones using the overlay process.
Date: January 23, 2008
Creator: Chao, Weilun; Anderson, Erik H.; Fischer, Peter & Kim, Dong-Hyun
Partner: UNT Libraries Government Documents Department

Near field imaging of a saturated table top x-ray laser

Description: High resolution 2D imaging experiment on the saturated 18.9 nm Ni-like soft X-ray laser is presented. The imaging experiment allows measurement of the absolute output energy and intensity of the X-ray laser, while it gives detailed information on the spatial characteristics of the X-ray laser for understanding the physics and further improving the performance of the X-ray laser.
Date: June 25, 1999
Creator: Dunn, J; Li, Y; Nilsen, J; Osterheld, A & Shlyaptsev, V N
Partner: UNT Libraries Government Documents Department

Superresolution and Synthetic Aperture Radar

Description: Superresolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realized. In this study we investigate the potential application of superresolution concepts to synthetic aperture radar. The analytical basis for superresolution theory is discussed. The application of the concept to synthetic aperture radar is investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. A criterion for judging superresolution processing of an image is presented.
Date: May 1, 2001
Partner: UNT Libraries Government Documents Department

Regularization Analysis of SAR Superresolution

Description: Superresolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realized. In this study we investigate the potential application of superresolution concepts to synthetic aperture radar. The analytical basis for superresolution theory is discussed. In a previous report the application of the concept to synthetic aperture radar was investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. This work treats the problem from the standpoint of regularization. Both the operator inversion approach and the regularization approach show that the ability to superresolve SAR imagery is severely limited by system noise.
Date: April 1, 2002
Partner: UNT Libraries Government Documents Department

Characterization of Coupled Hydrologic Biogeochemical Processes Using Geophysical Data

Description: Biogeochemical and hydrological processes are naturally coupled and variable over a wide range of spatial and temporal scales. Additionally, many remediation approaches also induce dynamic transformations in the system. It is widely accepted that effective remediation requires a better understanding of coupled processes than is currently available. Further complicating the problem is the inability to collect the necessary measurements at a high enough spatial resolution yet over a large enough volume for understanding field-scale transformations. Our research includes two key objectives: (1) Improving the understanding of certain coupled processes, and (2) Investigating the capability to characterize and monitor coupled processes at appropriate resolutions and spatial scales using geophysical data.
Date: June 1, 2003
Creator: Hubbard, Susan
Partner: UNT Libraries Government Documents Department

2003 Laser Diagnostic in Combustion Conference

Description: The GRC Laser Diagnostics in Combustion aims at bringing together scientists and engineers working in the front edge of research and development to discuss and find new ways to solve problems connected to combustion diagnostics. Laser-based techniques have proven to be very efficient tools for studying combustion processes thanks to features as non-intrusiveness in combination with high spatial and temporal resolution. Major tasks for the community are to develop and apply techniques for quantitative measurements with high precision e.g of species concentrations, temperatures, velocities and particles characteristics (size and concentration). These issues are of global interest, considering that the major part of the World's energy conversion comes from combustion sources and the influence combustion processes have on the environment and society.
Date: September 10, 2004
Creator: Allen, Mark G.
Partner: UNT Libraries Government Documents Department

Scaling Behavior of Barkhausen Avalanches along the Hysteresis loop in Nucleation-Mediated Magnetization Reversal Process

Description: We report the scaling behavior of Barkhausen avalanches for every small field step along the hysteresis loop in CoCrPt alloy film having perpendicular magnetic anisotropy. Individual Barkhausen avalanche is directly observed utilizing a high-resolution soft X-ray microscopy that provides real space images with a spatial resolution of 15 nm. Barkhausen avalanches are found to exhibit power-law scaling behavior at all field steps along the hysteresis loop, despite their different patterns for each field step. Surprisingly, the scaling exponent of the power-law distribution of Barkhausen avalanches is abruptly altered from 1 {+-} 0.04 to 1.47 {+-} 0.03 as the field step is close to the coercive field. The contribution of coupling among adjacent domains to Barkhausen avalanche process affects the sudden change of the scaling behavior observed at the coercivity-field region on the hysteresis loop of CoCrPt alloy film.
Date: October 14, 2008
Creator: Im, Mi-Young; Fischer, Peter; Kim, D.-H. & Shin, S.-C.
Partner: UNT Libraries Government Documents Department

Probing the spin polarization of current by soft x-ray imaging of current-induced magnetic vortex dynamics

Description: Time-resolved soft X-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micron-sized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67 {+-} 0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.
Date: December 9, 2008
Creator: Kasai, Shinya; Fischer, Peter; Im, Mi-Young; Yamada, Keisuke; Nakatani, Yoshinobu; Kobayashi, Kensuke et al.
Partner: UNT Libraries Government Documents Department

Inspection 13.2 nm table-top full-field microscope

Description: We present results on a table-top microscope that uses an EUV stepper geometry to capture full-field images with a halfpitch spatial resolution of 55 nm. This microscope uses a 13.2 nm wavelength table-top laser for illumination and acquires images of reflective masks with exposures of 20 seconds. These experiments open the path to the realization of high resolution table-top imaging systems for actinic defect characterization.
Date: February 23, 2009
Creator: Brizuela, F.; Wang, Y.; Brewer, C. A.; Pedaci, F.; Chao, W.; Anderson, E. H. et al.
Partner: UNT Libraries Government Documents Department

Ground surface temperature reconstructions: Using in situ estimates for thermal conductivity acquired with a fiber-optic distributed thermal perturbation sensor

Description: We have developed a borehole methodology to estimate formation thermal conductivity in situ with a spatial resolution of one meter. In parallel with a fiber-optic distributed temperature sensor (DTS), a resistance heater is deployed to create a controlled thermal perturbation. The transient thermal data is inverted to estimate the formation's thermal conductivity. We refer to this instrumentation as a Distributed Thermal Perturbation Sensor (DTPS), given the distributed nature of the DTS measurement technology. The DTPS was deployed in permafrost at the High Lake Project Site (67 degrees 22 minutes N, 110 degrees 50 minutes W), Nunavut, Canada. Based on DTPS data, a thermal conductivity profile was estimated along the length of a wellbore. Using the thermal conductivity profile, the baseline geothermal profile was then inverted to estimate a ground surface temperature history (GSTH) for the High Lake region. The GSTH exhibits a 100-year long warming trend, with a present-day ground surface temperature increase of 3.0 {+-} 0.8 C over the long-term average.
Date: October 10, 2008
Creator: Freifeld, B. M.; Finsterle, S.; Onstott, T. C.; Toole, P. & Pratt, L. M.
Partner: UNT Libraries Government Documents Department

Extracellular matrix control of mammary gland morphogenesis and tumorigenesis: insights from imaging

Description: The extracellular matrix (ECM), once thought to solely provide physical support to a tissue, is a key component of a cell's microenvironment responsible for directing cell fate and maintaining tissue specificity. It stands to reason, then, that changes in the ECM itself or in how signals from the ECM are presented to or interpreted by cells can disrupt tissue organization; the latter is a necessary step for malignant progression. In this review, we elaborate on this concept using the mammary gland as an example. We describe how the ECM directs mammary gland formation and function, and discuss how a cell's inability to interpret these signals - whether as a result of genetic insults or physicochemical alterations in the ECM - disorganizes the gland and promotes malignancy. By restoring context and forcing cells to properly interpret these native signals, aberrant behavior can be quelled and organization re-established. Traditional imaging approaches have been a key complement to the standard biochemical, molecular, and cell biology approaches used in these studies. Utilizing imaging modalities with enhanced spatial resolution in live tissues may uncover additional means by which the ECM regulates tissue structure, on different length scales, through its pericellular organization (short-scale) and by biasing morphogenic and morphostatic gradients (long-scale).
Date: October 23, 2008
Creator: Ghajar, Cyrus M & Bissell, Mina J
Partner: UNT Libraries Government Documents Department

Tagged Neutron Source for API Inspection Systems with Greatly Enhanced Spatial Resolution

Description: We recently developed induced fission and transmission imaging methods with time- and directionally-tagged neutrons offer new capabilities for characterization of fissile material configurations and enhanced detection of special nuclear materials (SNM). An Advanced Associated Particle Imaging (API) generator with higher angular resolution and neutron yield than existing systems is needed to fully exploit these methods.
Date: June 4, 2012
Partner: UNT Libraries Government Documents Department

Ultra high resolution soft x-ray tomography

Description: Ultra high resolution three dimensional images of a microscopic test object were made with soft x-rays using a scanning transmission x-ray microscope. The test object consisted of two different patterns of gold bars on silicon nitride windows that were separated by {approximately}5{mu}m. A series of nine 2-D images of the object were recorded at angles between {minus}50 to +55 degrees with respect to the beam axis. The projections were then combined tomographically to form a 3-D image by means of an algebraic reconstruction technique (ART) algorithm. A transverse resolution of {approximately}1000 {Angstrom} was observed. Artifacts in the reconstruction limited the overall depth resolution to {approximately}6000 {Angstrom}, however some features were clearly reconstructed with a depth resolution of {approximately}1000 {Angstrom}. A specially modified ART algorithm and a constrained conjugate gradient (CCG) code were also developed as improvements over the standard ART algorithm. Both of these methods made significant improvements in the overall depth resolution bringing it down to {approximately}1200 {Angstrom} overall. Preliminary projection data sets were also recorded with both dry and re-hydrated human sperm cells over a similar angular range.
Date: July 19, 1995
Creator: Haddad, W.S.; Trebes, J.E. & Goodman, D.M.
Partner: UNT Libraries Government Documents Department

Conceptual design for a user-friendly adaptive optics system at Lick Observatory

Description: In this paper, we present a conceptual design for a general-purpose adaptive optics system, usable with all Cassegrain facility instruments on the 3 meter Shane telescope at the University of California`s Lick Observatory located on Mt. Hamilton near San Jose, California. The overall design goal for this system is to take the sodium-layer laser guide star adaptive optics technology out of the demonstration stage and to build a user-friendly astronomical tool. The emphasis will be on ease of calibration, improved stability and operational simplicity in order to allow the system to be run routinely by observatory staff. A prototype adaptive optics system and a 20 watt sodium-layer laser guide star system have already been built at Lawrence Livermore National Laboratory for use at Lick Observatory. The design presented in this paper is for a next- generation adaptive optics system that extends the capabilities of the prototype system into the visible with more degrees of freedom. When coupled with a laser guide star system that is upgraded to a power matching the new adaptive optics system, the combined system will produce diffraction-limited images for near-IR cameras. Atmospheric correction at wavelengths of 0.6-1 mm will significantly increase the throughput of the most heavily used facility instrument at Lick, the Kast Spectrograph, and will allow it to operate with smaller slit widths and deeper limiting magnitudes. 8 refs., 2 figs.
Date: March 8, 1996
Creator: Bissinger, H.D.; Olivier, S. & Max, C.
Partner: UNT Libraries Government Documents Department

Nanometer resolution BPM using damped slot resonator

Description: A new type of high resolution beam position monitor called the damped slot resonator rf BPM has been installed at the focal point of the FFTB. It is comprised of a cylindrical resonant cavity with a tuned choke joint at the TM{sub 110} resonances. The BPM has a large dynamic range from the nm to mm range with a minimum resolution of 1 nm. We report on the rf cavity cold tests performance, processing electronics design, and some experimental results obtained in obtained in the high energy electron beam line.
Date: May 1, 1995
Creator: Hartman, S.C.; Shintake, T. & Akasaka, N.
Partner: UNT Libraries Government Documents Department

Towards sub-{Angstrom} resolution through incoherent imaging

Description: As first pointed out by Lord Rayleigh a century ago, incoherent imaging offers a substantial resolution enhancement compared to coherent imaging, together with freedom from phase contrast interference effects and contrast oscillations. In the STEM configuration, with a high angle annular detector to provide the transverse incoherence, the image also shows strong Z-contrast, sufficient in the case of a 300 kV STEM to image single Pt and Rh atoms on a {gamma}-alumina support. The annular detector provides complementarity to a bright field detector of the same size. For weakly scattering specimens, it shows greater contrast than the incoherent bright field image, and also facilitates EELS analysis at atomic resolution, using the Z-contrast image to locate the probe with sub-{angstrom} precision. The inner radius of the annular detector can be chosen to reduce the transverse coherence length to well below the spacings needed to resolve the object, a significant advantage compared to light microscopy.
Date: April 1, 1997
Creator: Pennycook, S.J.; Chisholm, M.F. & Nellist, P.D.
Partner: UNT Libraries Government Documents Department