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A 10-Hz Terawatt Class Ti:Sapphire Laser System: Development and Applications (open access)

A 10-Hz Terawatt Class Ti:Sapphire Laser System: Development and Applications

We developed a two stage Ti:Sapphire laser system to generate 16 mJ/80fs laser pulses at the pulse repetition rate of 10 Hz. The key deriver for the present design is implementing a highly efficient symmetric confocal pre-amplifier and employing a simple, inexpensive synchronization scheme relying only on a commercial digital delay-generator. We characterized the amplified pulses in spatial-, spectral-, and temporal-domains. The laser system was used to investigate various nonlinear optical processes, and to modify the optical properties of metal- and semiconductor-surfaces. We are currently building a third amplifier to boost the laser power to the multi-terawatt range.
Date: January 12, 2010
Creator: Sharma, A. K.; Smedley, J.; Tsang, T. & Rao, T.
System: The UNT Digital Library
500 MW X-BAND RF SYSTEM OF A 0.25 GEV ELECTRON LINAC FOR ADVANCED COMPTON SCATTERING SOURCE APPLICATION (open access)

500 MW X-BAND RF SYSTEM OF A 0.25 GEV ELECTRON LINAC FOR ADVANCED COMPTON SCATTERING SOURCE APPLICATION

A Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering light source is being developed at LLNL in collaboration with SLAC National Accelerator Laboratory. The electron beam for the Compton scattering interaction will be generated by a X-band RF gun and a X-band LINAC at the frequency of 11.424 GHz. High power RF in excess of 500 MW is needed to accelerate the electrons to energy of 250 MeV or greater for the interaction. Two high power klystron amplifiers, each capable of generating 50 MW, 1.5 msec pulses, will be the main high power RF sources for the system. These klystrons will be powered by state of the art solid-state high voltage modulators. A RF pulse compressor, similar to the SLED II pulse compressor, will compress the klystron output pulse with a power gain factor of five. For compactness consideration, we are looking at a folded waveguide setup. This will give us 500 MW at output of the compressor. The compressed pulse will then be distributed to the RF gun and to six traveling wave accelerator sections. Phase and amplitude control are located at the RF gun input and additional control points along the LINAC to allow for parameter control during operation. This high …
Date: May 12, 2010
Creator: Chu, T S; Anderson, S G; Gibson, D J; Hartemann, F V; Marsh, R A; Siders, C et al.
System: The UNT Digital Library
Actinic imaging of native and programmed defects on a full-field mask (open access)

Actinic imaging of native and programmed defects on a full-field mask

We describe the imaging and characterization of native defects on a full field extreme ultraviolet (EUV) mask, using several reticle and wafer inspection modes. Mask defect images recorded with the SEMA TECH Berkeley Actinic Inspection Tool (AIT), an EUV-wavelength (13.4 nm) actinic microscope, are compared with mask and printed-wafer images collected with scanning electron microscopy (SEM) and deep ultraviolet (DUV) inspection tools. We observed that defects that appear to be opaque in the SEM can be highly transparent to EUV light, and inversely, defects that are mostly transparent to the SEM can be highly opaque to EUV. The nature and composition of these defects, whether they appear on the top surface, within the multilayer coating, or on the substrate as buried bumps or pits, influences both their significance when printed, and their detectability with the available techniques. Actinic inspection quantitatively predicts the characteristics of printed defect images in ways that may not be possible with non-EUV techniques. As a quantitative example, we investigate the main structural characteristics of a buried pit defect based on EUV through-focus imaging.
Date: March 12, 2010
Creator: Mochi, I.; Goldberg, K. A.; Fontaine, B. La; Tchikoulaeva, A. & Holfeld, C.
System: The UNT Digital Library
ADVANCED X-BAND TEST ACCELERATOR FOR HIGH BRIGHTNESS ELECTRON AND GAMMA RAY BEAMS (open access)

ADVANCED X-BAND TEST ACCELERATOR FOR HIGH BRIGHTNESS ELECTRON AND GAMMA RAY BEAMS

In support of Compton scattering gamma-ray source efforts at LLNL, a multi-bunch test stand is being developed to investigate accelerator optimization for future upgrades. This test stand will enable work to explore the science and technology paths required to boost the current 10 Hz monoenergetic gamma-ray (MEGa-Ray) technology to an effective repetition rate exceeding 1 kHz, potentially increasing the average gamma-ray brightness by two orders of magnitude. Multiple bunches must be of exceedingly high quality to produce narrow-bandwidth gamma-rays. Modeling efforts will be presented, along with plans for a multi-bunch test stand at LLNL. The test stand will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. The photoinjector will be a high gradient standing wave structure, featuring a dual feed racetrack coupler. The accelerator will increase the electron energy so that the emittance can be measured using quadrupole scanning techniques. Multi-bunch diagnostics will be developed so that the beam quality can be measured and compared with theory. Design will be presented with modeling simulations, and layout plans.
Date: May 12, 2010
Creator: Marsh, R A; Anderson, S G; Barty, C P; Chu, T S; Ebbers, C A; Gibson, D J et al.
System: The UNT Digital Library
Aerosol indirect effects ? general circulation model intercomparison and evaluation with satellite data (open access)

Aerosol indirect effects ? general circulation model intercomparison and evaluation with satellite data

Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth ({tau}{sub a}) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (N{sub d}) compares relatively well to the satellite data at least over the ocean. The relationship between {tau}{sub a} and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (f{sub cld}) and {tau}{sub a} as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the …
Date: March 12, 2010
Creator: Quaas, Johannes; Ming, Yi; Menon, Surabi; Takemura, Toshihiko; Wang, Minghuai; Penner, Joyce E. et al.
System: The UNT Digital Library
ALLOYING-DRIVEN PHASE STABILITY IN GROUP VB TRANSITION METALS UNDER COMPRESSION (open access)

ALLOYING-DRIVEN PHASE STABILITY IN GROUP VB TRANSITION METALS UNDER COMPRESSION

None
Date: July 12, 2010
Creator: Landa, A.; Soderlind, P.; Velikokhatnyi, O. I.; Naumov, I. I.; Ruban, A. V.; Peil, O. E. et al.
System: The UNT Digital Library
Alphabet Soup - An Overview of Diagnostic Techniques (open access)

Alphabet Soup - An Overview of Diagnostic Techniques

This report gives an overview of diagnostic techniques of "Alphabet Soup".
Date: October 12, 2010
Creator: Smedley, J.
System: The UNT Digital Library
Applications of Laser and Synchrotron Based ARPES to Photocathode Research (open access)

Applications of Laser and Synchrotron Based ARPES to Photocathode Research

Laser angle resolved photoelectron spectroscopy (ARPES) provides unique information about angle and energy distribution of photoelectrons. Laser ARPES gives unique insight into how NEA materials work. ARPES combined with some ancillary measurements gives a very complete picture of system electronic physics. For H:C[100] there is now a clear program for engineering as well as development analogous systems. ARPES well suited for identifying 'ideal' photocathodes with intrinsically low emittance and high QE.
Date: October 12, 2010
Creator: Rameau, J.; Smedley. J.; Muller, E.; Kidd, T.; Johnson, P.; Allen, P. et al.
System: The UNT Digital Library
Atmospheric Effects on the Performance of Cdznte Single Crystal Detectors (open access)

Atmospheric Effects on the Performance of Cdznte Single Crystal Detectors

The production of high-quality ternary single-crystal materials for radiation detectors has progressed over the past 15 years. One of the more common materials being studied is CdZnTe (CZT), which can be grown using several methods to produce detector-grade materials. The work presented herein examines the effects of environmental conditions including temperature and humidity on detector performance [full-width at half-maximum (FWHM)] using the single pixel with guard detector configuration. The effects of electrical probe placement, reproducibility, and aging are also presented.
Date: May 12, 2010
Creator: Washington, A.; Duff, M. & Teague, L.
System: The UNT Digital Library
Beam commissioning results for the RFQ and MEBT of the EBIS based preinjector for RHIC (open access)

Beam commissioning results for the RFQ and MEBT of the EBIS based preinjector for RHIC

The EBIS based preinjector for both the Relativistic Heavy Ion Collider (RHIC) and NASA Space Radiation Laboratory (NSRL) is now being commissioned at Brookhaven National Laboratory (BNL). In 2008, the RFQ for the project was delivered and commissioned using Test EBIS, which was built to demonstrate the high current EBIS's performance. A dedicated beamline after the RFQ was assembled to confirm the RFQ's performance, and the beam energy was measured by a bending dipole magnet. In November 2009, the RFQ was moved to the final location and the vanes were realigned. The beam commissioning with the RHIC-EBIS was started again during March 2010. The RFQ accelerates ions from 17 keV/u to 300 keV/u and operates at 100.625 MHz. It is followed by a short Medium Energy Beam Transport (MEBT), which consists of four quadrupoles and one buncher cavity. Some temporary diagnostics for this commissioning include an emittance probe, TOF system, fast Faraday cup, and beam current measurement units. As of September 2010, the RFQ and the MEBT show expected performance with He{sup +}, Au{sup 32+} and Fe{sup 20+} beams. Further commissioning for higher intensity beams is in progress.
Date: September 12, 2010
Creator: Okamura, M.; Alessi, J.; Beebe, E.; Kondo, K.; Lambiase, R.; Lockey, R. et al.
System: The UNT Digital Library
Calibration of a Flat Field Soft X-ray Grating Spectrometer for Laser Produced Plasmas (open access)

Calibration of a Flat Field Soft X-ray Grating Spectrometer for Laser Produced Plasmas

We have calibrated the x ray response of a variable line spaced grating spectrometer, known as the VSG, at the Fusion and Astrophysics Data and Diagnostic Calibration Facility at the Lawrence Livermore National Laboratory (LLNL). The VSG has been developed to diagnose laser produced plasmas, such as those created at the Jupiter Laser Facility and the National Ignition Facility at LLNL, and at both the Omega and Omega EP lasers at University of Rochester's Laboratory for Laser Energetics. The bandwidth of the VSG spans the range from {approx} 6 to 60 {angstrom}. The calibration results present here include the VSG's dispersion and quantum efficiency. The dispersion is determined by measuring the x rays emitted from hydrogen-like and helium-like ions of carbon, nitrogen, oxygen, neon, and aluminum. The quantum efficiency is calibrated to an accuracy of 30% or better by normalizing the x ray intensities recorded by the VSG to those simultaneously recorded by an x ray microcalorimeter spectrometer.
Date: May 12, 2010
Creator: Park, J.; Brown, G. V.; Schneider, M. B.; Baldis, H. A.; Beiersdorfer, P.; Cone, K. V. et al.
System: The UNT Digital Library
Carbon contamination topography analysis of EUV masks (open access)

Carbon contamination topography analysis of EUV masks

The impact of carbon contamination on extreme ultraviolet (EUV) masks is significant due to throughput loss and potential effects on imaging performance. Current carbon contamination research primarily focuses on the lifetime of the multilayer surfaces, determined by reflectivity loss and reduced throughput in EUV exposure tools. However, contamination on patterned EUV masks can cause additional effects on absorbing features and the printed images, as well as impacting the efficiency of cleaning process. In this work, several different techniques were used to determine possible contamination topography. Lithographic simulations were also performed and the results compared with the experimental data.
Date: March 12, 2010
Creator: Fan, Y.-J.; Yankulin, L.; Thomas, P.; Mbanaso, C.; Antohe, A.; Garg, R. et al.
System: The UNT Digital Library
Challenges of Algebraic Multigrid across Multicore Architectures (open access)

Challenges of Algebraic Multigrid across Multicore Architectures

Algebraic multigrid (AMG) is a popular solver for large-scale scientific computing and an essential component of many simulation codes. AMG has shown to be extremely efficient on distributed-memory architectures. However, when executed on modern multicore architectures, we face new challenges that can significantly deteriorate AMG's performance. We examine its performance and scalability on three disparate multicore architectures: a cluster with four AMD Opteron Quad-core processors per node (Hera), a Cray XT5 with two AMD Opteron Hex-core processors per node (Jaguar), and an IBM BlueGene/P system with a single Quad-core processor (Intrepid). We discuss our experiences on these platforms and present results using both an MPI-only and a hybrid MPI/OpenMP model. We also discuss a set of techniques that helped to overcome the associated problems, including thread and process pinning and correct memory associations.
Date: April 12, 2010
Creator: Baker, A H; Gamblin, T; Schulz, M & Yang, U M
System: The UNT Digital Library
Commissioning of the EBIS-based heavy ion preinjector at Brookhaven (open access)

Commissioning of the EBIS-based heavy ion preinjector at Brookhaven

The status is presented of the commissioning of a new heavy ion preinjector at Brookhaven National Laboratory. This preinjector uses an Electron Beam Ion Source (EBIS), and an RFQ and IH Linac, both operating at 100.625 MHz, to produce 2 MeV/u ions of any species for use, after further acceleration, at the Relativistic Heavy Ion Collider (RHIC) and the NASA Space Radiation Laboratory (NSRL). Among the increased capabilities provided by this preinjector are the ability to produce ions of any species, and the ability to switch between multiple species in 1 second, to simultaneously meet the needs of both science programs. For initial setup, helium beam from EBIS was injected and circulated in the Booster synchrotron. Following this, accelerated Au{sup 32+} and Fe{sup 20+} beams were transported to the Booster injection point, fulfilling DOE requirements for project completion.
Date: September 12, 2010
Creator: Alessi, J.; Beebe, E.; Binello, S.; Hoff, L.; Kondo, K.; Lambiase, R. et al.
System: The UNT Digital Library
A Comprehensive Analysis of Uncertainties Affecting the Stellar Mass-Halo Mass Relation for 0<z<4 (open access)

A Comprehensive Analysis of Uncertainties Affecting the Stellar Mass-Halo Mass Relation for 0<z<4

We conduct a comprehensive analysis of the relationship between central galaxies and their host dark matter halos, as characterized by the stellar mass - halo mass (SM-HM) relation, with rigorous consideration of uncertainties. Our analysis focuses on results from the abundance matching technique, which assumes that every dark matter halo or subhalo above a specific mass threshold hosts one galaxy. We provide a robust estimate of the SM-HM relation for 0 &lt; z &lt; 1 and discuss the quantitative effects of uncertainties in observed galaxy stellar mass functions (GSMFs) (including stellar mass estimates and counting uncertainties), halo mass functions (including cosmology and uncertainties from substructure), and the abundance matching technique used to link galaxies to halos (including scatter in this connection). Our analysis results in a robust estimate of the SM-HM relation and its evolution from z=0 to z=4. The shape and evolution are well constrained for z &lt; 1. The largest uncertainties at these redshifts are due to stellar mass estimates (0.25 dex uncertainty in normalization); however, failure to account for scatter in stellar masses at fixed halo mass can lead to errors of similar magnitude in the SM-HM relation for central galaxies in massive halos. We also investigate …
Date: May 12, 2010
Creator: Behroozi, Peter S.; Conroy, Charlie & Wechsler, Risa H.
System: The UNT Digital Library
Compressible gas flow through micro-capillary fill-tubes on NIF targets- modeling and experiments (open access)

Compressible gas flow through micro-capillary fill-tubes on NIF targets- modeling and experiments

None
Date: February 12, 2010
Creator: Bhandarkar, S D; Parham, T G & Fair, J E
System: The UNT Digital Library
Cyclooctatetraenes Tetrakis-Annelated with α-Dithio- or α-Diselenocarbonyl Groups: Diradicals Predicted To Have Ground States with 10 π Electrons in the Eight-Membered Ring and Two-Center, Three-Electron, σ Bonds between Two Pairs of Chalcogen Atoms (open access)

Cyclooctatetraenes Tetrakis-Annelated with α-Dithio- or α-Diselenocarbonyl Groups: Diradicals Predicted To Have Ground States with 10 π Electrons in the Eight-Membered Ring and Two-Center, Three-Electron, σ Bonds between Two Pairs of Chalcogen Atoms

Article on cyclooctatetraenes tetrakis-annelated with α-dithio- or α-diselenocarbonyl groups.
Date: February 12, 2010
Creator: Zhou, Xin; Hrovat, David A. & Borden, Weston T.
System: The UNT Digital Library
Development of a Time-resolved Soft X-ray Spectrometer for Laser Produced Plasma Experiments (open access)

Development of a Time-resolved Soft X-ray Spectrometer for Laser Produced Plasma Experiments

A 2400 line/mm variable spaced grating spectrometer (VSG) has been used to measure soft x-ray emission (8-22 {angstrom}) from laser-produced plasma experiments at Lawrence Livermore National Laboratory's Compact Multipulse Terrawatt (COMET) Laser Facility. The spectrometer was coupled to a Kentech x-ray streak camera to study the temporal evolution of soft x-rays emitted from the back of mylar and copper foils irradiated at 10{sup 15} W/cm{sup 2}. The instrument demonstrated a resolving power of {approx} 120 at 19 {angstrom} with a time resolution of 31 ps. The time-resolved copper emission spectrum was consistent with a photodiode monitoring the laser temporal pulse shape and indicated that the soft x-ray emission follows the laser heating of the target. The time and spectral resolution of this diagnostic make it useful for studies of high temperature plasmas.
Date: May 12, 2010
Creator: Cone, K. V.; Dunn, J.; Schneider, M. B.; Baldis, H. A.; Brown, G. V.; Emig, J. et al.
System: The UNT Digital Library
Development of stripper options for FRIB (open access)

Development of stripper options for FRIB

The US Department of Energy Facility for Rare Isotope Beams (FRIB) at Michigan State University includes a heavy ion superconducting linac capable of accelerating all ions up to uranium with energies higher than 200 MeV/u and beam power up to 400 kW. To achieve these goals with present ion source performance it is necessary to accelerate simultaneously two charge states of uranium from the ion source in the first section of the linac. At an energy of approximately 16.5 MeV/u it is planned to strip the uranium beam to reduce the voltage needed in the rest of the linac to achieve the final energy. Up to five different charge states are planned to be accelerated simultaneously after the stripper. The design of the stripper is a challenging problem due to the high power deposited (approximately 0.7 kW) in the stripper media by the beam in a small spot. To assure success of the project we have established a research and development program that includes several options: carbon or diamond foils, liquid lithium films, gas strippers and plasma strippers. We present in this paper the status of the different options.
Date: September 12, 2010
Creator: Marti, F.; Hershcovitch, A.; Momozaki, Y.; Nolen, J.; Reed, C. & Thieberger, P.
System: The UNT Digital Library
Distinct cinnamoyl CoA reductases involved in parallel routes to lignin in Medicago truncatula (open access)

Distinct cinnamoyl CoA reductases involved in parallel routes to lignin in Medicago truncatula

Article on distinct cinnamoyl CoA reductases involved in parallel routes to lignin in Medicago truncatula.
Date: October 12, 2010
Creator: Zhou, Rui; Jackson, Lisa A.; Shadle, Gail L.; Nakashima, Jin; Temple, Stephen; Chen, Fang et al.
System: The UNT Digital Library
Engineering the Electronic Band Structure for Multiband Solar Cells (open access)

Engineering the Electronic Band Structure for Multiband Solar Cells

Using the unique features of the electronic band structure of GaNxAs1-x alloys, we have designed, fabricated and tested a multiband photovoltaic device. The device demonstrates an optical activity of three energy bands that absorb, and convert into electrical current, the crucial part of the solar spectrum. The performance of the device and measurements of electroluminescence, quantum efficiency and photomodulated reflectivity are analyzed in terms of the Band Anticrossing model of the electronic structure of highly mismatched alloys. The results demonstrate the feasibility of using highly mismatched alloys to engineer the semiconductor energy band structure for specific device applications.
Date: July 12, 2010
Creator: Lopez, N.; Reichertz, L. A.; Yu, K. M.; Campman, K. & Walukiewicz, W.
System: The UNT Digital Library
EUV-multilayers on grating-like topographies (open access)

EUV-multilayers on grating-like topographies

In this study, multilayer morphology near the key anomalies in grating-like structures, namely sharp step-edges and steep walls, are examined. Different deposition schemes are employed. Based on cross section TEM analysis an explanatory model describing the morphology of the successive layers is developed. A further insight into the periodicity and the general performance of the multilayer is obtained by EUV microscopy. The main distortions in multilayer structure and hence EUV performance are found to be restricted to a region within a few hundred nanometers from the anomalies, which is very small compared to the proposed grating period (50-100 {micro}m). These multilayer coated blazed gratings can thus be considered a viable option for spectral purity enhancement of EUV light sources.
Date: March 12, 2010
Creator: van Boogaard, A. J. R.; Louis, E.; Goldberg, K. A.; Mochi, I. & Bijkerk, F.
System: The UNT Digital Library
EUV pattern defect detection sensitivity based on aerial image linewidth measurements (open access)

EUV pattern defect detection sensitivity based on aerial image linewidth measurements

As the quality of EUV-wavelength mask inspection microscopes improves over time, the image properties and intensity profiles of reflected light can be evaluated in ever-greater detail. The SEMATECH Berkeley Actinic Inspection Tool (AIT) is one such microscope, featuring mask resolution values that match or exceed those available through lithographic printing in current photoresists. In order to evaluate the defect detection sensitivity of the AIT for dense line patterns on typical masks, the authors study the line width roughness (LWR) on two masks, as measured in the EUV images. They report the through-focus and pitch dependence of contrast, image log slope, linewidth, and LWR. The AIT currently reaches LWR 3{sigma} values close to 9 nm for 175 nm half-pitch lines. This value is below 10% linewidth for nearly all lines routinely measured in the AIT. Evidence suggests that this lower level may arise from the mask's inherent pattern roughness. While the sensitivity limit of the AlT has not yet been established, it is clear that the AIT has the required sensitivity to detect defects that cause 10% linewidth changes in line sizes of 125 nm and larger.
Date: February 12, 2010
Creator: Goldberg, K. A.; Mochi, I.; Naulleau, P.; Liang, T.; Yan, P.-Y. & Huh, S.
System: The UNT Digital Library
Extension of the Southern Hemisphere Atmospheric Radiocarbon Curve, 2120-850 years BP: Results from Tasmanian Huon Pine (open access)

Extension of the Southern Hemisphere Atmospheric Radiocarbon Curve, 2120-850 years BP: Results from Tasmanian Huon Pine

Decadal samples of dendrochronologically-dated pine (Lagorostrobos franklinii) from the Stanley River basin, Tasmania have been radiocarbon dated between 2120-850 yr BP. This data set overlaps and extends the current Southern Hemisphere record, which currently covers the period 110-995 yr BP. There is good agreement between the two records between 995-850 yr BP, between sample replicates and with consensus values for standards. As in the younger dataset, we find evidence for a distinct but variable offset between the southern hemisphere data and IntCal04; although this is likely due to real temporal variability in the interhemispheric offset, further work is planned to rule out possible laboratory or sample preparation differences.
Date: February 12, 2010
Creator: Zimmerman, S. R.; Guilderson, T. P.; Buckley, B. M. & Cook, E.
System: The UNT Digital Library