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Engineering the Electronic Band Structure for Multiband Solar Cells

Description: 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 electron… more
Date: July 12, 2010
Creator: Lopez, N.; Reichertz, L. A.; Yu, K. M.; Campman, K. & Walukiewicz, W.
Partner: UNT Libraries Government Documents Department
open access

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

Description: 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.… more
Date: May 12, 2010
Creator: Chu, T S; Anderson, S G; Gibson, D J; Hartemann, F V; Marsh, R A; Siders, C et al.
Partner: UNT Libraries Government Documents Department
open access

Hydrogen Bonding Under High-Pressure

Description: No Description Available.
Date: March 12, 2010
Creator: Manaa, M R & Fried, L E
Partner: UNT Libraries Government Documents Department
open access

High Power Picosecond Laser Pulse Recirculation

Description: We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.
Date: April 12, 2010
Creator: Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J et al.
Partner: UNT Libraries Government Documents Department
open access

Magnetic stochasticity in gyrokinetic simulations of plasma microturbulence

Description: Analysis of the magnetic field structure from electromagnetic simulations of tokamak ion temperature gradient turbulence demonstrates that the magnetic field can be stochastic even at very low plasma pressure. The degree of magnetic stochasticity is quantified by evaluating the magnetic diffusion coefficient. We find that the magnetic stochasticity fails to produce a dramatic increase in the electron heat conductivity because the magnetic diffusion coefficient remains small.
Date: February 12, 2010
Creator: Nevins, W M; Wang, E & Candy, J
Partner: UNT Libraries Government Documents Department
open access

Target Diagnostic Control System Implementation for the National Ignition Facility

Description: The extreme physics of targets shocked by NIF's 192-beam laser are observed by a diverse suite of diagnostics. Many diagnostics are being developed by collaborators at other sites, but ad hoc controls could lead to unreliable and costly operations. A Diagnostic Control System (DCS) framework for both hardware and software facilitates development and eases integration. Each complex diagnostic typically uses an ensemble of electronic instruments attached to sensors, digitizers, cameras, and other… more
Date: May 12, 2010
Creator: Shelton, R T; Kamperschroer, J H; Lagin, L J; Nelson, J R & O'Brien, D W
Partner: UNT Libraries Government Documents Department
open access

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

Description: 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 exceedi… more
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.
Partner: UNT Libraries Government Documents Department
open access

Scaling Algebraic Multigrid Solvers: On the Road to Exascale

Description: Algebraic Multigrid (AMG) solvers are an essential component of many large-scale scientific simulation codes. Their continued numerical scalability and efficient implementation is critical for preparing these codes for exascale. Our experiences on modern multi-core machines show that significant challenges must be addressed for AMG to perform well on such machines. We discuss our experiences and describe the techniques we have used to overcome scalability challenges for AMG on hybrid architectu… more
Date: December 12, 2010
Creator: Baker, A H; Falgout, R D; Gamblin, T; Kolev, T; Schulz, M & Yang, U M
Partner: UNT Libraries Government Documents Department
open access

Commissioning of the EBIS-based heavy ion preinjector at Brookhaven

Description: 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 spe… more
Date: September 12, 2010
Creator: Alessi, J.; Beebe, E.; Binello, S.; Hoff, L.; Kondo, K.; Lambiase, R. et al.
Partner: UNT Libraries Government Documents Department
open access

Nanoscale Advances in Catalysis and Energy Applications

Description: In this perspective, we present an overview of nanoscience applications in catalysis, energy conversion, and energy conservation technologies. We discuss how novel physical and chemical properties of nanomaterials can be applied and engineered to meet the advanced material requirements in the new generation of chemical and energy conversion devices. We highlight some of the latest advances in these nanotechnologies and provide an outlook at the major challenges for further developments.
Date: May 12, 2010
Creator: Li, Yimin & Somorjai, Gabor A.
Partner: UNT Libraries Government Documents Department
open access

Low and High Temperature Combustion Chemistry of Butanol Isomers in Premixed Flames and Autoignition Systems

Description: Butanol is a fuel that has been proposed as a bio-derived alternative to conventional petroleum derived fuels. The structural isomer in traditional 'bio-butanol' fuel is n-butanol, but newer conversion technologies produce iso-butanol as a fuel. In order to better understand the combustion chemistry of bio-butanol, this study presents a comprehensive chemical kinetic model for all the four isomers of butanol (e.g., 1-, 2-, iso- and tert-butanol). The proposed model includes detailed high temper… more
Date: December 12, 2010
Creator: Sarathy, S M; Pitz, W J; Westbrook, C K; Mehl, M; Yasunaga, K; Curran, H J et al.
Partner: UNT Libraries Government Documents Department
open access

Near-Infrared Localized Surface Plasmon Resonances Arising from Free Carriers in Doped Quantum Dots

Description: Quantum confinement of electronic wavefunctions in semiconductor quantum dots (QDs) yields discrete atom-like and tunable electronic levels, thereby allowing the engineering of excitation and emission spectra. Metal nanoparticles, on the other hand, display strong resonant interactions with light from localized surface plasmon resonance (LSPR) oscillations of free carriers, resulting in enhanced and geometrically tunable absorption and scattering resonances. The complementary attributes of thes… more
Date: October 12, 2010
Creator: Jain, Prashant K.; Luther, Joey; Ewers, Trevor & Alivisatos, A. Paul
Partner: UNT Libraries Government Documents Department
open access

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

Description: 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 o… more
Date: May 12, 2010
Creator: Cone, K. V.; Dunn, J.; Schneider, M. B.; Baldis, H. A.; Brown, G. V.; Emig, J. et al.
Partner: UNT Libraries Government Documents Department
open access

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

Description: 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 vari… more
Date: February 12, 2010
Creator: Zimmerman, S. R.; Guilderson, T. P.; Buckley, B. M. & Cook, E.
Partner: UNT Libraries Government Documents Department
open access

INNOVATIVE ALARA TOOLS AND WORK PRACTICES USED AT THE DOE HANFORD SITE

Description: The Hanford Nuclear Reservation occupies an area of 586 square miles in southeastern Washington state. The site was created as part of the World War II Manhattan Project to produce weapons grade plutonium. A multitude of old reactor plants, processing facilities, underground tank farms, contaminated soil and ground water remain and are part of an on-going environmental cleanup mission of the site. The Columbia River bisects Hanford, and the concern is that the river will become contaminated if … more
Date: February 12, 2010
Creator: LO, WAGGONER
Partner: UNT Libraries Government Documents Department
open access

Thermodynamic States in Explosion Fields

Description: We investigate the thermodynamic states occurring in explosion fields from condensed explosive charges. These states are often modeled with a Jones-Wilkins-Lee (JWL) function. However, the JWL function is not a Fundamental Equation of Thermodynamics, and therefore cannot give a complete specification of such states. We use the Cheetah code of Fried to study the loci of states of the expanded detonation products gases from C-4 charges, and their combustion products air. In the Le Chatelier Plane… more
Date: March 12, 2010
Creator: Kuhl, A L
Partner: UNT Libraries Government Documents Department
open access

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

Description: 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 pro… more
Date: January 12, 2010
Creator: Sharma, A. K.; Smedley, J.; Tsang, T. & Rao, T.
Partner: UNT Libraries Government Documents Department
open access

High-Order Weno Simulations of Three-Dimensional Reshocked Richtmyer-Meshkov Instability to Late Times: Dynamics, Dependence on Initial Conditions, and Comparisons to Experimental Data

Description: The dynamics of the reshocked multi-mode Richtmyer-Meshkov instability is investigated using 513 x 257{sup 2} three-dimensional ninth-order weighted essentially nonoscillatory shock-capturing simulations. A two-mode initial perturbation with superposed random noise is used to model the Mach 1.5 air/SF{sub 6} Vetter-Sturtevant shock tube experiment. The mass fraction and enstrophy isosurfaces, and density cross-sections are utilized to show the detailed flow structure before, during, and after r… more
Date: January 12, 2010
Creator: Schilling, O & Latini, M
Partner: UNT Libraries Government Documents Department
open access

Applications of Laser and Synchrotron Based ARPES to Photocathode Research

Description: 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 a… more
Date: October 12, 2010
Creator: Rameau, J.; Smedley. J.; Muller, E.; Kidd, T.; Johnson, P.; Allen, P. et al.
Partner: UNT Libraries Government Documents Department
open access

Challenges of Algebraic Multigrid across Multicore Architectures

Description: 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 (H… more
Date: April 12, 2010
Creator: Baker, A H; Gamblin, T; Schulz, M & Yang, U M
Partner: UNT Libraries Government Documents Department
open access

SINGLE-MODE FIBER, VELOCITY INTERFEROMETRY

Description: No Description Available.
Date: December 12, 2010
Creator: Krauter, K. G.; Jacobson, G. F.; Patterson, J. R.; Nguyen, J. H. & Ambrose, W. P.
Partner: UNT Libraries Government Documents Department
open access

Transient Heat Transfer Analysis for Ion-Exchange Waste Removal Process

Description: The small column ion exchange (SCIX) process treats low curie salt (LCS) waste before feeding it to the saltstone facility to be made into grout. Through this process, radioactive cesium from the salt solution is absorbed into the CST bed. A CST column loaded with radioactive cesium will generate significant heat from radiolytic decay. If engineering designs of the CST sorption column can not handle this thermal load, hot spots may develop locally within the column and degrade the performance o… more
Date: July 12, 2010
Creator: Lee, S.
Partner: UNT Libraries Government Documents Department
open access

Study of multi-muon events produced in p anti-p interactions at s**(1/2) = 1.96-TeV

Description: We report the results of a study of multi-muon events produced at the Fermilab Tevatron collider and acquired with the CDF II detector using a dedicated dimuon trigger. The production cross section and kinematics of events in which both muon candidates are produced inside the beam pipe of radius 1.5 cm are successfully modeled by known processes which include heavy flavor production. In contrast, we are presently unable to fully account for the number and properties of the remaining events, in … more
Date: June 12, 2010
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Adelman, J.; /Chicago U., EFI; Alvarez Gonzalez, B.; Phys., /Cantabria Inst. of et al.
Partner: UNT Libraries Government Documents Department
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