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in subjects: "Charge Density"

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Relativistic effects in the atomic and nuclear few-body problems

Relativistic effects in the atomic and nuclear few-body systems are classified and discussed with the emphasis on electromagnetic transitions. The size of relativistic corrections, calculational techniques and ambiguities, and comparison of theory and experiment are considered. 8 figures.

Date: January 1, 1980

Creator: Friar, J.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Microscopic theory of charges density wave instability in NbSe/sub 2/

The microscopic theory of Sinha and Harmon for electronically driven lattice instabilities is used to explain the ''Kohn-like'' anomalies in the ..sigma../sub 1/ phonon branch and the observed incommensurate superlattice Bragg peak in 2H-NbSe/sub 2/, characteristic of the charge density wave at low temperatures in the neutron scattering experiments of Moncton et al. In accordance with the APW and LCAO band-structure calculations of Mattheiss of 2H-NbSe/sub 2/, the presence o… more

Date: January 1, 1977

Creator: Das, S G; Sinha, S K & Wakabayashi, N

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Solid electrolytes and impact-resistant ceramics

In this proposal, we describe a program to exploit recent achievements in two distinct areas of materials science, both of them dependent on the independent motion of singly charged ions through an immobile matrix. The first is the area of non-crystalline solid electrolytes in which this laboratory has gained prominence over the past decade. The second is an area proposed for study in our previous proposal and now verified as a principle worthy of considerable further investigation: it involves… more

Date: August 1991

Creator: Angell, C. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

X-ray scattering studies of non-equilibrium ordering processes

This report summarizes the major results obtained under US DOE Grant Number FG05-90ER45280 from the dates November 1, 1989 through October 31, 1992 inclusive. The principal work includes x-ray scattering studies of phase transition kinetics in binary alloy order-disorder transitions, block co-polymer crystallization, and charge density wave solids under applied electric fields, and studies of magnetic excitations in low dimensional quantum systems.

Date: January 1, 1992

Creator: Nagler, S.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Parameter scaling to produce different charged-particle beam-transport systems having identical equations of motion

Designs are freuently required for charged-particle optics channels to transport space-charge (Coulomb) force-dominated beams for use with accelerators under design or construction. It is often desirable to experimentally test a design using an existing accelerator having different parameters from the one under consideration. This paper shows how to scale a charged-particle transport design to make a model experiment for testing the design with an existing accelerator. Sometimes, with the prope… more

Date: April 1, 1988

Creator: Wadlinger, E.A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Large scale calculations of the structure and dynamics of dense matter

The physics of matter at high density has been found to be strongly influenced by transient quasi-molecular phenomena, the distribution of electron charge density among several nearby atoms. Calculations performed using the self-consistent field molecular dynamics approximation, a synthesis of techniques derived from quantum chemistry and molecular dynamics, have shown that such effects can result in more than a 30% increase in the diffusion coefficient of helium at 1 g/cc. The effect of finite… more

Date: January 1, 1989

Creator: Younger, S.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Interacting boson model and medium energy probes

Medium energy electron and proton scattering are used to determine the quadrupole form factors for the Interacting Boson Model of Nuclei. 12 refs., 3 figs.

Date: January 1, 1986

Creator: Ginocchio, J.N. & Wenes, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Computational and Spectroscopic Investigations of the Molecular Scale Structure and Dynamics of Geologically Important Fluids and Mineral-Fluid Interfaces

Research supported by this grant focuses on molecular scale understanding of central issues related to the structure and dynamics of geochemically important fluids, fluid-mineral interfaces, and confined fluids using computational modeling and experimental methods. Molecular scale knowledge about fluid structure and dynamics, how these are affected by mineral surfaces and molecular-scale (nano-) confinement, and how water molecules and dissolved species interact with surfaces is essential to un… more

Date: November 25, 2008

Creator: Kirkpatrick, R. James & Kalinichev, Andrey G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Where Water is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster from X-ray Spectroscopy

Light-driven oxidation of water to dioxygen in plants, algae and cyanobacteria iscatalyzed within photosystem II (PS II) by a Mn4Ca cluster. Although the cluster has been studied by many different methods, the structure and the mechanism have remained elusive. X-ray absorption and emission spectroscopy and EXAFS studies have been particularly useful in probing the electronic and geometric structure, and the mechanism of the water oxidation reaction. Recent progress, reviewed here, includes pola… more

Date: October 24, 2007

Creator: Yano, Junko; Yano, Junko & Yachandra, Vittal K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Numerical Study of Coulomb Scattering Effects on Electron Beamfrom a Nano-Tip

Nano-tips with high acceleration gradient around the emission surface have been proposed to generate high brightness beams. However, due to the small size of the tip, the charge density near the tip is very high even for a small number of electrons. The stochastic Coulomb scattering near the tip can degrade the beam quality and cause extra emittance growth and energy spread. In the paper, we present a numerical study of these effects using a direct relativistic N-body model. We found that emitt… more

Date: June 25, 2007

Creator: Qiang, Ji; Corlett, John N.; Lidia, Steven M.; Padmore, HowardA.; Wan, Weishi; Zholent, Andrew A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Design of an electro-optical sampling experiment at the AWA facility

The free space electro-optical (EO) sampling technique is a powerful tool for analyzing the longitudinal charge density of an ultrashort e-beam. In this paper, we present (1) experimental results for a laser-based mock-up of the EO experiment [1] and (2) a design for a beam-based, single-shot, EO sampling experiment using the e-beam from the Argonne Wakefield Accelerator (AWA) RF photoinjector. For the mock-up, a tabletop terahertz experiment is conducted in the AWA laser room. The mock-up uses… more

Date: June 1, 2007

Creator: Ruan, J.; Edwards, H.; Tan, Cheng Yang; Thurman-Keup, R.; Scarpine, V.; /Fermilab et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

ARPES study of the evolution of band structure and charge density wave properties in RTe3 ( R=Y , La, Ce, Sm, Gd, Tb, and Dy)

We present a detailed angle-resolved photoemission spectroscopy (ARPES) investigation of the RTe3 family, which sets this system as an ideal"textbook" example for the formation of a nesting driven charge density wave (CDW). This family indeed exhibits the full range of phenomena that can be associated to CDWinstabilities, from the opening of large gaps on the best nested parts of Fermi surface (up to 0.4 eV), to the existence of residual metallic pockets. ARPES is the best suited tech… more

Date: January 16, 2008

Creator: Hussain, Zahid; Brouet, Veronique; Yang, Wanli; Zhou, Xingjiang; Hussain, Zahid; Moore, R. G. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development of a 2D Vlasov Solver for Single-Pass Systems

Direct numerical methods for solving the Vlasov equationoffer some advantages over macroparticle simulations, as they do notsuffer from the numerical noise inherent in using a number ofmacroparticles smaller than the bunch population. Unfortunately thesemethods are more time-consuming and generally considered impractical in afull 6D phase space. However, in a lower-dimension phase space they maybecome attractive if the beam dynamics is sensitive to the presence ofsmall charge-density fluctuatio… more

Date: July 31, 2006

Creator: Venturini, Marco; Warnock, Robert & Zholents, Alexander

Item Type: Report

Partner: UNT Libraries Government Documents Department

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A Vlasov Solver for Longitudinal Dynamics in Beam Delivery Systems for X-Ray FELs

Direct numerical methods for solving the Vlasov equationoffer some advantages over macroparticle simulations, as they do notsuffer from the consequences of the statistical fluctuations inherent inusing a number of macroparticles smaller than thebunch population.Unfortunately these methods are more time-consuming and generallyconsidered impractical in a full 6D phase space. However, in alower-dimension phase space they may become attractive if the beamdynamics is sensitive to the presence of sma… more

Date: May 9, 2007

Creator: Venturini, Marco; Warnock, Robert & Zholents, Alexander

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Error-Induced Beam Degradation in Fermilab's Accelerators

In Part I, three independent models of Fermilab's Booster synchrotron are presented. All three models are constructed to investigate and explore the effects of unavoidable machine errors on a proton beam under the influence of space-charge effects. The first is a stochastic noise model. Electric current fluctuations arising from power supplies are ubiquitous and unavoidable and are a source of instabilities in accelerators of all types. A new noise module for generating the Ornstein-Uhlenbeck (… more

Date: August 1, 2007

Creator: Yoon, Phil S.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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Revealing Charge Density Wave Formation in the LaTe2 System byAngle Resolved Photoemission Spectroscopy

We present the first direct study of charge density wave(CDW) formation in quasi-2D single layer LaTe2 using high-resolutionangle resolved photoemission spectroscopy (ARPES) and low energy electrondiffraction (LEED). CDW formation is driven by Fermi surface (FS)nesting, however characterized by a surprisingly smaller gap (~;50 meV)than seen in the double layer RTe3 compounds, extending over the entireFS. This establishes LaTe2 as the first reported semiconducting 2D CDWsystem where the CDW phas… more

Date: November 15, 2006

Creator: Garcia, D. R.; Gweon, G.-H.; Zhou, S. Y.; Graf, J.; Jozwiak, C. M.; Jung, M. H. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A FOUR-DIMENSIONAL VLASOV SOLVER FOR MICROBUNCHING INSTABILITY INTHE INJECTION SYSTEM FOR X-RAY FELS

The micro-bunching instability (MBI) is seeded by small charge-density fluctuations in the electron bunches, and is successively amplified by the combined effect of space charge and coherent synchrotron radiation, as the beam travels through magnetic compressors. The quantitative understanding of this effect demands for accurate numerical simulations. Here we report on the progress of an upgrading of a 2D Vlasov solver code toward a 4D grid-based Vlasov solver, including also the transversedyna… more

Date: June 23, 2008

Creator: Venturini, Marco; Migliorati, Mauro; Schiavi, Angelo; Dattoli, Giuseppe & Venturini, Marco

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electrochemical arsenic remediation for rural Bangladesh

Arsenic in drinking water is a major public health problem threatening the lives of over 140 million people worldwide. In Bangladesh alone, up to 57 million people drink arsenic-laden water from shallow wells. ElectroChemical Arsenic Remediation(ECAR) overcomes many of the obstacles that plague current technologies and can be used affordably and on a small-scale, allowing for rapid dissemination into Bangladesh to address this arsenic crisis. In this work, ECAR was shown to effectively reduce 5… more

Date: January 1, 2009

Creator: Addy, Susan Amrose

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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The glasma initial state and JIMWLK factorization

We review recent work on understanding the next to leading order corrections to the classical fields that dominate the initial stages of a heavy ion collision. We have recently shown that the leading ln 1/x divergences of these corrections to gluon multiplicities can be factorized into the JIMWLK evolution of the color charge density distributions.

Date: August 26, 2008

Creator: Gelis, F.; Lappi, T. & Venugopalan, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

PetaScale calculations of the electronic structures ofnanostructures with hundreds of thousands of processors

Density functional theory (DFT) is the most widely used ab initio method in material simulations. It accounts for 75% of the NERSC allocation time in the material science category. The DFT can be used to calculate the electronic structure, the charge density, the total energy and the atomic forces of a material system. With the advance of the HPC power and new algorithms, DFT can now be used to study thousand atom systems in some limited ways (e.g, a single selfconsistent calculation without at… more

Date: April 1, 2006

Creator: Wang, Lin-Wang; Zhao, Zhengji & Meza, Juan

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Probing the band structure of LaTe2 using angle resolved photoemission spectroscopy

With the current interest in the rare-earth tellurides ashigh temperature charge density wave materials, a greater understandingof the physics of these systems is needed, particularly in the case ofthe ditellurides. We report a detailed study of the band structure ofLaTe_2 in the charge density wave state using high-resolution angleresolved photoemission spectroscopy (ARPES). From thiswork we hope toprovide insights into the successes and weaknesses of past theoreticalstudy as well as helping t… more

Date: November 1, 2006

Creator: Garcia, Daniel R.; Zhou, Shuyun Y.; Gweon, Gey-Hong; Jung, M.H.; Kwon, Y.S. & Lanzara, Alessandra

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A 3D Model for Ion Beam Formation and Transport Simulation

In this paper, we present a three-dimensional model forself-consistently modeling ion beam formation from plasma ion sources andtransporting in low energy beam transport systems. A multi-sectionoverlapped computational domain has been used to break the originaltransport system into a number of weakly coupled subsystems. Within eachsubsystem, macro-particle tracking is used to obtain the charge densitydistribution in this subdomain. The three-dimensional Poisson equation issolved within the subd… more

Date: February 7, 2006

Creator: Qiang, J.; Todd, D. & Leitner, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development of Carbon Based optically Transparent Electrodes from Pyrolyzed Photoresist for the Investigation of Phenomena at Electrified Carbon-Solution Interfaces

The work presented herein describes a fundamental investigations of carbon as electrode material by using the pyrolysis of photoresist to create an optically transparent material. The development of these carbon-based optically transparent electrodes (C-OTEs) enables investigations of molecular interactions within the electrical double layer, processes that are central to a wide range of important phenomena, including the impact of changes in the surface charge density on adsorption. The electr… more

Date: December 1, 2007

Creator: Donner, Sebastian

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Self Consistent Monte Carlo Method to Study CSR Effects in Bunch Compressors

In this paper we report on the results of a self-consistent calculation of CSR effects on a particle bunch moving through the benchmark Zeuthen bunch compressors. The theoretical framework is based on a 4D Vlasov-Maxwell approach including shielding from the vacuum chamber. We calculate the fields in the lab frame, where time is the independent variable, and evolve the phase space density/points in the beam frame, where arc length, s, along a reference orbit, is the independent variable. Some d… more

Date: January 8, 2008

Creator: Warnock, R. L.; Bassi, G.; Ellison, J. A. & Heinemann, K. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department