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in creator/contributor: "Wang, L."

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Poisson Solver with Floating Conductor Implementation in REMCOM XFDTD Software, Benchmark Calculation Examples

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Date: December 20, 2012

Creator: Poole, B. R. & Wang, L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Study on the Volumetric Ratio of the Hybrid Gm Regenerator Over the Cold Chamber Working at 4k.

This paper presents a computational analysis on the hybrid GM regenerator at liquid helium region. The effects of the ratio of the regenerator volume over the cold chamber volume on cooling performance were simulated numerically. The results show that there exits a minimum ratio of the regenerator volume over the cold chamber volume for a G-M cryocooler at 4K. The cooling capacity of the refrigerator drops sharply with smaller regenerator, and rises slowly with larger regenerator. The effects o… more

Date: July 12, 1999

Creator: Wang, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Quark-diagram classification of charm decays

The decays of charm mesons are described in terms of quark-diagram amplitudes. Experimental implications of these amplitudes are also discussed.

Date: May 1, 1980

Creator: Rizzo, T. G. & Wang, L. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Temperature dependence of ion-beam-induced amorphization in {beta}-SiC

The ion-beam-induced crystalline-to-amorphous transition in monolithic {beta}-SIC has been studied as a function of irradiation temperature using the HVEM-Tandem Facility at Argonne National Laboratory. Specimens were irradiated with 1.5 MeV Xe{sup +} ions over the temperature range from 40 to 550 K, and the evolution of the amorphous state was followed in situ using the HVEM. At 40 K, the displacement dose for complete amorphization in {beta}-SIC is 0.34 dpa and increases with temperature in t… more

Date: February 1, 1995

Creator: Weber, W. J. & Wang, L. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Stability of Uranium Silicides During High Energy Ion Irradiation

Changes induced by 1.5 MeV Kr ion irradiation of both U{sub 3}Si and U{sub 3}Si{sub 2} have been followed by in situ transmission electron microscopy. When irradiated at sufficiently low temperatures, both alloys transform from the crystalline to the amorphous state. When irradiated at temperatures above the temperature limit for ion beam amorphization, both compounds disorder with the Martensite twin structure in U{sub 3}Si disappearing from view in TEM. Prolonged irradiation of the disordered… more

Date: November 1, 1991

Creator: Birtcher, R. C & Wang, L. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Defects in Photovoltaic Materials and the Origins of Failure to Dope Them: Preprint

I will review the basic physical principles underlying the formation energy of various intrinsic defects in common photovoltaic materials. I then use the above principles to explain why doping of semiconductors is, in general, limited and which design principles can be used to circumvent such limits. This work can help design strategies of doping absorber materials as well as explain how TCOs work. Recent results on the surprising stability of polar (112)+ surfaces of CIS will also be described… more

Date: May 1, 2002

Creator: Zunger, A.; Kilic, C. & Wang, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ion Effects in the Electron Damping Ring of the International Linear Collider

Ion-induced beam instabilities and tune shifts are critical issues for the electron damping ring of the International Linear Collider (ILC). To avoid conventional ion trapping, a long gap is introduced in the electron beam by omitting a number of successive bunches out of a long train. However, the beam can still suffer from the fast ion instability, driven by ions that last only for a single passage of the electron bunches. Our study shows that the ion effects can be significantly mitigated by… more

Date: July 17, 2006

Creator: Wang, L.; Raubenheimer, T. & Wolski, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Simulation of the Beam-Ion Instability in the Electron Damping Ring of the International Linear Collider

Ion induced beam instability is one critical issue for the electron damping ring of the International Linear Collider (ILC) due to its ultra small emittance of 2pm. Bunch train filling pattern is proposed to mitigate the instability and bunch-by-bunch feedback is applied to suppress it. Multibunch train fill pattern is introduced in the electron beam to reduce the number of trapped ions. Our study shows that the ion effects can be significantly mitigated by using multiple gaps. However, the bea… more

Date: July 6, 2007

Creator: Wang, L.; Cai, Y. & Raubenheimer, T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effect of temperature and recoil-energy spectra on irradiation-induced amorphization in Ca{sub 2}La{sub 8}(SiO{sub 4}){sub 6}O{sub 2}

Single crystals of Ca{sub 2}La{sub 8}(SiO{sub 4}){sub 6}O{sub 2} have been irradiated with different ions/energies in an in situ study of the effects of temperature and recoil-energy spectra on irradiation-induced amorphization. The dose for complete amorphization increases with temperature in two stages. The low-temperature stage (below 250 K) has an activation energy of 0.01 {plus_minus} 0.003 eV and is believed to be associated with simultaneous close-pair recombination. The high-temperature… more

Date: September 1, 1993

Creator: Weber, W. J. & Wang, L. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Characterization of collision cascade damage in Ca{sub 2}La{sub 8}(SiO{sub 4}){sub 6}O{sub 2} by HRTEM

Ca{sub 2}La{sub 8}(SiO{sub 4}){sub 6}O{sub 2} thin crystals become amorphous under ion beam irradiation. The ion dose required for complete amorphization of the thin crystal (critical amorphization dose, D{sub c}) increased with the increasing irradiation temperature and decreased with ion mass at elevated temperatures. Samples irradiated with 1-1.5 MeV Ar{sup +}, Kr{sup +} and Xe{sup +} ions to doses much lower than Dc, in the temperature range from 20 to 498 K were used for a detailed HRTEM s… more

Date: December 1, 1994

Creator: Weber, W. J. & Wang, L. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Design and Simulation of an Anode Stalk Support Insulator

An anode stalk support insulator in a magnetically insulated transmission line was designed and modeled. One of the important design criteria is that within space constraints, the electric field along the insulator surface has to be minimized in order to prevent a surface flashover. In order to further reduce the field on the insulator surface, metal rings between insulator layers were also specially shaped. To facilitate the design process, electric field simulations were performed to determin… more

Date: May 16, 2005

Creator: Wang, L.; Houck, T. & Westenskow, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electron Coud Dynamics in High-Intensity Rings.

Electron cloud due to beam-induced multipacting is one of the main concerns for the high intensity. Electrons generated and accumulated inside the beam pipe form an ''electron cloud'' that interacts with the circulating charged particle beam. With sizeable amount of electrons, this interaction can cause beam instability, beam loss and emittance growth. At the same time, the vacuum pressure will rise due to electron desorption. This talk intends to provide an overview of the mechanism and dynami… more

Date: May 16, 2005

Creator: Wang, L. & Wei, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Precise Calculation of Traveling-Wave Periodic Structure

The effects of the round edge beam hole on the frequency and wake field are studied using variational method, which allows for rounded iris disk hole without any approximation in shape treatment. The frequency and wake field of accelerating mode and dipole mode are studied for different edge radius cases, including the flat edge shape that is often used to approximately represent the actual structure geometry. The edge hole shape has weak effect on the frequency, but much effect on the wake fie… more

Date: July 6, 2007

Creator: Wang, L.; Li, Z. & Seryi, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Stability of uranium silicides during high energy ion irradiation

Date: November 1, 1991

Creator: Birtcher, R. C. & Wang, L. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Distortion of Crabbed Bunch Due to Electron Cloud and Global Crabbing

Crab cavities may be used improve the luminosity in colliding beam colliders with crab crossing. In a global crab crossing correction, only one crab cavity is installed in each ring and the crab cavities generate a horizontally titled bunch oscillating around the ring. The electron cloud in positively charged rings may distort the crabbed bunch and cause the luminosity drop. This paper briefly estimates the distortion of positron bunch due to the electron cloud with global crab and estimates th… more

Date: August 1, 2008

Creator: Wang, L.; Raubenheimer, T.O. & Cai, Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Suppression of Secondary Emission in a Magnetic Field Using a Sawtooth and Isosceles Triangle Surface

The effect of surface roughness on the secondary electron emission from a sawtooth and isosceles triangle surface in a magnetic field under electron bombardment is investigated using a Monte-Carlo method. Some of the secondary electrons emitted from the surface return to the surface within their first few gyrations, resulting in a low effective secondary electron yield. Both sawtooth and isosceles triangle surface in magnetic field can significantly reduce the secondary emission yield below the… more

Date: September 26, 2006

Creator: Wang, L.; Raubenheimer, T.O. & Stupakov, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nonlinear Gyrokinetic Theory With Polarization Drift

A set of the electrostatic toroidal gyrokinetic Vlasov equation and the Poisson equation, which explicitly includes the polarization drift, is derived systematically by using Lie-transform method. The polarization drift is introduced in the gyrocenter equations of motion, and the corresponding polarization density is derived. Contrary to the wide-spread expectation, the inclusion of the polarization drift in the gyrocenter equations of motion does not affect the expression for the polarization … more

Date: March 25, 2010

Creator: Wang, L. & Hahm, T. S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Thermal Uniformity of Liquid Helium in Electron Bubble Chamber.

A CRYOGENIC RESEARCH APPARATUS TO MEASURE THE MOVEMENT OF ELECTRONS UNDER A HIGH ELECTRIC FIELD IN A LIQUID HELIUM BATH WAS DESIGNED AND BUILT AT THE BROOKHAVEN NATIONAL LABORATORY AND THE NEVIS LABORATORY OF COLUMBIA UNIVERSITY. THE LIQUID HELIUM CHAMBER IS A DOUBLE WALLED CYLINDRICAL CONTAINER EQUIPPED WITH 5 OPTICS WINDOWS AND 10 HIGH VOLTAGE CABLES. TO SHIELD THE LIQUID HELIUM CHAMBER AGAINST THE EXTERNAL HEAT LOADS AND TO PROVIDE THE THERMAL UNIFORMITY IN THE LIQUID HELIUM CHAMBER, THE DOU… more

Date: July 22, 2002

Creator: Wang, L. & Jia, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Radiation-Induced Decomposition of U(VI) Phase to Nanocrystals of UO2

U{sup 6+}-phases are common alteration products, under oxidizing conditions, of uraninite and the UO{sub 2} in spent nuclear fuel. These U{sup 6+}-phases are subjected to a radiation field caused by the {alpha}-decay of U, or in the case of spent nuclear fuel, incorporated actinides, such as {sup 239}Pu and {sup 237}Np. In order to evaluate the effects of {alpha}-decay events on the stability of the U{sup 6+}-phases, we report, for the first time, the results of ion beam irradiations (1.0 MeV K… more

Date: January 28, 2005

Creator: Utsunomiya, S.; Ewing, R. C. & Wang, L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Radiation Effects on the Sorption and Mobilization of Radionuclide during Transport through the Geosphere

Site restoration activities at DOE facilities and the permanent disposal of nuclear waste inevitably involve understanding the behavior of materials in a radiation field. Radionuclide decay and the associated radiation fields lead to physical and chemical changes that can degrade or enhance important material properties. Alpha-decay of the actinide elements and beta-decay of the fission products lead to atomic-scale changes in materials (radiation damage and transmutation).

Date: March 14, 2004

Creator: Wang, L.M.; Eqing, R.C. & Hayes, K.F.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Probing nano-defects in fused silica by near-field scanning optical microscopy

Nanodefects were artificially introduced into fused silica surface by nano-indenting with a commercial atomic force microscope (AFM). The sample was illuminated at total internal refkction configuration and evanescent waves were detected by near-field scanning optical probe in the constant tip-sample separation mode. The strain fields associated with non-indents were attributed to the contrast mechanism in optical images. Thus the optical image directly maps out the strain distributions associa… more

Date: March 17, 1998

Creator: Wang, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Extending the class of order-k delineable problems for the gene expression messy genetic algorithm

This paper revisits the recently introduced gene expression messy genetic algorithm (GEMGA) and offers some modifications to the extend the class of order-k delineable problems (class of problems that can be solved using a bounded order of relations) in GEMGA. The fundamental components that control the delineability of relations are reviewed in the light of the recently proposed SEARCH framework. Modified class and relation comparison statistics of GEMGA are proposed. The sample complexity of … more

Date: October 1, 1996

Creator: Kargupta, H.; Goldberg, D.E. & Wang, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Novel Approach to Materials Development for Advanced Reactor Systems - Quarterly Progress Report: Year 2; Quarter 1

OAK B188 A Novel Approach to Materials Development for Advanced Reactor Systems - Quarterly Progress Report: Year 2; Quarter 1. There are three major goals for year two of the program. First, to build on the successful initial experiments on proton irradiation of pressure vessel steel to expand the irradiations to study dose rate and temperature effects, radiation effects on commercial alloys and to better characterize the precipitates. Second, we will begin irradiation and characterization of … more

Date: June 25, 2002

Creator: Was, G. S.; Atzmon, M. & Wang, L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

A Novel Approach to Materials Development for Advanced Reactor Systems. Annual Report for Year 1

OAK B188 A Novel Approach to Materials Development for Advanced Reactor Systems. Annual Report for Year 1 Year one of this project had three major goals. First, to specify, order and install a new high current ion source for more rapid and stable proton irradiation. Second, to assess the use of chromium pre-enrichment and the combination of cold-work and irradiation hardening in an effort to assess the role of radiation damage in IASCC without the effects of RIS. Third, to initiate irradiation … more

Date: September 28, 2000

Creator: Was, G.S.; Atzmon, M. & Wang, L.

Item Type: Report

Partner: UNT Libraries Government Documents Department