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Status report on the long-term stability of the Advanced Photon Source.

Description: Table 1 summarizes the average elevation changes and standard deviations as well as the points with the largest changes for each year. On average, hardly any settlements can be detected; however, local changes of +2.90 mm to {minus}2.31 mm have been measured. Looking at the low and high points, the settlement process is slowing down over time. Overall, the settlements observed match the expectations for this type of construction. To date no major realignment of the Advanced Photon Source (APS) storage ring has been necessary. The particle beam tracks with the settlements of the floor as long as these changes occur in a smooth fashion and not as sudden discontinuities [5]. From Figures 6 through 8 it is also apparent that settlements affect larger areas in the storage ring and experiment hall that impact the location of the source point as well as the location of the beamline user equipment. The limiting apertures of the insertion device chambers will make realignment of the APS storage ring a necessity at some point in the future. Currently simulations and machine studies we underway to provide an estimate of tolerable settlement limits before a realignment of certain sections of the storage ring would be required. In conclusion, the APS has been constructed on solid ground with an excellent foundation. Only small settlement changes are being observed; so far they are not impacting the operation of the accelerator. We are continuing to monitor deformations of the APS floor in anticipation of a future realignment of the accelerator components.
Date: September 21, 1998
Creator: Friedsam, H.
Partner: UNT Libraries Government Documents Department

Synchrotron radiation issues in future hadron colliders

Description: Hadron machines mostly use high field superconducting magnets operating at low temperatures. Therefore the issue of extracting a SR power heat load becomes more critical and costly. Conceptual solutions to the problem exist in the form of beam screens and photon stops. Cooled beam screens are more expensive in production and operation than photon stops, but they are, unlike photon stops, routinely used in existing machines. Photon stops are the most economical solution because the heat load is extracted at room temperature. They presently consider it most prudent to work with a combined beam screen and photon stop approach, in which the photon stop absorbs most of the SR power, and the beam screen serves only the vacuum purpose. Provided that the recently launched photon stop R and D [10] supports it, we would like to explore solutions with photon stops only. This would allow to reduce the magnet apertures to a certain extent with respect to those required to accommodate high SR power compliant beam screens and reduce cost. The possibility of magnet designs, which have larger vertical apertures where large cooling capillaries can be housed at no additional cost, would allow to soften this statement somewhat and should therefore be pursued as well.
Date: November 21, 2002
Creator: Bauer, P.; Darve, C. & Terechkine, I.
Partner: UNT Libraries Government Documents Department


Description: A precision measurement of the anomalous g value, a{sub {mu}}=(g-2)/2, for the positive muon has been made using high intensity protons available at the Brookhaven AGS. The result based on the 1999 data a{sub {mu}}=11659202(14)(6) x 10{sup 10} (1.3ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The current theoretical value from the standard model is a{sub {mu}} (SM)=11659159.6(6.7) x 10{sup 10} (0.57 ppm) and differ by over 2.5 standard deviation with experiment. Issues with reducing systematic errors and enhancing the injection and storage efficiencies are discussed.
Date: September 21, 2001
Partner: UNT Libraries Government Documents Department

Optics Elements for Modeling Electrostatic Lenses and Accelerator Components: III. Electrostatic Deflectors

Description: Ion-beam optics models for simulating electrostatic prisms (deflectors) of different geometries have been developed for the computer code TRACE 3-D. TRACE 3-D is an envelope (matrix) code, which includes a linear space charge model, that was originally developed to model bunched beams in magnetic transport systems and radiofrequency (RF) accelerators. Several new optical models for a number of electrostatic lenses and accelerator columns have been developed recently that allow the code to be used for modeling beamlines and accelerators with electrostatic components. The new models include a number of options for: (1) Einzel lenses, (2) accelerator columns, (3) electrostatic prisms, and (4) electrostatic quadrupoles. A prescription for setting up the initial beam appropriate to modeling 2-D (continuous) beams has also been developed. The models for electrostatic prisms are described in this paper. The electrostatic prism model options allow the modeling of cylindrical, spherical, and toroidal electrostatic deflectors. The application of these models in the development of ion-beam transport systems is illustrated through the modeling of a spherical electrostatic analyzer as a component of the new low energy beamline at CAMS.
Date: October 21, 1999
Creator: Brown, T.A. & Gillespie, G.H.
Partner: UNT Libraries Government Documents Department

Interannual/decadal variability in MJO activity as diagnosed in the 40-year NCEP/NCAR reanalysis and simulated in an ensemble of GISST integrations

Description: The Madden-Julian Oscillation (MJO) is the dominant mode of tropical variability at intraseasonal timescales. It displays substantial interannual variability in intensity which may have important implications for the predictability of the coupled system. The reasons for this interannual variability are not understood. The interannual behaviour of the MJO has been diagnosed initially in the 40-year NCEP/NCAR Reanalysis by calculating the variance of the 20-100 day filtered zonal mean zonal wind (10 o N-10 o S averaged) in a 100- day moving window. The results suggest that prior to the mid-1970s the activity of the MJO was consistently lower than during the latter part of the record. This may be related to either inadequacies in the data coverage, particularly over the tropical Indian Ocean prior to the introduction of satellite observations, or to the real effects of a decadal timescale warming in the tropical SSTs. This interdecadal trend is captured by the dominant EOF (explaining 28% of the variance) of the monthly mean SSTs (after removal of the mean seasonal cycle), as used in the NCEP/NCAR Reanalysis for the region of the tropics where the MJO is convectively active (i.e., 60 o E-180 o E, 20 o S-20 o N). During the latter part of 1970�s there was an abrupt change from a predominantly negative PC1 (i.e. colder Indian Ocean) to a positive PC1 (i.e. warmer Indian Ocean), indicative of a general warming of the tropical Indian Ocean by at least 0.5 o K over the last 40 years. However, on interannual timescales, the teleconnection patterns between MJO activity and SST show only a weak, barely significant, influence of El Niño in which the MJO is more active during the cold phase. As well as the NCEP/NCAR Reanalysis, a 4-member ensemble of 45 year integrations with the Hadley Centre climate model ...
Date: April 21, 1999
Creator: Nortley, F; Rowell, D P; Slingo, J M & Sperber, K R
Partner: UNT Libraries Government Documents Department

Electroweak and higgs physics at D0

Description: We present recent results from the D0 experiment on W and Z boson production using {approx} 50 pb{sup -1} of Run II data recorded at the center of mass energy of 1.96 TeV at the Fermilab Tevatron. Initial studies of W/Z + 2 jets production that are relevant to Higgs searches are also discussed.
Date: January 21, 2004
Creator: Varelas, Nikos
Partner: UNT Libraries Government Documents Department

Reproducibility: A Major Source of Uncertainty in Weighing

Description: Balance confirmation tests usually include eccentricity, linearity, and repeatability. The latter is a measure of the random variability of the instrument. Further, repeatability is usually based on 10 consecutive measurements of a mass standard in a short period of time. The test results are used to verify the balance performs within manufacturer's specifications. These test results are often used in calculating an estimate of the uncertainty in measurements made with the balance. Uncertainty estimates, used to quantify the quality of measurements, must accurately estimate the magnitude of these errors. Does the repeatability test provide a realistic estimate of the random variation in the weighing process? The authors had concerns that it may not. The reproducibility estimate of the balance needs to be determined for the variables that will change between measurements of the same material while the other parameters are held constant by procedures and training.
Date: May 21, 2003
Creator: Clark, J.P.
Partner: UNT Libraries Government Documents Department

First-principles study of high explosive decomposition energetics

Description: The mechanism of the gas phase unimolecular decomposition of hexahydro-1,3,5,- trinitro- 1,3,5,-triazine (RDX) has been investigated using first principles gradient corrected density functional theory. Our results show that the dominant reaction channel is the N-NO* bond rupture, which has a barrier of 34.2 kcal/mol at the B- PW9 l/cc-pVDZ level and is 18.3 kcal/mol lower than that of the concerted ring fission to three methylenenitramine molecules. In addition, we have carried out a systematic study of homolytic bond dissociation energies of 14 other high explosives at the B-PW91/D95V level. We find that the correlation between the weakest bond strength and high explosive sensitivity is strong
Date: August 21, 1998
Creator: Wu, C J
Partner: UNT Libraries Government Documents Department

Future of B Physics at CDF and D0

Description: In this contribution to the panel discussion on ''The Future of Hadron B Experiments'' held at the 8th International Conference on B Physics at Hadron Machines (Beauty 2002) at Santiago de Compostela, Spain, June 17-21, 2002, we explore the physics potential for B physics at CDF and D0 in five years and beyond. After a brief introduction to precision flavour physics, we concentrate our discussion on the future of CP violation by evaluating the prospects for measuring the CKM angles {beta}, {gamma} and {alpha} at the Tevatron Collider experiments CDF and D0 by the end of Run II.
Date: February 21, 2003
Creator: Paulini, M.
Partner: UNT Libraries Government Documents Department


Description: A new drift detector prototype which provides suppression of the lateral diffusion of electrons has been tested as a function of the signal charge up to high charge levels, when electrostatic repulsion is not negligible. The lateral diffusion of the electron cloud has been measured for injected charges up to 2 {center_dot} 10{sup 5} electrons. The maximum number of electrons for which the suppression of the lateral spread is effective is obtained.
Date: October 21, 1995
Partner: UNT Libraries Government Documents Department

A Study of Weld Porosity in Containers for the Storage of Plutonium Containing Materials

Description: An autogenous GTAW closure weld was developed for the Department of Energy's (DOE) primary container for the storage of plutonium-bearing materials. The occurrence of porosity at the tie-in point of the closure weld was investigated. The primary cause of the porosity was linked to the geometry at the root of the closure weld joint. This paper describes the mechanistic model that was developed to describe and predict the porosity.
Date: April 21, 2003
Creator: Daugherty, W.L.
Partner: UNT Libraries Government Documents Department

Mutual passivation effects in Si-doped diluted In{sub y}Ga{sub 1-y}As{sub 1-x}N{sub x} alloys

Description: We report systematic investigations of the mutual passivation effects of Si hydrogenic donors and isovalent nitrogen in dilute InGaAs{sub 1-x}N{sub x} alloys. Upon thermal annealing at temperatures above {approx}650 C, the Si atoms diffuse assisted by the formation and migration of Ga vacancies. When they find nitrogen atoms, they form stable Si{sub Ga}-N{sub As} nearest-neighbor pairs. As a result of the pair formation, the electrical activity of Si{sub Ga} donors is passivated. At the same time, the effect of an equal number of N{sub As} atoms is also deactivated. The passivation of the shallow donors and the N{sub As} atoms is manifested in a drastic reduction in the free electron concentration and, simultaneously, an increase in the fundamental band gap. Analytical calculations of the passivation process based on Ga vacancies mediated diffusion show good agreement with the experimental results. Monte Carlo simulations have also been performed for a comparison with these results. The effects of mutual passivation on the mobility of free electrons are quantitatively explained on the basis of the band anticrossing model. Optical properties of annealed Si-doped InGaAs{sub 1-x}N{sub x} samples are also discussed.
Date: July 21, 2003
Creator: Wu, J.; Yu, K.M.; Walukiewicz, W.; He, G.; Haller, E.E.; Mars, D.E. et al.
Partner: UNT Libraries Government Documents Department

Future accelerators (?)

Description: I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.
Date: August 21, 2003
Creator: Womersley, John
Partner: UNT Libraries Government Documents Department

An Evaluation of Activated Bismuth Isotopes in Environmental Samples From the Former Western Pacific Proving Grounds

Description: {sup 207}Bi (t{sub 1/2}=32.2 y) was generated by activation of weapons material during a few ''clean'' nuclear tests at the U.S. Western Pacific Proving Grounds of Enewetak and Bikini Atolls. The radionuclides first appeared in the Enewetak environment during 1958 and in the environment of Bikini during 1956. Crater sediments from Bikini with high levels of {sup 207}Bi were analyzed by gamma spectrometry in an attempt to determine the relative concentrations of {sup 208}Bi (t{sup 1/2} = 3.68 x 10{sup 5} y). The bismuth isotopes were probably generated during the ''clean'', 9.3 Mt Poplar test held on 7/12/58. The atom ratio of {sup 208}Bi to {sup 207}Bi (R value) ranges from {approx}12 to over 200 in sections of core sediments from the largest nuclear crater at Bikini atoll. The presence of bismuth in the device is suggested to account for R values in excess of 10.
Date: March 21, 2000
Creator: Robison, W.L.; Brunk, J.A. & Jokela, T.A.
Partner: UNT Libraries Government Documents Department

PMESH: A parallel mesh generator

Description: The Parallel Mesh Generation (PMESH) Project is a joint LDRD effort by A Division and Engineering to develop a unique mesh generation system that can construct large calculational meshes (of up to 10{sup 9} elements) on massively parallel computers. Such a capability will remove a critical roadblock to unleashing the power of massively parallel processors (MPPs) for physical analysis. PMESH will support a variety of LLNL 3-D physics codes in the areas of electromagnetics, structural mechanics, thermal analysis, and hydrodynamics.
Date: October 21, 1994
Creator: Hardin, D.D.
Partner: UNT Libraries Government Documents Department

Inertial Fusion Energy Development: What is Needed and What will be Learned at the National Ignition Facility

Description: Successful development of inertial fusion energy (IFE) requires that many technical issues be resolved. Separability of drivers, targets, chambers and other IFE power plant subsystems allows resolution of many of these issues in off-line facilities and programs. Periodically, major integrated facilities give a snapshot of the rate of progress toward the ultimate solutions. The National Ignition Facility (NIF) and Laser Megajoule (LMJ) are just such integrating facilities. This paper reviews the status of IFE development and projects what will be learned from the NIF and LMJ.
Date: October 21, 1999
Creator: Hogan, W.J.
Partner: UNT Libraries Government Documents Department

Thin films and surface patterning with BEDT-TTF based charge transfer salts.

Description: Densely covered (ET)X{sub 2} thin films can be selectively electrodeposited on gold electrodes. The insulating (ET)X{sub 2} films are converted to (ET){sub 2}X conductive films through a novel conproportionation reaction. Both ET and ET salt patterns can be prepared with the PDMS stamping technique with use of an ET derivative with a dodecanethiol chain for surface derivatization. These solution procedures open up the possibility to prepare conductive and superconductive charge-transfer salt thin films as well as patterns.
Date: August 21, 2002
Creator: Wang, H. H.; Han, C. Y.; Noh, D.-Y.; Shin, K.-S.; Willing, G. A. & Geiser, U.
Partner: UNT Libraries Government Documents Department

Near-Term Demonstration of Benign, Sustainable, Nuclear Power

Description: Nuclear power reactors have been studied, researched, developed, constructed, demonstrated, deployed, operated, reviewed, discussed, praised and maligned in the United States for over half a century. These activities now transcend our national borders and nuclear power reactors are in commercial use by many nations. Throughout the world, many have been built, some have been shut down, and new ones are coming on line. Almost one-fifth of the world's electricity in 1997 was produced from these reactors. Nuclear power is no longer an unknown new technology. A large increase in world electricity demand is projected for the coming century. In lieu of endless research programs on ''new'' concepts, it is now time to proceed vigorously with widespread deployment of the best nuclear power option for which most parameters are already established. Here, we develop an aggressive approach for initiating the deployment of such a system--with the potential to produce over half of the world's electricity by mid-century, and to continue at that level for several centuries.
Date: September 21, 2000
Creator: Walter, C.E.
Partner: UNT Libraries Government Documents Department

Methodology for Estimating Ingestion Dose for Emergency Response at SRS

Description: At the Savannah River Site (SRS), emergency response computer models are used to estimate dose following releases of radioactive materials to the environment. Downwind air and ground concentrations and their associated doses from inhalation and ground shine pathways are estimated. The emergency response model (PUFF-PLUME) uses real-time data to track either instantaneous (puff) or continuous (plume) releases. A site-specific ingestion dose model was developed for use with PUFF-PLUME that includes the following ingestion dose pathways pertinent to the surrounding SRS area: milk, beef, water, and fish. The model is simplistic and can be used with existing code output.
Date: July 21, 2003
Creator: Simpkins, A.A.
Partner: UNT Libraries Government Documents Department

Ceramic waste form production and development at ANL-West.

Description: Argonne National Laboratory has developed a method to stabilize spent electrolyte salt discarded from electrorefiners (ER) used to treat spent nuclear fuel. The salt is stabilized in a ceramic using a pressureless consolidation technique. The starting material is zeolite 4A which is used as the host for the fission product and actinide rich salt. Glass frit is added to the salt loaded zeolite before processing to act as a binder. The zeolite 4A is converted to sodalite during processing via pressureless consolidation. This process differs from one used in the past that employed a hot isostatic press. Ceramic is created at 925 C and atmospheric pressure instead of the high pressures used in hot isostatic pressing. Process flow sheets, off-gas test results, processing equipment, and leech test results are presented.
Date: August 21, 2002
Creator: Battisti, T. J.; Goff, K. M.; Bateman, K. J.; Simpson, M. F. & Lind, J. P.
Partner: UNT Libraries Government Documents Department