ECLOUD in PS2, PS+, SPS+: AN UPDATE (open access)

ECLOUD in PS2, PS+, SPS+: AN UPDATE

We present an update of our results for the electron-cloud build-up for several upgrades proposed for the LHC injectors. Specifically, we have re-examined our published results for the ecloud heat load [1] from the perspective of numerical convergence of the simulations vis-a-vis the integration time step {Delta}t. We repeated most of the simulations with ever smaller values of {Delta}t until we reached stable results, indicating numerical convergence; this was achieved at 200-500 slices per bunch, depending on the particular case. In all cases examined, the simulated heat load decreases monotonically, until the limit is reached, as {Delta}t decreases in the range explored, hence the stable results are more favorable vis-a-vis the heat load than the previous ones. This is particularly true for a bunch spacing t{sub b} = 25 ns.
Date: May 22, 2007
Creator: Furman, M. A.
Object Type: Article
System: The UNT Digital Library
Ab Initio Study of 40Ca with an Importance Truncated No-Core Shell Model (open access)

Ab Initio Study of 40Ca with an Importance Truncated No-Core Shell Model

We propose an importance truncation scheme for the no-core shell model, which enables converged calculations for nuclei well beyond the p-shell. It is based on an a priori measure for the importance of individual basis states constructed by means of many-body perturbation theory. Only the physically relevant states of the no-core model space are considered, which leads to a dramatic reduction of the basis dimension. We analyze the validity and efficiency of this truncation scheme using different realistic nucleon-nucleon interactions and compare to conventional no-core shell model calculations for {sup 4}He and {sup 16}O. Then, we present the first converged calculations for the ground state of {sup 40}Ca within no-core model spaces including up to 16{h_bar}{Omega}-excitations using realistic low-momentum interactions. The scheme is universal and can be easily applied to other quantum many-body problems.
Date: May 22, 2007
Creator: Roth, R & Navratil, P
Object Type: Article
System: The UNT Digital Library
Particle Simulation of Coulomb Collisions: Comparing the Methods of Takizuka & Abe and Nanbu (open access)

Particle Simulation of Coulomb Collisions: Comparing the Methods of Takizuka & Abe and Nanbu

The interactions of charged particles in a plasma are in a plasma is governed by the long-range Coulomb collision. We compare two widely used Monte Carlo models for Coulomb collisions. One was developed by Takizuka and Abe in 1977, the other was developed by Nanbu in 1997. We perform deterministic and stochastic error analysis with respect to particle number and time step. The two models produce similar stochastic errors, but Nanbu's model gives smaller time step errors. Error comparisons between these two methods are presented.
Date: May 22, 2007
Creator: Wang, C.; Lin, T.; Caflisch, R.; Cohen, B. & Dimits, A.
Object Type: Article
System: The UNT Digital Library
Global Cooling: Effect of Urban Albedo on Global Temperature (open access)

Global Cooling: Effect of Urban Albedo on Global Temperature

In many urban areas, pavements and roofs constitute over 60% of urban surfaces (roof 20-25%, pavements about 40%). The roof and the pavement albedo can be increased by about 0.25 and 0.10, respectively, resulting in a net albedo increase for urban areas of about 0.1. Many studies have demonstrated building cooling-energy savings in excess of 20% upon raising roof reflectivity from an existing 10-20% to about 60%. We estimate U.S. potential savings in excess of $1 billion (B) per year in net annual energy bills. Increasing albedo of urban surfaces can reduce the summertime urban temperature and improve the urban air quality. Increasing the urban albedo has the added benefit of reflecting more of the incoming global solar radiation and countering the effect of global warming. We estimate that increasing albedo of urban areas by 0.1 results in an increase of 3 x 10{sup -4} in Earth albedo. Using a simple global model, the change in air temperature in lowest 1.8 km of the atmosphere is estimated at 0.01K. Modelers predict a warming of about 3K in the next 60 years (0.05K/year). Change of 0.1 in urban albedo will result in 0.01K global cooling, a delay of {approx}0.2 years in …
Date: May 22, 2007
Creator: Akbari, Hashem; Menon, Surabi & Rosenfeld, Arthur
Object Type: Article
System: The UNT Digital Library
Charm Spectroscopy, Charm Decays And New States at BaBar (open access)

Charm Spectroscopy, Charm Decays And New States at BaBar

This document presents the recent studies of Charmed hadrons at BABAR BELLE and CLEO. Here the author focuses on the recent developments on the study of D*{sub sJ}, observation of D{sup +} {yields} K{sup +} {pi}{sup 0}, D{sup 0} - {bar D}{sup 0} mixing in the doubly cabibbo-suppressed decays using D{sup 0} {yields} K{sup +}{pi}{sup +}{pi}{sup 0} and the measurement of the decay constants using the leptonic D decays.
Date: May 22, 2007
Creator: Saleem, M. & U., /Brunel
Object Type: Article
System: The UNT Digital Library
SCOPING SUMMARY FOR THE P-AREA OPERABLE UNIT (open access)

SCOPING SUMMARY FOR THE P-AREA OPERABLE UNIT

This scoping summary supports development of the combined Remedial Investigation (RI)/Baseline Risk Assessment (BRA)/Feasibility Study (FS) for the P-Area Operable Unit (PAOU), or Combined document, which will be submitted on or before 09/28/2007. The objective of this Feasibility Study scoping summary meeting is to agree on the likely response actions to be evaluated and developed as alternatives in the combined document and agree on the uncertainties identified and whether they have been adequately managed.
Date: May 22, 2007
Creator: Kupar, J; Sadika Baladi, S & Mark Amidon, M
Object Type: Report
System: The UNT Digital Library
DECOMMISSIONING OF THE 247-F FUEL MANUFACTURING FACILITY AT THE SAVANNAH RIVER SITE (open access)

DECOMMISSIONING OF THE 247-F FUEL MANUFACTURING FACILITY AT THE SAVANNAH RIVER SITE

Building 247-F at SRS was a roughly 110,000 ft{sup 2} two-story facility designed and constructed during the height of the cold war naval buildup to provide additional naval nuclear fuel manufacturing capacity in early 1980s. The building layout is shown in Fig. 1. A photograph of the facility is shown in Fig. 2. The manufacturing process employed a wide variety of acids, bases, and other hazardous materials. As the cold war wound down, the need for naval fuel declined. Consequently, the facility was shut down and underwent initial deactivation. All process systems were flushed with water and drained using the existing process drain valves. However, since these drains were not always installed at the lowest point in piping and equipment systems, a significant volume of liquid remained after initial deactivation was completed in 1990. At that time, a non-destructive assay of the process area identified approximately 17 (+/- 100%) kg of uranium held up in equipment and piping.
Date: May 22, 2007
Creator: Santos, J & Stephen Chostner, S
Object Type: Article
System: The UNT Digital Library