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Benchmark field study of deep neutron penetration (open access)

Benchmark field study of deep neutron penetration

A unique benchmark neutron field has been established at the Lawrence Livermore National Laboratory (LLNL) to study deep penetration neutron transport. At LLNL, a tandem accelerator is used to generate a monoenergetic neutron source that permits investigation of deep neutron penetration under conditions that are virtually ideal to model, namely the transport of mono-energetic neutrons through a single material in a simple geometry. General features of the Lawrence Tandem (LATAN) benchmark field are described with emphasis on neutron source characteristics and room return background. The single material chosen for the first benchmark, LATAN-1, is a steel representative of Light Water Reactor (LWR) Pressure Vessels (PV). Also included is a brief description of the Little Boy replica, a critical reactor assembly designed to mimic the radiation doses from the atomic bomb dropped on Hiroshima, and its us in neutron spectrometry. 18 refs.
Date: June 10, 1991
Creator: Morgan, J. F.; Sale, K. (Lawrence Livermore National Lab., CA (USA) ); Gold, R.; Roberts, J. H. & Preston, C. C. (Metrology Control Corp., Richland, WA (USA) )
System: The UNT Digital Library
Electron energies in metals (open access)

Electron energies in metals

The modern era of electron-electron interactions began a decade ago. Plummer's group initiated a program of using angular resolved photoemission to examine the band structure of the simple metals. Beginning with aluminum, and carrying on to sodium and potassium, they always found that the occupied energy bands were much narrower than expected. For example, the compressed energy bands for metallic potassium suggest a band effective mass of m* = 1.33m{sub e}. This should be compared to the band mass found from optical conductivity m*/m{sub e} = 1.01 {plus minus} 0.01. The discrepancy between these results is startling. It was this great difference which started my group doing calculations. Our program was two-fold. On one hand, we reanalyzed the experimental data, in order to see if Plummer's result was an experimental artifact. On the other hand, we completely redid the electron-electron self-energy calculations for simple metals, using the most modern choices of local-field corrections and vertex corrections. Our results will be reported in these lectures. They can be summarized as following: Our calculations give the same effective masses as the older calculations, so the theory is relatively unchanged; Our analysis of the experiments suggests that the recent measurements of band narrowing …
Date: July 10, 1991
Creator: Mahan, G.D. (Oak Ridge National Lab., TN (United States) Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy)
System: The UNT Digital Library
Chasing the x sub f dependence of J/. Psi. production (open access)

Chasing the x sub f dependence of J/. Psi. production

We discuss the combined effects of hard scattering processes and intrinsic heavy-quark components in the hadron wavefunction on the x{sub f} dependence of J/{psi} production. The A dependence arises from nuclear absorption, comover interactions, shadowing of parton distributions, and intrinsic heavy quarks. 9 refs., 1 fig.
Date: June 10, 1991
Creator: Vogt, R.
System: The UNT Digital Library
The future of defense and technology (open access)

The future of defense and technology

This document provides an insight into the future of national defense and the impacts of utilizing technology for improved defensive postures. (FI)
Date: January 10, 1991
Creator: Teller, E.
System: The UNT Digital Library
Pion interferometry and resonances in pp and AA collisions (open access)

Pion interferometry and resonances in pp and AA collisions

We study the sensitivity of pion interferometry in {bar p}p and {bar p}p collisions at ISR energies to the resonance abundance. We show that those data are not compatible with the full resonance fractions predicted by the Lund model. The preliminary S+S and O+Au data at 200 GeV are, however, not incompatible with the Lund predictions, although their sensitivity to resonances is significantly weaker than in the pp/{bar p}p case.
Date: December 10, 1991
Creator: Padula, S.S. (Universidade Estadual Paulista, Sao Paulo, SP (Brazil). Inst. de Fisica Teorica) & Gyulassy, M. (Lawrence Berkeley Lab., CA (United States))
System: The UNT Digital Library
Analysis of electron heat transport in femtosecond laser-plasma interactions with layered solid targets and with thin foils (open access)

Analysis of electron heat transport in femtosecond laser-plasma interactions with layered solid targets and with thin foils

We analyze two types of experiments that enhance our knowledge of the electron heat transport in femtosecond laser produced plasmas. The first involves layered targets and the fall off of substrate signal with increasing overlayer thickness. The experiment uncertainties are too large at present to definitively quantify the heat transport. The second involves the radiative output from thin foils. The behavior of the spectral response to foil thickness implies that our understanding of the transport within the foils is quite good. 12 refs., 11 figs.
Date: January 10, 1991
Creator: Rosen, Mordecai D.
System: The UNT Digital Library
SANDROS: A motion planner with performance proportional to task difficulty (open access)

SANDROS: A motion planner with performance proportional to task difficulty

To address the need of a practical motion planner for manipulators, we present an efficient and resolution-complete algorithm that has performance commensurate with task difficulty. The algorithm uses SANDROS, a new search strategy that combines hierarchical, nonuniform-multi-resolution, and best-fit search to find a near-optimal solution in the configuration space. This algorithm can be applied to any manipulator, and has been tested with 5 and 6-degree-of-freedom robots, with execution time ranging from 20 seconds to 10 minutes on a 16 MIPS workstation. 14 refs., 3 figs., 1 tab.
Date: September 10, 1991
Creator: Chen, Pang C. & Hwang, Yong K.
System: The UNT Digital Library
Programming a real code in a functional language (part 1) (open access)

Programming a real code in a functional language (part 1)

For some, functional languages hold the promise of allowing ease of programming massively parallel computers that imperative languages such as Fortran and C do not offer. At LLNL, we have initiated a project to write the physics of a major production code in Sisal, a functional language developed at LLNL in collaboration with researchers throughout the world. We are investigating the expressibility of Sisal, as well as its performance on a shared-memory multiprocessor, the Y-MP. An interesting aspect of the project is that Sisal modules can call Fortran modules, and are callable by them. This eliminates the rewriting of 80% of the production code that would not benefit from parallel execution. Preliminary results indicate that the restrictive nature of the language does not cause problems in expressing the algorithms we have chosen. Some interesting aspects of programming in a mixed functional-imperative environment have surfaced, but can be managed. 8 refs.
Date: September 10, 1991
Creator: Hendrickson, C.P.
System: The UNT Digital Library
Pion interferometry and resonances in pp and AA collisions (open access)

Pion interferometry and resonances in pp and AA collisions

We study the sensitivity of pion interferometry in {bar p}p and {bar p}p collisions at ISR energies to the resonance abundance. We show that those data are not compatible with the full resonance fractions predicted by the Lund model. The preliminary S+S and O+Au data at 200 GeV are, however, not incompatible with the Lund predictions, although their sensitivity to resonances is significantly weaker than in the pp/{bar p}p case.
Date: December 10, 1991
Creator: Padula, S. S. & Gyulassy, M.
System: The UNT Digital Library
Estimating market penetration of new district heating and cooling systems using a combination of economic cost and diffusion models (open access)

Estimating market penetration of new district heating and cooling systems using a combination of economic cost and diffusion models

The economic-cost model and the diffusion model are among the many market-penetration forecasting approaches that are available. These approaches have been used separately in many applications. In this paper, the authors briefly review these two approaches and then describe a methodology for forecasting market penetration using both approaches sequentially. This methodology is illustrated with the example of market-penetration forecasting of new district heating and cooling (DHC) systems in the Argonne DHC Market Penetration Model, which was developed and used over the period 1979--1983. This paper discusses how this combination approach, which incorporates the strengths of the economic-cost and diffusion models, has been superior to any one approach for market forecasts of DHC systems. Also discussed are the required modifications for revising and updating the model in order to generate new market-penetration forecasts for DHC systems. These modifications are required as a result of changes in DHC engineering, economic, and market data from 1983 to 1990. 13 refs., 5 figs., 2 tabs.
Date: May 10, 1991
Creator: Teotia, Arvind P. S. & Karvelas, Dimitrios E.
System: The UNT Digital Library