Two-axis Beam Steering Mirror Control system for Precision Pointing and Tracking Applications (open access)

Two-axis Beam Steering Mirror Control system for Precision Pointing and Tracking Applications

Precision pointing and tracking of laser beams is critical in numerous military and industrial applications. This is particularly true for systems requiring atmospheric beam propagation. Such systems are plagued by environmental influences which cause the optical signal to break up and wander. Example applications include laser communications, precision targeting, active imaging, chemical remote sensing, and laser vibrometry. The goal of this project is to build a beam steering system using a two-axis mirror to maintain precise pointing control. Ultimately, position control to 0.08% accuracy (40 {micro}rad) with a bandwidth of 200 Hz is desired. The work described encompasses evaluation of the instrumentation system and the subsequent design and implementation of an analog electronic controller for a two-axis mirror used to steer the beam. The controller operates over a wide temperature range, through multiple mirror resonances, and is independent of specific mirrors. The design was built and successfully fielded in a Lawrence Livermore National Laboratory free-space optics experiment. All measurements and performance parameters are derived from measurements made on actual hardware that was built and field tested. In some cases, specific design details have been omitted that involve proprietary information pertaining to Lawrence Livermore National Laboratory patent positions and claims. These …
Date: February 8, 2006
Creator: Ulander, K
System: The UNT Digital Library
Exploration of deeply virtual Compton scattering on the neutron in the Hall A of Jefferson Laboratory (open access)

Exploration of deeply virtual Compton scattering on the neutron in the Hall A of Jefferson Laboratory

Generalized Parton Distributions (GPDs) are universal functions which provide a comprehensive description of hadron properties in terms of quarks and gluons. Deeply Virtual Compton Scattering (DVCS) is the simplest hard exclusive process involving GPDs. In particular, the DVCS on the neutron is mostly sensitive to E, the less constrained GPD, wich allows to access to the quark angular momentum. The first dedicated DVCS experiment on the neutron ran in the Hall A of Jefferson Lab in fall 2004. The high luminosity of the experiment and the resulting background rate recquired specific devices which are decribed in this document. The analysis methods and the experiment results, leading to preliminary constraints on the GPD E, are presented.
Date: December 8, 2006
Creator: Mazouz, Malek
System: The UNT Digital Library
A Parallel Ocean Model With Adaptive Mesh Refinement Capability For Global Ocean Prediction (open access)

A Parallel Ocean Model With Adaptive Mesh Refinement Capability For Global Ocean Prediction

An ocean model with adaptive mesh refinement (AMR) capability is presented for simulating ocean circulation on decade time scales. The model closely resembles the LLNL ocean general circulation model with some components incorporated from other well known ocean models when appropriate. Spatial components are discretized using finite differences on a staggered grid where tracer and pressure variables are defined at cell centers and velocities at cell vertices (B-grid). Horizontal motion is modeled explicitly with leapfrog and Euler forward-backward time integration, and vertical motion is modeled semi-implicitly. New AMR strategies are presented for horizontal refinement on a B-grid, leapfrog time integration, and time integration of coupled systems with unequal time steps. These AMR capabilities are added to the LLNL software package SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) and validated with standard benchmark tests. The ocean model is built on top of the amended SAMRAI library. The resulting model has the capability to dynamically increase resolution in localized areas of the domain. Limited basin tests are conducted using various refinement criteria and produce convergence trends in the model solution as refinement is increased. Carbon sequestration simulations are performed on decade time scales in domains the size of the North Atlantic and …
Date: September 8, 2005
Creator: Herrnstein, A
System: The UNT Digital Library
Ligand Rearrangements of Organometallic Complexes inSolution (open access)

Ligand Rearrangements of Organometallic Complexes inSolution

Many chemical reactions utilize organometallic complexes as catalysts. These complexes find use in reactions as varied as bond activation, polymerization, and isomerization. This thesis outlines the construction of a new ultrafast laser system with an emphasis on the generation of tunable mid-infrared pulses, data collection, and data analysis.
Date: May 8, 2006
Creator: Shanoski, Jennifer E.
System: The UNT Digital Library
NIF facts (open access)

NIF facts

The National Ignition Facility (NIF) will use the world's largest laser to compress and heat BB-sized capsules of fusion fuel to thermo-nuclear ignition. NIF experiments will produce temperatures and densities like those in the Sun or in an exploding nuclear weapon. The experiments will help scientists sustain confidence in the nuclear weapon stockpile without nuclear tests as a unique element of the DOE'S Stockpile Stewardship Program and will produce additional benefits in basic science and fusion energy.
Date: September 8, 2000
Creator: Carpenter, J & Warner, B
System: The UNT Digital Library
Software Vulnerability Taxonomy Consolidation (open access)

Software Vulnerability Taxonomy Consolidation

In today's environment, computers and networks are increasing exposed to a number of software vulnerabilities. Information about these vulnerabilities is collected and disseminated via various large publicly available databases such as BugTraq, OSVDB and ICAT. Each of these databases, individually, do not cover all aspects of a vulnerability and lack a standard format among them, making it difficult for end-users to easily compare various vulnerabilities. A central database of vulnerabilities has not been available until today for a number of reasons, such as the non-uniform methods by which current vulnerability database providers receive information, disagreement over which features of a particular vulnerability are important and how best to present them, and the non-utility of the information presented in many databases. The goal of this software vulnerability taxonomy consolidation project is to address the need for a universally accepted vulnerability taxonomy that classifies vulnerabilities in an unambiguous manner. A consolidated vulnerability database (CVDB) was implemented that coalesces and organizes vulnerability data from disparate data sources. Based on the work done in this paper, there is strong evidence that a consolidated taxonomy encompassing and organizing all relevant data can be achieved. However, three primary obstacles remain: lack of referencing a common ''primary …
Date: December 8, 2004
Creator: Polepeddi, S
System: The UNT Digital Library