This paper describes the design, development and performance of a lightweight precision gimbal with dual-axis slew capability to be used in a closed-loop optical tracking system at Lawrence Livermore National Laboratory-LLNL. The motivation for the development of this gimbal originates from the need to acquire and accurately localize warm objects (T{approximately}500 K) in a cluttered background. The design of the gimbal is centered around meeting the following performance requirements: pointing accuracy with control < 35 {mu}rad-(1-{omega}); slew capability > 0.2 rad/sec; mechanical weight < 5 kg. These performance requirements are derived by attempting to track a single target from multiple satellites in low Earth orbit using a mid-wave infrared camera. Key components in the gimbal hardware that are essential to meeting the performance objectives include a nickel plated beryllium mirro, an accurate lightweight capacitive pickoff device for angular measurement about the elevation axis, a 16-bit coarse/fine resolver for angular measurement about the azimuth axis, a toroidally wound motor with low hysteresis for providing torque about the azimuth axis, and the selection of beryllium parts to insure high stiffness to weight ratios and more efficient thermal conductivity. Each of these elements are discussed in detail to illustrate the design trades performed …

This Paper develops a statistical strength theory for three-dimensionally (3-D) oriented short-fiber reinforced composites. Short-fiber composites are usually reinforced with glass and ceramic short fibers and whiskers. These reinforcements are brittle and display a range of strength values, which can be statistically characterized by a Weibull distribution. This statistical nature of fiber strength needs to be taken into account in the prediction of composite strength. In this paper, the statistical nature of fiber strength is incorporated into the calculation of direct fiber strengthening, and a maximum-load composite failure criterion is adopted to calculate the composite strength. Other strengthening mechanisms such as residual thermal stress, matrix work hardening, and short-fiber dispersion hardening are also briefly discussed.

As Lawrence Livermore National Laboratory moves forward with the design of the National Ignition Facility (NIF) in the Inertial Confinement Fusion (ICF) program, issues relating to the detection and measurement of laser-induced damage on large optics must be addressed. Currently, microscopy is used to evaluate surface quality and measure damage thresholds on small witness samples. In order to evaluate large areas, an automated system was constructed which can scan optics with dimensions as large as 1 meter and weighing as much as 400 pounds. The use of microscopy as the main test diagnostic has been replaced with an optical scatter detection system. Now large areas can be rastered, and maps can be generated, reflecting inherent and laser-induced scatter in multilayer optical coatings and bulk materials. The integrated scattered light from a test piece is measured in transmission using a HeNe laser as the probe source. When the probe beam is overlapped on a pulsed, high power, ND:YAG laser beam, damage related scatter may be measured. This technique has been used for: (1) mapping of inherent scatter in an optic, (2) on-the-fly damage detection during a high fluence raster scan of an optic, and (3) single site damage evaluation for the …

This article describes the measurement of collision-induced interaction cross sections for 1-7 MeV diatomic boron molecular ions incident on a nitrogen gas target by using a differentially pumped gas cell.

Radioactive nuclear beams are rapidly coming to the fore as an important alternative to traditional measurements in nuclear astrophysics. Radioactive nuclei are scattered off the strong electromagnetic fields of a heavy ion, such as lead, providing an independent measurement of electromagnetic cross sections that are difficult to measure otherwise. In this paper, we examine the corrections to the semi-classical ``equivalent photon spectrum`` used to analyze these experiments, and derive an improved spectrum, valid in the long wavelength limit, that includes the effects of the size of the heavy ion, the non-zero longitudinal momentum transfer required by kinematics, and the response of the target nucleus to be off-shell photon.

Dual-band infrared (DBIR) thermal imaging is a promising, non-contact, nondestructive evaluation tool to evaluate the amount of deteriorated concrete on asphalt-covered bridge decks. We conducted proof-of-principle demonstrations to characterize defects in concrete structures which could be detected with DBIR thermal imaging. We constructed two identical concrete slabs with synthetic delaminations, e.g., 1/8-in. thick styrofoam squares, implanted just above the 2-in.-deep steel reinforcement bars. We covered one of the slabs with a 2-in. layer of asphalt. We mounted the DBIR cameras on a tower platform, to simulate the optics needed to conduct bridge-deck inspections from a moving vehicle. We detected 4-in. implants embedded in concrete and 9-in. implants embedded in asphalt-covered concrete. The midday (above-ambient) and predawn (below-ambient) delamination-site temperatures correlated with the implant sizes. Using DBIR image ratios, we enhanced thermal-contrast and removed emissivity-noise, e.g., from concrete compositional variations and clutter. Using the LLNL/VIEW code, we removed the asphalt thermal-gradient mask, to depict the 4-in. deep, 9-in. square, concrete implant size. We plan to image bridge deck defects, from a moving vehicle, for accurate estimations of the amount of deteriorated concrete impairing the deck integrity. Potential longterm benefits are affordable and reliable rehabilitation for asphalt-covered decks.

There has been some interest lately in the need for ``authenticated signalling``, and the development of signalling specifications by the ATM Forum that support this need. The purpose of this contribution is to show that if authenticated signalling is required, then supporting signalling facilities for directory services (i.e. key management) are also required. Furthermore, this contribution identifies other security related mechanisms that may also benefit from ATM-level signalling accommodations. For each of these mechanisms outlined here, an overview of the signalling issues and a rough cut at the required fields for supporting Information Elements are provided. Finally, since each of these security mechanisms are specified by a number of different standards, issues pertaining to the selection of a particular security mechanism at connection setup time (i.e. specification of a required ``Security Quality of Service``) are also discussed.

The Department of Energy must demonstrate the effectiveness of the Waste Isolation Pilot Plant (WIPP) as a permanent repository for the disposal of transuranic (TRU) waste. Performance assessments of the WIPP require that estimates of the transportability and outcome of the radionuclides (actinides) be determined from disposal rooms that may become either partially or completely filled with brine. Federal regulations limit the amount of radioactivity that may be unintentionally released to the accessible environment by any mechanism during the post closure phase up to 10,000 years. Thermodynamic models have been developed to predict the concentrations of actinides in the WIPP disposal rooms under various situations and chemical conditions. These models are based on empirical and theoretical projections of the chemistry that might be present in and around the disposal room zone for both near and long-term periods. The actinides that are known to be present in the TRU wastes (and are included in the model) are Th, U, Np, Pu, and Am. Knowledge of the chemistry that might occur in the disposal rooms when the waste comes in contact with brine is important in understanding the range of oxidation states that might be present under different conditions. There is a …

Two chronosequence of unsaturated buried loess sediments ranging in age from &lt;10,000 years to &gt;1 million years were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession were inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Samples were collected by coring at two sites 40 km apart in the Palouse region of eastern Washington State near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the elevation of the Winona site is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was {approx}250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: {approx}1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments …

The Waste Isolation Pilot Plant (WIPP) project was undertaken in response to the growing need for a national repository for transuranic (TRU) waste. Guidelines for WIPP specify that any waste item to be interred must be fully characterized and analyzed to determine the presence of chemical compounds designated hazardous and certain toxic elements. The Transuranic Waste Characterization Program (TWCP) was launched to develop analysis and quality guidelines, certify laboratories, and to oversee the actual waste characterizations at the laboratories. ORNL is participating in the waste characterization phase and brings to bear a variety of analytical techniques including ICP-AES, cold vapor atomic absorption, and instrumental neutron activation analysis (INAA) to collective determine arsenic, cadmium, barium, chromium, mercury, selenium, silver, and other elements. All of the analytical techniques involved participate in a cooperative effort to meet the project objectives. One important component of any good quality assurance program is determining when an alternate method is more suitable for a given analytical problem. By bringing to bear a whole arsenal of analytical techniques working toward common objectives, few analytical problems prove to be insurmountable. INAA and ICP-AES form a powerful pair when functioning in this cooperative manner. This paper will provide details of …

A series of hafnia/silica, oblique incidence (56{degrees}), 1064 nm high reflectors (HRs) were prepared and coated with silica overlayers of varying optical thickness from {lambda}/2 to 4{lambda} in order to determine the effect of an overlayer on the laser-damage resistance of the HRs. The stress and laser damage thresholds for S and P polarization of the HRs were measured, and the damage sites for P polarization examined by Atomic Force Microscopy (AFM). All the multilayers were found to be in compression, with an intrinsic stress increasing with overlayer thickness. The presence of an overlayer and its thickness did not affect the damage threshold significantly. However, the presence of an overlayer greatly influenced the size and morphology of the damage. First, the overlayer prevented catastrophic ``burns`` of the hafnia top layer. Second, as the overlayer thickness increased, two distinct damage morphologies were found: agged pits and round craters. The diameter of these pits and craters then increased somewhat with thicker overlayers. The depths of the pits and craters also increased with overlayer thickness, and the depths showed failure occurring at the interfaces below the hafnia layers. The side-wall angles of the craters were shallower with thicker overlayers, but there was no …

Researchers at the Lawrence Livermore National Laboratory and EG&G Energy Measurements are developing a new solid-state power system for two proposed accelerators. One of the accelerators is a circular arrangement of induction cells called a recirculator. It is designed to accelerate heavy ions for an inertial fusion study that proposes to substitute heavy-ion beams for laser beams as the driver for fusion targets. The other accelerator is a linear induction accelerator for electron beams called the Advanced Radiographic Machine (ARM). Both accelerators require their induction cells to be pulsed at a very high repetition frequency (prf) for a short burst containing 5 to 15 pulses. The recirculator has a pulse schedule that varies in pulse width from 1 {mu}s to 400 ns and in prf from 50 to 150 kHz. The ARM accelerator has a pulse schedule that varies in pulse width from 1 {mu}s to 200 ns and in prf from 150 kHz to 1 MHz. The need for complex pulse agility in these accelerators led the authors to examine solid-state switching components that have an on/off capability. The intrinsic speed of solid-state switching satisfies the high prf requirements, while the on/off switching action of some semiconductor devices enables …

In early 1991, the Security Council of the United Nations tasked the Director General of the International Atomic Energy Agency, with the assistance and cooperation of the United Nations Special Commission, to oversee the destruction, removal or rendering harmless of nuclear weapons material and capabilities in Iraq. The conduct of the nuclear inspections, and the subsequent activities (identification, destruction, removal rendering harmless), have provided a wealth of experience and insight into the inspection and monitoring process as well as into the political realities of such an operation. The early inspections were conducted in an atmosphere of discovery and inexperience on both the part of the Iraqis and the IAEA and UNSCOM. As time went on, the Iraqis became more adept at hiding and obscuring relevant documents and equipment, and the inspection teams became more knowledgeable about inspection and investigative techniques, and the pre-existing Iraqi programs. A continuous monitoring presence in Iraq has now been established and an import/export monitoring regime is being developed. While steps taken to date have proven effective in inhibiting resumption of nuclear weaponization activities, it remains to be seen how effective these measures will be in the future. The external and internal conditions which led the …