We show experimentally that for a staggered scheme on a variable grid the numerical solution of the wave equation exhibits scattering of waves even when the grid varies slowly and the waves are smooth. We also show that this scattering is predicted very well by a modified equation, which thus serves as a backward error analysis.

In earlier work a model of fluorescent and Raman scattering by active molecules represented as classical electric dipoles embedded in small particles was developed. The intensity and angular distribution of the inelastically scattered radiation was shown to depend on the geometric and optical properties of the particle. The model was originally developed for particles having spherical shape and later extended to concentric spheres, cylinders, and prolate spheroids. The active molecules were originally assumed to be isotropically polarizable. The model has been recently extended to certain types of anisotropically polarizable molecules. The model had also been applied to particles having internal structure.

A simple K-band microwave interferometer has been developed at the Los Alamos National Laboratory to measure various transient properties in both energetic (high explosive) and passive (grout and Teflon) materials. The interferometer measures the position as a function of time of either a dielectric discontinuity, i.e., a shock front, or the position as a function of time of a conducting surface such as the detonation wave in a high explosive. By embedding a reflector in a dielectric material, both the particle velocity and the shock velocity may be measured at the same time and in the same place. The interferometer is constructed (with slight modifications) of commercially available microwave components. The total material cost for a complete working instrument is a few hundred dollars. Details of the construction will be given. As an example of the range of uses of the interferometer, it has been used to measure the detonation-to-deflagration transition in HMX and the shock properties of the grout in a nuclear test in Nevada. Data on these and other experiments are presented.

A two-dimensional numerical model of a high-gain (electron-beam power > input laser beam power) free-electron laser (FEL) has been constructed which includes the effects of diffraction, refraction, and off-axis electron-beam current density and wiggler field variations. In this model, laser beam propagation is governed by a paraxial wave equation with FEL source terms. Conventional resonant electron analysis is used to represent the trapping and deceleration of electrons by the electromagnetic field. The trapped electron-beam current density is forced to decrease as the size of the trapping potential decreases so that detrapping can be simulated. The variable-parameter wiggler field is chosen so that synchronism can be maintained at a single, arbitrary radial position. The magnetic field varies at other radial positions in accordance with Maxwell's equations.

This paper has brought out the unique properties of tuffs and related them to needs associated with their use as a host rock for a high level nuclear waste repository. Major issues of temperature, pore water, joints, and depositional patterns have been identified and related responses and impacts outlined in Table 1. Planned experiments have been outlined and their relationships to the rock mechanics issues summarized in Table 2. The conclusions from this paper are: (1) tuff is a complex rock and basic phenomenological understanding is incomplete; and (2) available field test facilities will be used for a series of experiments designed to improve phenomenological understanding and support repository design efforts.

A carbon steel storage canister has been designed for the dry encapsulation of spent nuclear fuel assemblies or of logs of vitrified high level radioactive waste. The canister design is in conformance with the requirements of the ASME Code, Section III, Division 1 for a Class 3 vessel. The canisters will be loaded and sealed as part of a completely remote process sequence to be performed in the hot bay of an experimental encapsulation facility at the Nevada Test Site. The final closure to be made is a full penetration butt weld between the canister body, a 12.75-in O.D. x 0.25-in wall pipe, and a mating semiellipsoidal closure lid. Due to a combination of design, application and facility constraints, the closure weld must be made in the 2G position (canister vertical). The plasma arc welding system is described, and the final welding procedure is described and discussed in detail. Several aspects and results of the procedure development activity, which are of both specific and general interest, are highlighted; these include: The critical welding torch features which must be exactly controlled to permit reproducible energy input to, and gas stream interaction with, the weld puddle. A comparison of results using automatic …