The goal of this work is to determine the feasibility of extracting the size of particles ejected from shocked metal surfaces (ejecta) from the angular distribution of light scattered by a cloud of such particles. The basis of the technique is the Mie theory of scattering, and implicit in this approach are the assumptions that the scattering particles are spherical and that single scattering conditions prevail. The meaning of this latter assumption, as far as experimental conditions are concerned, will become clear later. The solution to Maxwell’s equations for spherical particles illuminated by a plane electromagnetic wave was derived by Gustav Mie more than 100 years ago, but several modern treatises discuss this solution in great detail. The solution is a complicated series expansion of the scattered electric field, as well as the field within the particle, from which the total scattering and absorption cross sections as well as the angular distribution of scattered intensity can be calculated numerically. The detailed nature of the scattering is determined by the complex index of refraction of the particle material as well as the particle size parameter, x, which is the product of the wavenumber of the incident light and the particle radius, i.e. x = 2rπ= λ. Figure 1 shows the angular distribution of scattered light for different particle size parameters and two orthogonal incident light polarizations as calculated using the Mie solution. It is obvious that the scattering pattern is strongly dependent on the particle size parameter, becoming more forward-directed and less polarizationdependent as the particle size parameter increases. This trend forms the basis for the diagnostic design.

A data acquisition system is described that is designed to stabilize cooling and probe rates to maximize detection sensitivity and minimize possible systematic errors due to correlations between drifting experimental conditions and varying drive parameters. Experimental parameters that affect the Yb171 5D3/2 hyperfine state preparation and detection efficiency are characterized and optimized. A set of wait times for optimal sampling of the D3/2(F=2) lifetime is chosen and used to measure that lifetime with high statistical sensitivity. A systematic variation in this lifetime seems to be apparent. The source of the variation was not identified, but ion number and cooling rate appear to be ruled out. A net determination is made of tau=61.8ms+-(0.6)_stat+-(6.4)_sys which is significantly longer than other measurements of the same quantity. An alternate shelving scheme is proposed that would provide S-D state discrimination for Yb even isotopes as well as improved sensitivity for D state hyperfine discrimination in odd isotopes.

We have employed the 12.6 GHz microwave transition resonance of a single trapped$^{171}$Yb+ ion to accurately measure the size and relative orientation of the magnetic and optical electric fields at the position of the ion in the trap. Accurate knowledge of these fields is required for precision experiments such as single ion PNC. As a proof of the principle we have measured the polarization dependent light-shift of the ground state hyperfine levels due to the 369 nm cooling laser to determine its electric field amplitude and polarization.

The beam breakup instability has long been a problem for linear induction accelerators (LIAs). Although it is predicted to saturate in the strong focus regime relevant to LIAs most, if not all, LIAs have had pulse-widths too short to observe this effect. We recently completed BBU experiments on a 1.2 kA, 6.7-MeV configuration of the DARHT-II LIA having a 1600-ns pulse length, which is much longer than the saturation time. When we reduced the magnetic guide-field strength to observe BBU, the saturated growth was in agreement with theory. We used these results to deduce that BBU growth will be insignificant in the final 2-kA, 17-MeV DARHT-II configuration with the tunes that will be used. Another problematic instability for long-pulse LIAs such as DARHT-II is the ion-hose. We also performed experiments with the 6.7-MeV long-pulse configuration of DARHT-II in which we deliberately induced ion-hose by raising the background pressure far above its normal value. The results of these experiments were used to show that ion-hose will not be a problem for to the final DARHT-II configuration.

We briefly review the development and theory of an experiment to investigate quantum computation with trapped calcium ions. The ion trap, laser and ion requirements are determined, and the parameters required for simple quantum logic operations are described. (LAUR 98-314)