Instrumentation has been developed at the Lawrence Livermore Laboratory for measuring subkilovolt x-rays from laser-produced plasmas. This information is needed to do a complete energy balance on laser fusion experiments. The instruments must have thin windows and yet discriminate against the severe environment of other intense target emissions such as ions, electrons, and scattered laser light. Low energy x-ray measurements down to 0.1 keV will be presented using these absolutely calibrated detectors on laser target shots with the LLL Terawatt laser facility, Cyclops. Precautions in using these detectors in a laser fusion target chamber will be enumerated from our experience in using these instruments on hundreds of laser shots.

The presence of hydrodynamic fluid instability at the ablation surface puts constraints on the kinds of targets, surface finish, and energy sources that one can use for thermonuclear micro-implosions. If Taylor-like modes grow at near the classical value, one is limited to low aspect ratio shells and surface finishes of 10-100 A. These surface finish requirements can be reduced by 1 to 2 orders of magnitude by exploiting density gradient modification techniques to obtain a shallow density gradient at the ablation surface. For laser driven targets, the gradient is achieved by utilizing suprathermal electrons with a high energy ''get lost'' region to eliminate severe preheat problems. For charged particle sources, the reduction is achieved by introducing an energy spread on the driving source.

In recent years several techniques have become available to characterize the structure and chemical composition of surfaces of ceramic materials. These techniques utilize electron scattering and scattering of ions from surfaces. Low-energy electron diffraction is used to determine the surface structure, Auger electron spectroscopy and other techniques of electron spectroscopy (ultraviolet and photoelectron spectroscopies) are employed to determine the composition of the surface. In addition the oxidation state of surface atoms may be determined using these techniques. Ion scattering mass spectrometry and secondary ion mass spectrometry are also useful in characterizing surfaces and their reactions. These techniques, their applications and the results of recent studies are discussed. 12 figures, 52 references, 2 tables.

The energy carried by particles and low energy x-rays resulting from irradiation of targets with .5 to 1 TW, 1.06 ..mu..m lasers has been measured. The energy distributions were obtained from measurements at discrete locations using calorimeters and work is in progress to obtain them over a hemisphere with a thermal imaging system. Azimuthal symmetry and polar distributions for different focusing schemes have been determined. The data have been integrated to obtain the absorbed energy and these values compared to box calorimetry and optical energy balance. The relative emission of low energy x-rays from different Z materials can be obtained by comparing these data to charge collector data. Such comparisons also showed that the effective ion charge can be as low as a factor of two below the completely ionized state. The existence of low charge state ions has since been confirmed with high resolutions spectrometers.