We report the absolute conversion efficiency ξx from the incident laser light energy to x-ray photons for laser-produced plasmas. Potential x-ray backlighting (radiography) line sources having photon energies from 1.4 to 8.6 keV are studied as a function of laser wavelength, pulsewidth, and intensity. The laser intensity and pulsewidth range from 1014 to 1016 W/cm2, 100 ps to 2 ns and include incident wavelengths of 1.06, 0.53, and 0.35 μm. We found that K-shell x-ray line emission ξx : (1) decreases with increasing x-ray energy, (2) decreases with increasing laser intensity, (3) decreases rapidly with pulselength, and (4) moderately increases with decreasing laser wavelength. On the contrary, for Au M band emission, at a fixed laser intensity and pulsewidth, ξx significantly increases (∼25×) upon decreasing the laser wavelength from 1.06 to 0.35 μm.

In three experiments, college students performed either 2-or 3-comparison conditional discriminations (arbitrary matching to sample) that utilized 64 different configurations composed of drawings. Within each configuration , one comparison related to the sample taxonomically, one related thematically, and, where there was a third comparison, it did not relate to the sample. In training phases, subjects received positive verbal feedback for selections of either the taxonomic or thematic comparisons. Between training phases, subjects responded to novel configurations similar to those of training phases on which they received no feedback for their selections. For some subjects, one cycle through all the phases ended the experiment (Experiment 1); for others, in a second cycle, verbal feedback was reversed to follow selections based on the other relation and all phases were repeated (Experiment 2); and for 1 subject, contextual stimuli indicated which relation would lead to positive verbal feedback for each selection (Experiment 3) . On test phases, the selections of all subjects became increasingly consistent with verbal feedback during training while the contextual stimuli reliably enabled the appropriate relations. These results suggest that human subjects respond relationally on this task, and that such relational responding can be contextually controlled.

Parylene (C8H8) and tungsten-glass (W2O/P2O5) disks have been irradiated with 150–400 psec Nd:YAG-glass laser pulses focused to diameters of 250–300 μm with flux levels in the 1013–1015 W/cm2 range. An extensive array of diagnostics was used to measure the temporal and energy distributions of the focused laser light at the target, the angular distribution of the scattered laser light, the x-ray spatial and spectral emission characteristics, and the emitted ion and electron distributions. Analysis of the experimental results indicates that the laser-plasma interaction was characterized by a variety of collective phenomena which appeared stronger in the tungsten-glass experiments.

Four quartz, orthogonal, cylindrical mirror pairs, two of which are coated with nickel, image the x-ray emission from laser fusion targets on hard film with a magnification of 3. K-edge filters used in conjunction with the mirror pairs permit us to take simultaneous pictures in four energy bands between 0.7 and 3.5 keV. We have measured microscope resolution, mirror reflection efficiency, and film sensitivity and used them to deduce the absolute emissivity and spectral characteristics of various laser fusion targets. This instrument is now used routinely for studying laser-generated plasmas at Lawrence Livermore Laboratory.

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