Bipyridine ligands containing pendant methyl, amino and amino-boronic acid groups were synthesized. Coordination complexes of these ligands with ruthenium were prepared straightforwardly and in good yield. The luminescence behavior of the Ru complexes was studied as a function of pH and exposure to various concentrations of glucose. The methyl bipyridine complex showed no change in luminescence with pH; the amino derivative showed a rapid decrease from low pH to neutral, and the amino-boronate derivative showed a gradual decrease from pH 4 to 10. Luminescence quenching was observed at high pH as expected on the basis of a photoinduced electron transfer (PET) signaling mechanism. This behavior can be explained on the basis of the first oxidation and reduction potentials of these complexes. Glucose testing showed a significant dependence on the solvent system used. In pure methanol, the ruthenium boronate complex exhibits a 4 and 10% luminescence intensity increase upon increasing glucose concentration from 0 to 400 and 0 to 1600mg/dl, respectively. However, in 50vol.% methanol/phosphate buffered saline, none of the complexes showed significant response in the glucose range of physiological interest.

Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using an ultrashort pulse laser (USPL). Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so bone tissue is selectively ablated while preserving the spinal cord.

Experimental evidence for the acceleration of electrons in a relativistic plasma wave generated by Raman forward scattering (SRS-F) of a single-frequency short pulse laser are presented. A 1.053 /spl mu/m, 600 fsec, 5 TW laser was focused into a gas jet with a peak intensity of 8/spl times/10/sup 17/ W/cm/sup 2/. At a plasma density of 2/spl times/10/sup 19/ cm/sup -3/ 2 MeV electrons were detected and their appearance was correlated with the anti-Stokes laser sideband generated by SRS-F. The results are in good agreement with 2-D PIC simulations. The use of short pulse lasers for making ultrahigh gradient accelerators is explored.

We describe the apparatus used to measure the spectrum of accelerated electrons from a laser-plasma acceleration experiment carried out a Rutherford Appleton Laboratories (RAL). The source of the broadband, energetic electrons was the forward Raman scattering instability of a high intensity (5/spl times/10/sup 18/ W/cm/sup 2/) laser. Here the laser beam photons decay into scattered photons and a relativistic electron plasma wave. The plasma wave subsequently accelerates plasma electrons to relativistic energies. The spectrometer and detectors were designed to give a quantitative (in energy and flux) single-shot electron spectrum over as wide a range of energies as possible. In this paper we present some calibration measurements taken prior to the RAL run which agree very well with TRACE3D runs used to model the beam transport. The silicon surface barrier detector (SBD) arrangement and fluorescer-filmpack arrangement are also described. Finally, some preliminary results are obtained which show excellent agreement between the spectra obtained with the SBDs and the film.

Nearly 10 years of Nova [E. M. Campbell, Laser Part. Beams 9, 209 (1991)] experiments and analysis have lead to a relatively detailed quantitative and qualitative understanding of radiation drive in laser-heated hohlraums. Our most successful quantitative modeling tool is two-dimensional (2-D) LASNEX numerical simulations [G. B. Zimmerman and W. L. Kruer, Comments Plasma Phys. Controlled Fusion 2, 51 (1975)]. Analysis of the simulations provides us with insight into the physics of hohlraum drive. In particular we find hohlraum radiation conversion efficiency becomes quite high with longer pulses as the accumulated, high-Z blow-off plasma begins to radiate. Extensive Nova experiments corroborate our quantitative and qualitative understanding.

Raman forward scattering (RFS) is observed in the interaction of a high intensity (>10/sup 18/ W/cm/sup 2/) short pulse (<1 ps) laser with an underdense plasma (n/sub e//spl sim/10/sup 19/ cm/sup -3/). Electrons are trapped and accelerated up to 44 MeV by the high-amplitude plasma wave produced by RFS. The laser spectrum is strongly modulated by the interaction, showing sidebands at the plasma frequency. Furthermore, as the quiver velocity of the electrons in the high electric field of the laser beam becomes relativistic, various effects are observed which can be attributed to the variation of electron mass with laser intensity.

The propagation of an intense, subpicosecond laser pulse through a substantial length $(L/\ensuremath{\lambda}\ensuremath{\sim}{10}^{3})$ of an underdense plasma $({n/n}_{c}\ensuremath{\sim}1%)$ is studied through experiments and computer simulations. For $I\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}8\ifmmode\times\else\texttimes\fi{}{10}^{17}$ W/c${\mathrm{m}}^{2}$ only 55% of the incident laser light was transmitted through the plasma within the focal cone angle. The decrease in transmission was accompanied by Raman forward scattering as evidenced by the generation of anti-Stokes sidebands and up to 2 MeV electrons. Simulations show that the majority of the reduction in transmission could be due to Raman forward and side scattering.

A novel linear gas jet has been developed and used to produce centimeter-scale, 1019 cm−3 electron density plasmas. Long regions of high density are important to many types of experiments, including x-ray laser and laser-plasma interaction studies. This new type of gas jet has been characterized by stimulated Raman backscatter emission from the plasma.

ELECTRONS in a plasma undergo collective wave-like oscillations near the plasma frequency, These plasma waves can have a range of wavelengths and hence a range of phase velocities(1). Of particular note are relativistic plasma waves(2,3), for which the phase velocity approaches the speed of light; the longitudinal electric field associated with such waves can be extremely large, and can be used to accelerate electrons (either injected externally or supplied by the plasma) to high energies over very short distances(2-4). The maximum electric field, and hence maximum acceleration rate, that can be obtained in this way is determined by the maximum amplitude of oscillation that can be supported by the plasma(5-8). When this limit is reached, the plasma wave is said to 'break'. Here we report observations of relativistic plasma waves driven to breaking point by the Raman forward-scattering instability(9,10) induced by short, high-intensity laser pulses, The onset of wave-breaking is indicated by a sudden increase in both the number and maximum energy (up to 44 MeV) of accelerated plasma electrons, as well as by the loss of coherence of laser light scattered from the plasma wave.

The indirect drive method of inertial confinement fusion uses a high-Z radiation case to convert energy from high-powered laser beams to x rays which implode fusion capsules. Experiments have been performed on the Nova laser to characterize the x-ray production in high-Z cavities for studying the efficiency for x-ray production using two methods for characterization. One method measures the shock velocity produced in low-Z materials by the radiation. The shock velocity is measured by observing the optical signal from the rear of a stepped or continuously varying thickness of Al placed over a hole in the cavity wall. The other method measures the reradiated x-ray flux from the cavity wall viewing through a hole in the cavity. Both methods have been shown to provide a consistent characterization of the x-ray drive in the cavity target.