Leslie A. Welser

Changes in absorbance of monolayer of living cells induced by laser radiation at 633, 670, and 820 nm

Redox absorbance changes in living cells (monolayer of HeLa cells) under laser irradiation at 633, 670, and 820 nm have been studied by the method of multichannel recording in spectral range 530-890 nm. It has been found that the irradiation causes changes in the absorption spectrum of the cells in two regions, near 754-795 nm (maxima at 757, 775, and 795 nm) and near 812-873 nm (maxima at 819, 837, 858, and 873 nm). Changes occur in band parameters (peak positions, width, and integral intensity). Virtually no changes occur in the red spectral region and a few changes are recorded in the green region near 556-565 nm. The results obtained evidence that cytochrome c oxidase becomes more oxidized (which means that the oxidative metabolism is increased) due to irradiation at all wavelengths used. The results of present experiment support the suggestion (Karu, Lasers Life Sci., 2:53, 1988) that the mechanism of low-power laser therapy at the cellular level is based on the electronic excitation of chromophores in cytochrome c oxidase which modulates /spl alpha/ redox status of the molecule and enhances its functional activity.

Multispectral X-Ray Imaging With A Pinhole Array And A Flat Bragg Mirror

We describe a multiple monochromatic x-ray imager designed for implosion experiments. This instrument uses an array of pinholes in front of a flat multilayered Bragg mirror to provide many individual quasi-monochromatic x-ray pinhole images spread over a wide spectral range. We discuss design constraints and optimizations, and we discuss the specific details of the instrument we have used to obtain temperature and density maps of implosion plasmas.

Processing of multi-monochromatic x-ray images from indirect drive implosions at OMEGA

We report here on the processing of multi-monochromatic x-ray images recorded with the MMI instrument in a series of stable and low-convergence indirect-drive implosion experiments in which Ar-doped D2-filled plastic shells were imploded with the OMEGA laser system. MMI records numerous narrow-band x-ray images over a broad photon energy range. From these images, specific line- and continuum-based subimages can be extracted. A procedure for processing data from the array of images recorded by MMI was developed and implemented into a convenient interactive data language code. Data from narrow-band x-ray images are critical for diagnosing the spatial structure of ICF implosion cores.

Multispectral x-ray imaging for core temperature and density maps retrieval in direct drive implosions

We report on the experiments aimed at obtaining core temperature and density maps in direct drive implosions at the OMEGA Laser Facility using multi-monochromatic X-ray imagers. These instruments use an array of pinholes and a flat multilayer mirror to provide unique multi-spectral images distributed over a wide spectral range. Using Argon as a dopant in the DD-filled plastic shells produces emission images in the Ar He-b and Ly-b spectral regions. These images allow the retrieval of temperature and density maps of the plasma. We deployed three identical multi-monochromatic X-ray imagers in a quasi-orthogonal line-of-sight configuration to allow tomographic reconstruction of the structure of the imploding core.

Analysis of the spatial structure of inertial confinement fusion implosion cores at OMEGA

We report on an experimental and modeling study of the spatial structure in indirectly driven implosion cores. To this end, Ar-doped D2-filled plastic shells were irradiated with the OMEGA laser system. We focus on processing and analysis of data recorded with a new X-ray imager (MMI-2) that records numerous narrow-band images that include both line and continuum emission. The temperature and density gradients are determined by using a multi-objective analysis of X-ray narrow-band images and X-ray line spectra. This analysis self-consistently determines the temperature and density gradients that yield the best fits to the spatially-resolved emissivity and space-integrated spectral line shapes.

Multiobjective method for fitting pinhole image intensity profiles of implosion cores driven by a Pareto genetic algorithm

We discuss a method for the simultaneous and self-consistent fitting of a set of intensity or emissivity spatial profiles from several narrow-band x-ray pinhole images from argon-doped inertial confinement fusion implosion cores, and the space-integrated line spectrum. A Pareto genetic algorithm (PGA) combines the search and optimization capabilities of a single-objective genetic algorithm with the Pareto domination technique of multiobjective optimization. Further, the PGA search is followed up by a fine-tuning step based on a nonlinear least-squares-minimization procedure. The result is a robust search and reconstruction method that finds the optimal core spatial structure subject to multiple constraints. This method is independent of geometry inversions and could take advantage of not only optically thin but also optically thick image data. Results are shown for two combinations of three-objectives based on gated argon Heβ and Lyβ image data and the line spectrum.

Numerous applications of fiber optic evanescent wave Fourier transform infrared (FEW-FTIR) spectroscopy for subsurface structural analysis

A new infrared (IR) interferometric method has been developed in conjunction with low-loss, flexible optical fibers, sensors, and probes. This combination of fiber optical sensors and Fourier Transform (FT) spectrometers can be applied to many fields, including (1) noninvasive medical diagnostics of cancer and other different diseases in vivo, (2) minimally invasive bulk diagnostics of tissue, (3) remote monitoring of tissue, chemical processes, and environment, (4) surface analysis of polymers and other materials, (5) characterization of the quality of food, pharmacological products, cosmetics, paper, and other wood-related products, as well as (6) agricultural, forensic, geological, mining, and archeological field measurements. In particular, our nondestructive, fast, compact, portable, remote and highly sensitive diagnostics tools are very promising for subsurface analysis at the molecular level without sample preparation. For example, this technique is ideal for different types of soft porous foams, rough polymers, and rock surfaces. Such surfaces, as well as living tissue, are very difficult to investigate by traditional FTIR methods. We present here FEW-FTIR spectra of polymers, banana and grapefruit peels, and living tissues detected directly at surfaces. In addition, results on the vibrational spectral analysis of normal and pathological skin tissue in the region of 850 - 4000 cm-1 are discussed.

Spatial structure analysis of direct-drive implosion cores at OMEGA using x-ray narrow-band core images

The spectroscopic analysis of x-ray narrow-band images and space-integrated x-ray line spectra from argon-doped deuterium-filled inertial confinement fusion implosion experiments yields information about the spatial profiles in the compressed core. We discuss the analysis of direct-drive implosion experiments at OMEGA, in which images were obtained with a multimonochromatic imaging instrument. The analysis method considers data based on the argon Heβ and Lyβ spectral features and their associated Li- and He-like satellites. The temperature gradient structure is investigated by using the sensitivity of the Lyβ∕Heβ emissivity ratio to the temperature.

Narrow-band x-ray imaging for core temperature and density maps retrieval of direct drive implosions

We present recent results using multi-monochromatic X-ray imaging of direct drive implosions at the OMEGA laser facility. An array of pinholes coupled to a flat multilayer mirror provides multi-spectral images distributed over a wide spectral range. Using Argon as a dopant in the DD-filled plastic shells produces emission images in the Ar He-β and Ly-β spectral regions. When used in conjunction with gated imaging detectors the instrument provides images with spatial resolution of ~10μm and temporal resolution of ~50ps. A special algorithm has been developed to reconstruct narrow-band images, which will allow the retrieval of temperature, and density maps of the core as it evolves through peak compression.

Core Temperature and Density Gradients in ICF

We have developed a multiple monochromatic x‐ray imaging diagnostic that uses an array of pinholes coupled to a multilayer Bragg mirror, and we have used this diagnostic to obtain unique multispectral imaging data of inertial‐confinement fusion implosion plasmas. Argon dopants in the fuel allow emission images to be obtained in the Ar He‐β and Ly‐β spectral bands, and these images provide information on core temperature and density profiles. We have analyzed these images to obtain quasi‐three‐dimensional maps of electron temperature and scaled electron density within the core for several cases of drive symmetry, and we find quantitative and qualitative disagreement with one‐dimensional hydrodynamics simulations. We also observed a two‐lobed structure evolving for increasingly prolate‐asymmetric drive.