Pinhole-array x-ray spectrometer for laser-fusion experiments

A pinhole-array x-ray spectrometer for laser-fusion experiments is demonstrated. An array of approximately 300 pinholes is placed in front of a flat-crystal spectrometer, yielding target images at photon energies ~10 eV apart (for photon energies of ~4 to 5 keV). For wideband radiation the images are two dimensional, whereas when a single spectral line is used, the field of view in the direction of dispersion is limited. However, single spectral line images can have a field of view sufficient for imaging the compressed target core. We show the image at the Ti-Kalpha-line fluorescence from a Ti-doped shell, which we show to be excited by continuum radiation from the compressed core. The Kalpha image delineates the cold, compressed shell at peak compression, which can otherwise be obtained only through backlighting. In addition, the array provides spectra of high spectral resolution because of the reduction in the effective source size.     

Gaussian content as a laser beam quality parameter

We propose the Gaussian content (GC) as an optional quality parameter for the characterization of laser beams. It is defined as the overlap integral of a given field with an optimally defined Gaussian. The definition is especially suited for applications where coherence properties are targeted. Mathematical definitions and basic calculation procedures are given along with results for basic beam profiles. The coherent combination of an array of laser beams and the optimal coupling between a diode laser and a single-mode fiber are elaborated as application examples. The measurement of the GC and its conservation upon propagation are experimentally confirmed.     

Detection of the electromagnetic field induced by the wake of a ship moving in a moderate sea state of finite depth

The wake of a ship and ambient sea waves induce disturbances in the Earth??s geomagnetic field. Numerical simulations are used to examine the feasibility of detecting these disturbances for moderate sea states. It is assumed that the electromagnetic disturbances are sampled by an air-borne magnetometer moving steadily along a rectilinear path. Spectral analysis of the samples is performed. Numerical simulations indicate that the magnetic field induced by the noisy sea environment and that by the wake of a moving ship have different spectral characteristics. Typically, the peak of the body-induced magnetic-field spectrum is located in the range of frequencies where the corresponding value of the wind wave??s spectrum is less significant. It is illustrated that the feasibility of electromagnetic detection of a ship??s wake depends strongly on the ship??s depth-based Froude number.     

Changes within vascular bundles of rodent kidneys caused by different diets

Morphological effects caused by two different diets (low protein-high water intake, and high protein-restricted water) on the vascular bundles in the outer medullary zone of the kidney were studied in the laboratory white mouse and in the golden spiny mouse (Acomys russatus, Muridae). In both rodents, when on a low protein-high water intake diet, considerable interstitial substance was found between the vasa recta of the bundles. No interstitial substance was found in animals on high protein-low water intake diet; as a result the vasa recta of the vascular bundle adhered closely. The low protein-high water intake diet caused a marked diuresis, low urine osmolality and low urinary urea concentration. It is assumed that the increase in interstitial substance between the vasa recta of the vascular bundle lowers the efficiency of the counter current barrier system for urea in the kidney and, as a consequence, the medullary urea gradient and urine concentrating capacity decreases. In animals on a high protein diet, the closely juxtaposed vasa recta assure an efficient countercurrent exchange, leading to accumulation and maintenance of a large urea gradient in the medulla and maximal urine concentration. It is suggested that the amount of interstitial material between the vasa recta of the vascular bundle might serve as a modulating factor for the urea concentration in the kidney.     

Spectroscopic modeling of an argon-doped shock-ignition implosion

We present results from the spectral postprocessing of a one-dimensional hydrodynamic simulation of an argon-doped, warm-shell shock-ignition implosion with a detailed atomic and radiation physics model. The argon tracer is added to the deuterium filling in the core for diagnostic purposes. Spectral features in the emergent intensity distribution in the photon energy range of the argon K-shell spectrum that have potential for diagnostic application are discussed.     

Crystal diffraction systems for X-ray spectroscopy, imaging, and interferometry of laser fusion targets

Recent developments in X-ray diagnosis of laser produced plasmas, involving X-ray diffraction systems, are reviewed. Three methods currently under development are described: 1) Von Hamos focusing crystal X-ray spectrograph, 2) Laue crystal spectrograph and imaging devices, and 3) X-ray interferometry crystal devices. Some of the results shown are 1) a method of using mosaic crystals in a geometry which yields both high sensitivity and resolution; 2) ionic spectral lines of higher energy (12-14 keV) than has been previously observed; and 3) two-dimensional achromatic Laue imaging ofsim 10mum resolution.     

Focusing x-ray spectrograph for laser fusion experiments

X-ray spectra from laser fusion targets are normally measured with flat crystal (nonfocusing) spectrographs. We describe here the characteristics of a focusing spectrograph which is capable of recording wide band spectra with significantly higher sensitivity. Measuring spectra in the (10-11) A range from glass microballoons imploded by a two-beam Nd:Glass laser system we find intensity per unit area on film about 100 times higher with a curved mica than with a flat mica spectrograph.