Journal of X-Ray Science and Technology - Volume 3, issue 4

Authors: MacGowan, B. J. | Mrowka, S. | Barbee Jr., T. W. | da Silva, L. B. | Eder, D. C. | Koch, J. A. | Pan, L. S. | Turner, J. A. | Underwood, J. H. | Young, P. E.

Article Type: Review Article

Abstract: In many applications, multilayer mirrors are exposed to damaging fluences of x rays. In x-ray laser cavities intense optical and broad-band x radiation, from the x-ray laser plasma amplifier, can damage multilayer mirrors on time scales of hundreds of picoseconds. We describe experiments using short duration (500 ps) bursts of soft x rays from a laser produced gold plasma to damage multilayer mirrors designed to reflect wavelengths close to 45 Å at normal incidence. The effect of the damaging x-ray flux on normal incidence reflectivity was time resolved for W/C, WRe/C, WC/C, 303-stainless-steel/C, and Cr3 C2 /C multilayers. The damage …thresholds of the different mirrors were compared, and the Cr3 C2 /C mirrors were found to be the most resilient. The outer layers of the multilayers were observed to expand slowly as x rays were absorbed, and a more rapid expansion then preceded the total loss of reflectivity, at temperatures well below the melting temperature of the mirror components. It is believed that the dominant expansion mechanism is a change in the amorphous carbon layers to a more graphitic structure. The data are fit quite well by a model that assumes expansion of up to 25% in the thickness of the outermost carbon layers, followed by intermixing of the hotter layers. The rapid expansion has been observed to occur in times from 40 to 150 ps and may be the fastest resolution to date of the phenomenon of graphitization. The integrated reflectivity of the mirrors was observed to increase by up to a factor of 2.5 as they damaged; this reflectivity increase may be consistent with a reduction in the layer roughness. Show more

DOI: 10.3233/XST-1992-3401

Citation: Journal of X-Ray Science and Technology, vol. 3, no. 4, pp. 231-282, 1992

Authors: Gullikson, E. M. | Underwood, J. H. | Batson, P. C. | Nikitin, V.

Article Type: Research Article

Abstract: A soft x-ray reflectometer is described which is based on a laser-produced plasma source and is continuously tunable over the range 40 Å < λ < 400 Å. The source is produced by focusing 0.532-μm light from a Q-switched Nd:YAG laser on a solid target. The x-ray wavelength is defined using a high throughput spherical grating monochromator with moderate resolving power (λ/Δλ ≈ 100 to 500). A time-averaged monochromatized flux of more than 109 photons/s in a 1% bandwidth at 100 eV is obtained. Photon “shot noise” limited measurements are obtained by the use of an I0 detector …to normalize out the shot-to-shot variations in source intensity. Measurements with submillimeter spot sizes are readily obtainable. Various detectors have been used and the advantages and disadvantages of each are discussed. The higher order contamination of the monochromator output has been analyzed using a second grating for the purpose of making measurement corrections. The reflectometer thus provides the capability for precision absolute measurements of the reflectance of gratings and multilayer mirrors, the transmittance of thin film filters, or other properties of x-ray optical elements. Show more

DOI: 10.3233/XST-1992-3402

Citation: Journal of X-Ray Science and Technology, vol. 3, no. 4, pp. 283-299, 1992

Authors: Zukowski, E. | Cooper, M. J. | Armstrong, R. | Ito, M. | Collins, S. P. | Laundy, D. | Andrejczuk, A.

Article Type: Research Article

Abstract: The magnetic form factor of nickel has been measured, as a fraction of the charge form factor for {h00} and {hhh} reflections up to (10 00) and (666), by an x-ray energy dispersive white beam technique that uses elliptically polarized synchrotron radiation and single crystal samples. At low sin(θ)/λ the results are in good agreement with theory and with the values determined from neutron studies. The measurements extend beyond the current range of neutron data and indicate that significant magnetic diffraction effects are observable at sin(θ)/λ > 1.5 Å−1 if photons with energies above 26 keV can be used.

DOI: 10.3233/XST-1992-3403

Citation: Journal of X-Ray Science and Technology, vol. 3, no. 4, pp. 300-310, 1992

Authors: Burge, R. E. | Buckley, C. J. | Foster, G. F. | Miller, A. | Wess, T.

Article Type: Research Article

Abstract: Using a Fresnel zone plate we demonstrate for the first time the direct visualization by x-ray microscopy of suboptical regularity in a biological specimen, namely the 65-nm axial periodicity of tendon collagen. This resolution test demonstrates a resolving power of about 20λ; a resolving power of <10λ is in prospect.

DOI: 10.3233/XST-1992-3404

Citation: Journal of X-Ray Science and Technology, vol. 3, no. 4, pp. 311-314, 1992