• Optics and Precision Engineering
  • Vol. 15, Issue 12, 1908 (2007)

Abstract

Because the photon flux of laser-based X-ray sources is considerably lower than that of synchrotron radiation sources and radiation is emitted isotropic in all directions,focusing optics with a large solid collecting angle and high integral reflectivity are required.For these requirements crystals of Pyrolytic Graphite(PG)are of particular interest for the use as dispersive and focusing elements.Due to the mosaic crystal structure,PG exhibits a very high integral reflectivity.Furthermore,thin PG films give the opportunity to realize crystal optics with arbitrary geometry by mounting them on a mold of any shape.Beyond that,mosaic focusing in specific geometry allows these crystals to be used as high resolution X-ray optics,even in bent geometry.All these properties allow the design of highly efficient dispersive collecting optics for uhrafast X-ray spectroscopy with laser plasma sources.In our contribution we describe the application of bent PG crystals in a spectrometer with a modified Von HAMOS geometry.Using this spectrometer,the spectral distribution of the X-ray radiation emitted from a fs laser produced plasma has been measured.The application of this radiation for timeresolved Extended X-ray Absorption Fine Structure(EXAFS)experiments is discussed. We show that,by optimizing both the crystal properties and the spectrometer geometry,a good spectral resolution sufficient for EXAFS measurements at the K-edges of transition metals can be achieved.