FROB :: Soft and Hard X-Ray FELs: X-Ray Optics, Detectors, Absorption, Scattering, and Imaging; Closing Remarks

Date/Time: 26-Aug-05 :: 10:45—13:00
Chair: T. Ishikawa, RIKEN Spring-8 Harima, Hyogo

Paper Title Page
FROB001 Nano-Focusing of XFEL
 
  • T. Ishikawa
    RIKEN Spring-8 Harima, Hyogo
 
 

Recent advances of both light sources (undulators in 3rd generation SR sources) and optics has enabled to focus hard x-rays below 100 nm diameter. In this talk will be reviewed some recent activities toward 1 nm diameter focusing. Also will be discussed what is the size limiting parameter.

 
   
FROB002 3D Coherent X-Ray Diffraction Microscopy: the Present and the Future
 
  • J. Miao
    UCLA, Los Angeles, California
 
 

When a coherent diffraction pattern is sampled at a spacing sufficiently finer than the Nyquist frequency (i.e. the inverse of the sample size), the phase information is in principle encoded inside the diffraction pattern, and can be directly retrieved by using an iterative process. In combination of this oversampling phasing method with coherent X-rays, a novel form of diffraction microscopy has been developed to image nanoscale materials and biological systems. In this talk, I will present the principle of this microscope, discuss the current status of this research field, and illustrate some future opportunities by using X-ray free electron lasers.

 
   
FROB003 Tracking of Wavefronts 694
 
  • J. Bahrdt
    BESSY GmbH, Berlin
 
 

The design of beamlines for VUV and x-ray FEL facilities requires a detailed knowledge of the coherent radiation source. Time dependent simulations with FEL codes like GENESIS provide the electric field distribution at the end of the FEL which represents the complete information. Ray tracing codes used to transform the light from the source to the sample are generally based on geometrical optics and do not include directly the coherent properties of the FEL radiation. On the other hand Fourier optic techniques are usually applied to the propagation across normal incidence optics. We present an algorithm based on physical optics which permits the propagation of wavefronts across grazing incidence optics including interference effects, diffraction, polarization variation and pulse lengthening. Some examples are given for the proposed BESSY soft x-ray FEL.

 
   
FROB004 Diffraction Simulations of the LCLS FEL Pulse on Crystals 702
 
  • S. Reiche
    UCLA, Los Angeles, California
 
 

The Linac Coherent Light Source operates as a Self-Amplified Spontaneous Emission Free-Electron Laser (SASE FEL), where transverse coherence is achieved by the domination of the FEL Eigenmode with the largest growth rate. However complete transverse coherence is not guaranteed because there are multiple eigenmodes with similar growth rates for a low-diffracting FEL, such as the LCLS. In addition the mode purity can be degraded by collective electron beam motion. In this presentation the transverse coherence for the LCLS pulse is investigated with respect to scattering on crystals. The degradation in the contrast and size of the Bragg peaks is analysed for a step wise improved modeling of the experiment (stead-state, time-dependent and start-end simulations). The impact on diffraction experiments, including the proposed experiment to measure the transverse coherence, is discussed.