A suite of computer routines is presented that uses scalar wavefront theory to calculate the propagation of arbitrarily-shaped x-ray wavefronts through a series of objects and drift spaces that represent an experiment...
详细信息
ISBN:
(纸本)0819454745
A suite of computer routines is presented that uses scalar wavefront theory to calculate the propagation of arbitrarily-shaped x-ray wavefronts through a series of objects and drift spaces that represent an experimental setup. The routines are coded in IDL, the Interactive Data Language, and can be included into or extended with any other IDL code. Objects and apertures in the x-ray path are modeled in the thin-object approximation, where they are represented by a two-dimensional complex transmission function. Fresnel propagation through drift spaces is carried out in Fourier space in the paraxial approximation. A variety of predefined, ready-for-use objects is included in the package. Among these are optical elements such as gratings, lenses, slits, or pinholes, as well as reference sample objects such as spheres, cylinders, test grids, etc. The materials and geometrical parameters of these objects can be freely chosen. Optical materials constants are looked up automatically in the DABAx database. The modular structure of the code makes it reasonably easy for users to add support for objects of any degree of complexity, or even other propagation schemes.
neutron guides are widely used for improving the angular aperture of neutron scattering instruments in a broad band of wavelength. However, the usual guides are not effective enough in the short wavelength range. This...
详细信息
ISBN:
(纸本)0819454745
neutron guides are widely used for improving the angular aperture of neutron scattering instruments in a broad band of wavelength. However, the usual guides are not effective enough in the short wavelength range. This is especially critical for time-of-flight instruments, which cannot take advantage of focusing techniques designed for steady-state monochromatic instruments. We discuss alternative ways to shape the reflecting surfaces in order to obtain a maximum angular aperture at the sample position at the expense of beam cross-section reduction. An optimal piecewise solution is proposed and Monte Carlo simulations with the IDEAS package are presented. Simulations for General Purpose Powder Diffractometer (GPPD) at Argonne National Laboratory are presented and the impact of a vertically focusing multiple-stage tapered guide is discussed. The results obtained by simulating the guide system options of engineering diffractometer VULCAN at the Spallation neutron Source (SNS) are also presented, including vertically and horizontally tapered guide sections. The optimal multi-stage tapered guide design is discussed in terms of instrument figure of merit corresponding to different experimental needs ranging from high Q resolution to high intensity and/or high spatial resolution.
A number of future hard x-ray (10-100 keV) telescopes will implement focusing optics with multilayer coatings. In this framework, we are developing (at INAF/Brera-Merate Astronomical Observatory) multilayer optics bas...
详细信息
A number of future hard x-ray (10-100 keV) telescopes will implement focusing optics with multilayer coatings. In this framework, we are developing (at INAF/Brera-Merate Astronomical Observatory) multilayer optics based on the e-beam deposition technique: this approach is suitable to coat very large surfaces at an high deposition rate;in order to test the performances of the deposited samples, x-ray reflectivity scans at the two "standard" photon energies of 8.05 and 17.4 keV are taken, returning very positive results with high peak reflectivities. However, the exact interpretation of the reflectivity curves is a complex task since it depends on a large number of parameters: the software PPM (Pythonic Program for Multilayers) has been recently developed by A. Mirone (ESRF) specifically to the aim of a friendly and fast determination of the parameters of multilayer structures. In particular, for this paper we present the layer-by-layer modelization of the characteristics (roughness, density, thickness) of multilayer stacks (Ni/C, Pt/C) by a multi-parametric "global" automatic optimization to reach the best fitting performances. In order to physically constrain the parameters, the data will be compared with the results of TEM measurements performed on the same samples, when available.
暂无评论