Focusing X-Rays with Curved Multiplate Crystal Cavity

Ying-Yi Chang,Shih-Lin Chang,Makina Yabashi,Shih-Chang Weng,Yuriy Stetsko,Sung-Yu Chen,Bo-Yuan Shew,Mau-Tsu Tang,Chia-Hung Chu

doi:10.1155/2010/421945

Abstract

An overview is given of the study on X-ray focusing using the Fabry-Perot type multi-plate silicon crystal cavities consisting of compound refractive lenses. Silicon (12 4 0) is used as the back reflection for cavity resonance at the photon energy of 14.4388 keV. Measurements of focal length of the transmitted beam through the crystal cavities show enhanced focusing effect due to the presence of back diffraction. Also, an incident beam with ultrahigh energy resolution can improve the focusing owing to the wider acceptance angle of the back diffraction. Considerations based on the excitation of dispersion surface within the framework of X-ray dynamical diffraction theory are also presented to reveal the origin of this enhanced focusing.

Highlights

Focusing X-rays is usually considered very difficult because the refractive index of X-rays is smaller than and very close to unity
In 1996, Snigirev et al succeeded in focusing high-energy X-rays by the so-called compound refractive lenses (CRL) of spherical shape [3]
If only a conventional double crystal monochromator is employed as the beam conditioner, the focusing is less effective than the case with an ultrahigh resolution monochromator, because the latter could fulfill cavity resonance conditions and provide a wider acceptance angle for the incident beam

Summary

Introduction

Focusing X-rays is usually considered very difficult because the refractive index of X-rays is smaller than and very close to unity. In 1996, Snigirev et al succeeded in focusing high-energy X-rays by the so-called compound refractive lenses (CRL) of spherical shape [3]. The CRL of parabolic shape have been developed to eliminate the spherical aberration and other distortion and Kinoform lenses have been used to diminish the absorption [4]. Attempts to combine this Fabry-Perot type crystal cavity with CRL lenses of circular [9] and parabolic shapes [10] for X-ray focusing have been pursued. An overview is given of this development of utilizing crystal cavities for focusing X-rays. We will first briefly describe the cavity resonance in Fabry-Perot type crystal cavity via back diffraction from perfect silicon crystals

X-Ray Fabry-Perot Resonator and Back Diffaction

Sample Preparation and Experimental Setup

Results

Theoretical Analysis

Conclusion