Hard x-ray microanalysis with parabolic refractive lenses

Since their discovery by Wilhelm Conrad Röntgen in 1895 X-rays have been used in analytical applications. Most common, X-rays are known as medical diagnostic tools due to their ability to non-destructively pass through matter which cannot be penetrated by visible light. Hard X-rays cover the energy range from about 1 keV to 200 keV. In this energy region fluorescence radiation and absorption spectroscopy of bulk samples is possible. Likewise, hard X-ray crystallography gives information of the inner structure of materials. As powerful as these analytical methods are, many applications need a focused X-ray beam. Especially, heterogeneous samples and complex structures benefit from the higher spatial resolution of a micro focused beam. However most optics become less efficient with higher X-ray energies. This thesis follows the development of microanalysis in the hard X-ray range based on parabolic refractive lenses. Obviously, refractive lenses for visible light are most successful. But the weak refraction and strong absorption of hard X-rays in matter make the realization of refractive lenses difficult. Highly brilliant X-ray sources and advanced instrumentation are the foundation for the first experiment, which used refractive X-ray lenses, by Snigirev et al. in 1996. The aperture of refractive lenses for hard X-rays is comparable to their radius of curvature. Therefore, spherical refractive lenses suffer from aberration and are not appropriate for microscopy and other imaging applications. Parabolic refractive hard X-ray lenses have solved this problem. A full field hard X-ray microscope which used a stack of parabolic refractive aluminium lenses was first implemented in Aachen. Three topics in the development of parabolic refractive lenses are introduced in this thesis: the use of beryllium parabolic refractive lenses in hard X-ray microanalytic is demonstrated, XANES microtomography has been implemented, and a concept for nanofocusing with parabolic refractive lenses has been developed. To improve the imaging application of refractive lenses and to enhance the energy range parabolic beryllium lenses were manufactured. Beryllium as lens material improves the transmission of the refractive lenses and increases the field of view. This is favorable for microfocusing, and helps to improve microtomography. Beryllium lenses are optimal for energies between 5 keV and 40 keV. With a full field microscope a lateral resolution of 140 nm has been achieved. The enhanced transmission of beryllium lenses as well as the flexibility and the straight optical path of parabolic refractive lenses were helpful in the implementation of XANES microtomography. This combination of near edge absorption spectroscopy with two dimensional scanning microscopy allows to examine the chemical state and the local environment of a given atomic species in a virtual slice through a sample without really cutting it. The demand for X-ray microprobes with still smaller spot size is growing. For this reason nanofocusing refractive lenses have been designed in Aachen, whose radius of curvature are 0.002 mm. A prototype of silicon is presented, which was able to achieve a resolution below 100nm, further improvements promise a resolution of even below 50nm. In summary, parabolic refractive X-ray lenses have greatly improved our capability to combine imaging techniques with spectroscopies, as more and more required in many fields of science and technology. Berylluim lenses are commonly used at 3. generation synchrotron facilities, now.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Kuhlmann, Marion

Contributors dc:contributor

• Lengeler, Bruno

• info:eu-repo/classification/ddc/530
• Harte Röntgenstrahlung
• Mikroanalyse
• Röntgenlinse
• Beryllium
• Physik
• X-Ray Oprics
• Microanalysis
• Tomography

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121460%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59698