DEVELOPMENT OF A COLLIMATING CHANNEL ARRAY OPTIC FOR 3D MICROSCOPIC X-RAY FLUORESCENCE
Agyeman-Budu, David Nana
A novel x-ray collection optic called the Collimating Channel Array (CCA) for high resolution, 3D microscopic x-ray fluorescence (3D-μXRF) microscopy is developed. In material systems where sampling and sectioning is impossible, 3D-μXRF enables nondestructive spatial elemental mapping and spectroscopy for both technologically important and naturally occurring samples. Confocal x-ray fluorescence (CXRF) is one route to achieve 3D-μXRF. However, with current x-ray optics, the resolution of the micro-probe varies with the characteristic fluorescent x-ray energy of the elements present in the sample. CCAs were developed to solve the energy dependent resolution problem. This thesis describes the design, fabrication and characterization of the CCA optics. Additionally, experimental applications of the CCA optics in a CXRF setup at the Cornell High Energy Synchrotron Source (CHESS) and the Advanced Photon Source (APS) are discussed. First, the basic principles governing the theory of operation of CXRF are examined within the context of designing CCA optics. This will also cover the practical design limitations and how that has impacted the iterative improvements implemented from the initial concept through to the current generation of optics. Second, the manufacture of the CCA optics using microfabrication techniques and deep reactive etching (DRIE) is discussed. Two etch experiments: understanding how to compensate for deep etched artifacts and comparing the etching mechanisms between silicon and germanium are presented. X-ray characterization experiments are then used to analyze the performance of the optics. Third, successful experimental applications involving the use of the CCA optics are presented. These are: elemental imaging of a rice bran, elucidating the corrosion mechanisms in via depth resolved confocal x-ray absorption spectroscopy of a 13th century stained glass window from the Paderborn Cathedral in Germany, and elemental mapping to correlate lead deposits and microstructure of an archaeological human bone sample excavated from the Royal Naval Hospital cemetery (ca. A.D. 1793-1822). Finally, adopting CCA microfabrication techniques, details of the development of another new kind of x-ray optic: a platinum/SU-8 bilayer x-ray transmission mirror is introduced. Thus, this thesis will present a blueprint for a microfabricated approach in developing and implementing novel x-ray optics for x-ray beamlines.
Physics; Materials Science; confocal XRF; cultural heritage; germanium etching; transmission mirrors; x-ray fluorescence; x-ray optics; Nanotechnology
Brock, Joel Donald
Van Dover, Robert B.; Gruner, Sol Michael; Woll, Arthur R.
Materials Science and Engineering
Ph.D., Materials Science and Engineering
Doctor of Philosophy
dissertation or thesis