Advances in Energy Sensitive X-ray Phase Contrast Measurements

Abstract

This dissertation represents, to our knowledge, the development and test of the firsttable-top energy resolving X-ray refractometer. Energy dependent index decrement, δ, values are extracted for several materials over a range of energy values. The experimental apparatus uses a Micro X-ray Inc. microfocus source with a focal spot size of 0.0647 mm x 0.0808 mm operated at 50 kV and 0.2 mA for a total power of 10 W. The X-ray beam is collimated to a pencil beam approximately 0.2 mm in diameter in the object plane. The objects are 50.8 mm x 50.8 mm rectangular prisms, which are angularly rocked in a sinusoidal pattern. The X-ray beam refracts off the object and travels more than 2.4 m to the detector. The detector is a prototype Redlen LD3010 EDP detector, which is an energy resolving and photon counting detector with 0.34 mm pixels, an energy resolution of 8 keV, and an energy range of 16 to 256 keV. Images of the resulting spot on the detector are acquired in 8 keV energy bins with center energies of 29 keV, 37 keV, 45 keV, and 53 keV. The types of materials tested with this refractometer include plastics, natural materials, and edible materials, all with δ values in the range of approximately 10^-7 to 10^-6. In addition to development and test of the refractometer, this dissertation also presents three additional results: (1) A signal extraction approach for estimating δ from the experimental methods. This approach proposes that rotating a steep phase gradient in a predetermined sinusoidal pattern will remove additional sources of noise and bias and isolate the influence of refraction. (2) A robust simulation of this energy sensitive refractometer. This simulation is used to initially validate the approach and further corroborate the experimental results. (3) The proposal and initial testing of an energy-based method for phase contrast imaging. This method is called Spectrally Responsive Edge Illumination and was intended to increase the feasibility and applicability of X-ray Phase Contrast Imaging by removing strict spatial requirements.