Novel techniques and standards for X-ray spectrometry and tests of QED
AuthorSmale, Lucas Francis
AffiliationSchool of Physics
MetadataShow full item record
Document TypePhD thesis
Access StatusOpen Access
© 2016 Dr. Lucas Francis Smale
This thesis advances the standards and techniques used in x-ray spectrometry for laboratory sources and advanced sources, such as Electron Beam Ion Traps (EBITs). This impacts upon popular fields including x-ray diffraction, x-ray absorption spectroscopy and advanced quantum mechanics. A new method of removing cosmic ray signals from CCD detectors in a low ux environment is presented. New characterizations of Ti Kß and V Kß, to be used as calibration standards, are presented. Preliminary measurements of lines of He-like Cr lines were performed to test QED. Different types of x-ray spectrometry are important in fields such as testing Quantum Electrodynamics (QED) in the x-ray regime and the study of the local environment of atoms in the solid state through X-ray Absorption Fine Structure (XAFS). Tests of QED require highly accurate and precise determination of x-ray energy from low ux sources, while advances in XAFS studies require the ability to properly determine the validity of results. This research develops techniques and standards in spectrometry for use in XAFS and tests of QED. Further, these techniques are used to test QED. The previous standard method of fitting XAFS did not use measured uncertainties, thus they could not be propagated to the results. Fitting via the minimisation of the statistically valid reduced-χ-squared measure of goodness of fit enables error bars to be propagated. A statistically valid reduced-χ-squared measure of goodness of fit was applied to the previous standard method of XAFS fitting. This improvement also allowed for a more robust interpretation of XAFS fitting parameters and the testing of XAFS theory. This new fitting method was applied to the K-edge XAFS of molybdenum. It was found that the XAFS theory and experiment where inconsistent with each other. New theory is necessary. CCD detectors in a low ux environment have been used for tests of QED. In such situations, distinguishing between signal caused by cosmic rays and a low ux of x-ray photons from the desired source would enable higher precision tests of QED. This work presents a new method of removing the signal caused by cosmic rays from x-ray CCD detector spectra. A new method of calibrating a Johann curved crystal spectrometer is presented, and used to create new characterizations of Ti Kß and V Kß. These characterizations can be used for the calibration of x-ray spectrometers employed for tests of QED. The V Kß peak energy was found to be 5426.962(15) eV. This is an improvement in uncertainty by a factor of 4.7 over prior work. The Ti Kß peak energy was found to be 4931.966(22) eV, an improvement in uncertainty by a factor of 2.6 over the previous best reported result. The limits of the calibration method were tested by measuring Cr Kß, which was on the limit of the calibrated energy range. Preliminary measurements of the w, x, y and z lines of He-like Cr were performed to test QED. The w line energy was measured to be 5682.049(30)(200) eV, a factor of just under two improvement over previous measurements. The energies of the x, y and z lines were found to be 5664.425(73)(200) eV, 5654.232(68)(200) eV and 5626.305(42)(200) eV respectively. These energies had not previously been measured.
Keywordsquantum electrodynamics; atomic physics; X-rays; X-ray spectrometry; advanced relativistic quantum mechanics; synchrotron science; electron beam ion traps
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