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Studies of Light Element X-Ray Fundamental Parameters Used in PIXE Analysis

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Title: Studies of Light Element X-Ray Fundamental Parameters Used in PIXE Analysis
Author: Heirwegh, Christopher Michael
Department: Department of Physics
Program: Physics
Advisor: Campbell, John L. (Iain)
Abstract: New measurements of fundamental parameters (FP), used in reference-free particle induced X-ray emission (PIXE) analysis of materials, may be assisted by incorporating both state-of-the-art spectral processing methods and methodologies that have minimal reliance upon other FPs. Under this heading, several light element FPs have been investigated. A collection of monochromatic spectra[73] have been characterized in terms of the origins and lineshapes of features arising due solely to photon and electron interactions in the silicon detector crystal. Through the assistance of Monte Carlo simulation results, state-of-the-art fit treatments were applied to these spectra using a fit routine that combined both non-linear least squares and manual optimization. The fitted spectra were used to derive a new estimate of the K X-ray fluorescence yield (ωK) of Si. This was done using a geometrical expression that relates ωK to the area ratio of the escape to primary peaks taken from the spectra. The final result (0.0504 ± 0.0015) was realized through assistance from new low energy mass-attenuation coefficient (MAC) data. The accuracy of low-energy (1–2 keV) MACs of light elements was assessed using an approach incorporating PIXE measurements on pure element (Mg, Al and Si) and oxide (MgO, Al2O3 and SiO2) targets. Calculated spectrometer efficiency constants, compared between target pairs (eg, Si vs. SiO2), allow many FPs to cancel. Any non-zero difference in the comparison indicates errors associated with the remaining FPs. A resultant 4–6% discrepancy was attributed to the use of XCOM[10] MACs but this was reduced to 0.5–2.5% using FFAST[33] MACs. Additional measurements, performed on silicate micro-probe standards, were analyzed using the same comparative approach. A light element efficiency-constant discrepancy of 7–9% was observed and attributed to the use of XCOM MACs. This was reduced to 0.5–3.5% using FFAST MACs but was reduced further to −0.5–2% using a combination of XCOM and FFAST MACs. This result suggested that the combination database was superior.
Date: 2014-04
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Files Size Format View Description
MAC_1_H.csv 725bytes Microsoft Excel View/Open MAC_Hydrogen
MAC_8_O.csv 7.858Kb Microsoft Excel View/Open MAC_Oxygen
MAC_9_F.csv 3.247Kb Microsoft Excel View/Open MAC_Fluorine
MAC_11_Na.csv 6.236Kb Microsoft Excel View/Open MAC_Sodium
MAC_12_Mg.csv 6.008Kb Microsoft Excel View/Open MAC_Magnesium
MAC_13_Al.csv 6.499Kb Microsoft Excel View/Open MAC_Aluminum
MAC_14_Si.csv 19.49Kb Microsoft Excel View/Open MAC_Silicon
MAC_15_P.csv 6.080Kb Microsoft Excel View/Open MAC_Phosphorous
MAC_16_S.csv 5.948Kb Microsoft Excel View/Open MAC_Sulphur
MAC_17_Cl.csv 13.71Kb Microsoft Excel View/Open MAC_Chlorine
MAC_19_K.csv 5.959Kb Microsoft Excel View/Open MAC_Potassium
MAC_20_Ca.csv 5.979Kb Microsoft Excel View/Open MAC_Calcium
MAC_21_Sc.csv 6.000Kb Microsoft Excel View/Open MAC_Scandium
MAC_22_Ti.csv 7.005Kb Microsoft Excel View/Open MAC_Titanium
MAC_23_V.csv 5.955Kb Microsoft Excel View/Open MAC_Vanadium
MAC_24_Cr.csv 6.016Kb Microsoft Excel View/Open MAC_Chromium
MAC_25_Mn.csv 6.016Kb Microsoft Excel View/Open MAC_Manganese
MAC_26_Fe.csv 5.982Kb Microsoft Excel View/Open MAC_Iron
MAC_27_Co.csv 5.914Kb Microsoft Excel View/Open MAC_Cobalt
MAC_28_Ni.csv 5.925Kb Microsoft Excel View/Open MAC_Nickel
MAC_29_Cu.csv 5.918Kb Microsoft Excel View/Open MAC_Copper
MAC_30_Zn.csv 5.911Kb Microsoft Excel View/Open MAC_Zinc
MAC_37_Rb.csv 986bytes Microsoft Excel View/Open MAC_Rubidium
MAC_38_Sr.csv 1.006Kb Microsoft Excel View/Open MAC_Strontium
MAC_56_Ba.csv 1.907Kb Microsoft Excel View/Open MAC_Barium
Heirwegh_Christopher_201404_PhD.pdf 4.774Mb PDF View/Open Dissertation_pdf

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