Improvement of photon transport model by including coupled photon-electron transport and kernel refinement

Di Giulio, Eugenio (2015) Improvement of photon transport model by including coupled photon-electron transport and kernel refinement, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Ingegneria energetica, nucleare e del controllo ambientale, 27 Ciclo. DOI 10.6092/unibo/amsdottorato/6954.
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The first part of this work deals with the inverse problem solution in the X-ray spectroscopy field. An original strategy to solve the inverse problem by using the maximum entropy principle is illustrated. It is built the code UMESTRAT, to apply the described strategy in a semiautomatic way. The application of UMESTRAT is shown with a computational example. The second part of this work deals with the improvement of the X-ray Boltzmann model, by studying two radiative interactions neglected in the current photon models. Firstly it is studied the characteristic line emission due to Compton ionization. It is developed a strategy that allows the evaluation of this contribution for the shells K, L and M of all elements with Z from 11 to 92. It is evaluated the single shell Compton/photoelectric ratio as a function of the primary photon energy. It is derived the energy values at which the Compton interaction becomes the prevailing process to produce ionization for the considered shells. Finally it is introduced a new kernel for the XRF from Compton ionization. In a second place it is characterized the bremsstrahlung radiative contribution due the secondary electrons. The bremsstrahlung radiation is characterized in terms of space, angle and energy, for all elements whit Z=1-92 in the energy range 1–150 keV by using the Monte Carlo code PENELOPE. It is demonstrated that bremsstrahlung radiative contribution can be well approximated with an isotropic point photon source. It is created a data library comprising the energetic distributions of bremsstrahlung. It is developed a new bremsstrahlung kernel which allows the introduction of this contribution in the modified Boltzmann equation. An example of application to the simulation of a synchrotron experiment is shown.

Tipologia del documento
Tesi di dottorato
Di Giulio, Eugenio
Dottorato di ricerca
Scuola di dottorato
Ingegneria industriale
Settore disciplinare
Settore concorsuale
Parole chiave
Inverse problem solution, Maximum etropy technique, Detector response function, X-ray Boltzman equation, Single shell Compton cross section, photon-electron transport problem, Monte Carlo simuation, Bremsstrahlung radiative emission, Interaction kernel
Data di discussione
29 Aprile 2015

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