The M-shell x-ray production cross section for thorium and uranium have been determined for protons of energy 0.4 - 4.0 MeV, helium ions of energy 0.4 - 6.0 MeV, carbon ions of energy 4.5 - 11.3 MeV and oxygen ions of energy 4.5 - 13.5 MeV. The total cross sections and the cross sections for individual x-ray peaks in the spectrum, consisting of the following transitions Mz (M4-N2, M5-N3, M4-N3), Ma (M5-N6,7), Mb (M4-N6, M5-O3, M4- O2), and Mg (M4-O3, M5-P3, M3-N4, M3-N5), were compared to the theoretical values determined from the PWBA + OBKN and ECUSAR. The theoretical values for the carbon and oxygen ions were also modified to take into account the effects of multiple ionizations of the target atom by the heavier ions. It is shown that the results of the ECUSAR theory tend to provide better agreement with the experimental data.

L- and M-shell x-ray production cross sections have been measured for thin solid targets of neodymium, gadolinium, holmium, ytterbium, gold, and lead by 25 MeV 12/6C^q+ (q=4,5,6) and by 32 MeV 16/8O^q+ (q=5,7,8). The cross sections were determined from measurements made with thin targets (< 2.5 μg/cm2). For projectiles with one or two K-shell vacancies, the target x-ray production cross sections were found to be enhanced over those for projectiles without a K-shell vacancy. The sum of direct ionization to the continuum (DI) plus electron capture (EC) to the L, M, N... shells and EC to the K-shell of the projectile have been extracted from the data. The results are compared to the predictions of first Born theories, i.e., plane wave Born approximation for DI and Oppenheimer-Brinkman-Kramers formula of Nikolaev for EC and to the ECPSSR approach that accounts for Energy loss and Coulomb deflection of the projectile as well as for Relativistic and Perturbed Stationary States of inner shell electrons.

The charge state dependence of M-shell x-ray production cross sections of 67HO bombarded by 2-12 MeV carbon ions with and without K-vacancies are reported. The experiment was performed using an NEC 9SDH-2 tandem accelerator at the Ion Beam Modification and Analysis Laboratory of the University of North Texas. The high charge state carbon ions were produced by a post-accelerator stripping gas cell. Ultra-clean holmium targets were used in ion-atom collision to generate M-shell x rays at energies from 1.05 to 1.58 keV. The x-ray measurements were made with a windowless Si(Li) x-ray detector that was calibrated using radiative sources, particle induced x-ray emission (PIXE), and the atomic field bremsstrahlung (AFB) techniques.

Incident 0.5 to 2.5 MeV charged particle beams were used to ionize the inner-shells of selected targets and study their subsequent emission of characteristic x-rays. ⁹Be⁺ ions were used to examine K-shell x-ray production from thin F, Na, Al, Si, P, Cl, and K targets, L-shell x-ray production from thin Cu, An, Ge, Br, Zr and Ag targets, and M-shell x-ray production from thin Pr, Nd, Eu, Dy, Ho, Hf, W, Au, Pb and Bi targets. L-shell x-ray production cross sections were also measured for ²⁷Al⁺ ions incident upon Ni, Cu, Zn, As, Zr, and Pd targets. M-shell x-ray production cross sections were measure for ²⁷Al⁺ and ⁴⁰Ar⁺ ions incident upon Pr, Nd, Gd, Dy, Lu, Hf, Au, Pb, Bi, and U targets. These measurements were performed using the 2.5 MV Van de Graaff accelerator at North Texas State University. The x-rays were detected with a Si(Li) detector whose efficiency was determined by fitting a theoretical photon absorption curve to experimentally measure values. The x-ray yields were normalized to the simultaneously measured Rutherford backscattered (RBS) yields which resulted in an x-ray production cross section per incident ion. The RBS spectrum was obtained using a standard surface barrier detector calibrated for to account for the "pulse height defect." The experimental results are compared to the predictions of both the first Born and ECPSSR theories; each of which is composed of two parts, the direct ionization (DI) of the target electron to the continuum and the capture (EC) of the target electron to the projectile. The first Born describes DI by the Plane-Wave-Born-Approximation (PWBA) and EC by the Oppenheimer-Brinkman-Kramers treatment of Nikolaev (OBKN). ECPSSR expands upon the first Born by using perturbed (PSS) and relativistic (R) target electron wave functions in addition to considering the energy loss (E) of the projectile in the target and its deviation from straight line trajectory (Coulomb deflection (C)). The measurements presented show that the first Born theories overestimate the measured results rather significantly for all experiments using the ⁹Be beams to examine the inner shell x-rays, while the ECPSSR predictions fir the measured data much better. For incident ²⁷Al and ⁴⁰Ar ions, the measured results are not predicted by the theories. The first Born generally over-predicts the data for low target atomic numbers while under-predicting at high atomic numbers. The ECPSSR theory greatly under-predicts the results (factors of 10³ to 10²⁰). Reasons for this behavior are discussed as well as suggestions for future experiments.

Incident ¹H⁺ and ⁴He⁺ ions at 0.3-2.6 MeV and ¹⁹F^q⁺ ions at 25, 27 and 35 MeV were used to study the M-shell x-ray production cross sections of Au, Pb, Bi and U. For the incident fluorine ions, projectile charge state dependence of the cross sections were extracted from measurements made with varying target thicknesses ( ~1 to ~300 μg/cm²). The efficiency of the Si(Li) detector was determined by measuring the K-shell x-ray production of various low Z elements and comparing these values to the prediction of the CPSS theory. The experimental results are compared to the prediction of first Born approximation for direct ionization to the continuum and to the OBK of Nikolaev for the electron capture to the K-, L-, M-...shells of the incident ion. Comparison is also made with the ECPSSR theory that accounts for the energy loss, Coulomb deflection, and relativistic effects in the perturbed stationary state theory.

L-shell x-ray production cross sections have been measured for thin targets of 29Cu, 32Ge, 37Rb, 38Sr, and 39Y. M-shell x-ray production cross sections have been measured for thin targets of 79Au, 82Pb, 83Bi, 90Th, and 92U. All targets were irradiated with a beam of H+ ions with energies in a range from 70 to 200 keV. Experimental cross sections are compared to other measurements at higher energies and to first Born (Plane Wave Born Approximation for direct ionization and Oppenheimer-Brinkman-Kramers-Nikolaev approximation for electron capture) and the ECPSSR (Energy loss, Coulomb deflection, Perturbed Stationary State calculations with Relativistic effects) theoretical cross sections.

Characteristic L-shell x rays of the five rare earths Pr, Sm, Eu, Gd, and Dy were studied in this work. The x rays were produced by ionization from 0.3 to 2.0 MeV protons from the 2.0 MV Van de Graaff at North Texas State University. Total L-shell ionization and x-ray production cross sections were measured for Sm and compared to the BEA, CBEA and PWBA theories. Total L-shell ionization cross sections were measured for Pr, Eu, Gd, and Dy and compared to the BEA, CBEA, and PWBA. The CBEA and PWBA fit the samarium data well for both ionization and x-ray production cross sections. The BEA was generally 40 per cent lower than the data. The CBEA and the PWBA also fit the ionization cross section data for Pr, Eu, Gd and Dy, while the BEA was generally 40 per cent lower than the data.

Este trabalho teve como objetivo validar uma ferramenta computacional para a realização de simulações da interação de elétrons e da radiação X com a matéria, utilizando o método de Monte Carlo para possíveis estudos em radiologia diagnóstica. Para esse propósito, foi desenvolvido um programa computacional que simula a produção de radiação de um equipamento de raios X, com a finalidade de obter a distribuição de energia dos fótons que alcançam uma determinada região de interesse, sem a necessidade de medições experimentais. Outra tarefa realizada neste trabalho foi o cálculo da resposta de um detector do tipo CdTe, para possibilitar a correção de espectros medidos com esse detector em experimentos na faixa de energia de radiodiagnóstico. A ferramenta computacional escolhida para essas aplicações foi o Geant4, que é um conjunto de programas de distribuição livre relativamente novo e que é utilizado para simulações da interação da radiação com a matéria. Um dos principais diferenciais do Geant4 é o emprego da tecnologia de programação orientada a objetos e de técnicas avançadas de engenharia de software. Os resultados da etapa de simulação de espectros de energia produzidos por um equipamento de raios X mostram que o Geant4 pode ser utilizado para esta aplicação, mas com ressalvas na simulação de espectros de raios X com alvos com molibdênio para a região de mamografia, que é a situação onde as diferenças dos rendimentos de raios X característicos dos espectros simulados com os seus respectivos espectros de referência são maiores. Na etapa de simulação da detecção da radiação X por um detector do tipo CdTe são apresentados resultados com excelente acordo com os dados de referência. As diferenças encontradas devem ser mais influenciadas pelos efeitos de armadilhamento de cargas e do comportamento do campo elétrico no interior do cristal do detector, que são específicos para este detector e não fazem parte dos modelos físicos fornecidos pelo Geant4. Desta forma, a validação do Geant4 realizada neste trabalho mostrou algumas das possibilidades de uso desta versátil ferramenta na área de radiologia diagóstica. / The aim of this work was the validation of a computational tool applied in simulations of electrons and X ray interactions with matter, using the Monte Carlo method for possible studies in diagnostic radiology. To perform this task, a computational program was developed to simulate the radiation production of a X ray equipment, with the purpose of obtaining the photon energy distribution which comprehends the region of interest, without the necessity of experimental measurements. Another task carried through in this work was the calculation of a CdTe detector response, which was used in the correction of measured spectra with energy distribution typically found in diagnostic radiology. The employed computational tool was Geant4, which is a free distribution set of computational programs used for simulation of the passage of particles through matter. One of the main differentials of Geant4 is the exploitation of advanced software-engineering techniques and object-oriented technology. The results of the simulation of energy spectra produced by a X ray equipment show that Geant4 can be used for this application, but with restrictions concerning the simulation of X ray spectra from molybdenum targets in the mammography energy range. This is the situation where the differences of the characteristic X ray yield between the simulated and reference spectra are more pronounced. For the simulation of X ray measurements with a CdTe detector, the results showed excellent agreement with the reference data. In this case the discrepancies must be originated mainly by effects of charge trapping and the nonuniformity of the electric field inside the CdTe crystal. In resume, the validation of the Geant4 carried through in this work showed some of the possibilities for the use of this versatile tool in diagnostic radiology.

The purpose of this work was to examine the effect of the use the assumption κω2K/ΕCM «1 in calculating K-shell ionization cross sections in the plane wave Born approximation (PWBA) where κω2K is the observed binding energy of the K-shell and ECM is the energy of the incident particle in the center of mass system. Avoiding this assumption produces a threshold for ionization at Ecm = κω2K. Calculations employing the assumption, which leads to the use of approximate limits of integration, do not go to zero for even the .Lowest values of the incident energy.

Este trabalho teve como objetivo validar uma ferramenta computacional para a realização de simulações da interação de elétrons e da radiação X com a matéria, utilizando o método de Monte Carlo para possíveis estudos em radiologia diagnóstica. Para esse propósito, foi desenvolvido um programa computacional que simula a produção de radiação de um equipamento de raios X, com a finalidade de obter a distribuição de energia dos fótons que alcançam uma determinada região de interesse, sem a necessidade de medições experimentais. Outra tarefa realizada neste trabalho foi o cálculo da resposta de um detector do tipo CdTe, para possibilitar a correção de espectros medidos com esse detector em experimentos na faixa de energia de radiodiagnóstico. A ferramenta computacional escolhida para essas aplicações foi o Geant4, que é um conjunto de programas de distribuição livre relativamente novo e que é utilizado para simulações da interação da radiação com a matéria. Um dos principais diferenciais do Geant4 é o emprego da tecnologia de programação orientada a objetos e de técnicas avançadas de engenharia de software. Os resultados da etapa de simulação de espectros de energia produzidos por um equipamento de raios X mostram que o Geant4 pode ser utilizado para esta aplicação, mas com ressalvas na simulação de espectros de raios X com alvos com molibdênio para a região de mamografia, que é a situação onde as diferenças dos rendimentos de raios X característicos dos espectros simulados com os seus respectivos espectros de referência são maiores. Na etapa de simulação da detecção da radiação X por um detector do tipo CdTe são apresentados resultados com excelente acordo com os dados de referência. As diferenças encontradas devem ser mais influenciadas pelos efeitos de armadilhamento de cargas e do comportamento do campo elétrico no interior do cristal do detector, que são específicos para este detector e não fazem parte dos modelos físicos fornecidos pelo Geant4. Desta forma, a validação do Geant4 realizada neste trabalho mostrou algumas das possibilidades de uso desta versátil ferramenta na área de radiologia diagóstica. / The aim of this work was the validation of a computational tool applied in simulations of electrons and X ray interactions with matter, using the Monte Carlo method for possible studies in diagnostic radiology. To perform this task, a computational program was developed to simulate the radiation production of a X ray equipment, with the purpose of obtaining the photon energy distribution which comprehends the region of interest, without the necessity of experimental measurements. Another task carried through in this work was the calculation of a CdTe detector response, which was used in the correction of measured spectra with energy distribution typically found in diagnostic radiology. The employed computational tool was Geant4, which is a free distribution set of computational programs used for simulation of the passage of particles through matter. One of the main differentials of Geant4 is the exploitation of advanced software-engineering techniques and object-oriented technology. The results of the simulation of energy spectra produced by a X ray equipment show that Geant4 can be used for this application, but with restrictions concerning the simulation of X ray spectra from molybdenum targets in the mammography energy range. This is the situation where the differences of the characteristic X ray yield between the simulated and reference spectra are more pronounced. For the simulation of X ray measurements with a CdTe detector, the results showed excellent agreement with the reference data. In this case the discrepancies must be originated mainly by effects of charge trapping and the nonuniformity of the electric field inside the CdTe crystal. In resume, the validation of the Geant4 carried through in this work showed some of the possibilities for the use of this versatile tool in diagnostic radiology.