We would like to thank Professor Tiago Fiorini da Silva for suggesting the project, his help on the modeling of the detector e ects and response function (see Chapter 4), his e orts on measuring the PIXE spectra at LAMFI (see Chapter 5), and his assistance on the interpretations of such data.We would like to thank Professor José Maria Fernández-Varea for providing the numerical DHFS wave functions and the velocity distributions employed in this work (see Chapter 5). We are also in debt for his help in understanding the theoretical results and for his important contributions to both the published article and the poster presented at the IBA2019 Conference.The present work has been supported by Conselho Nacional de Desenvolvimento Cientíco e Tecnológico (CNPq) with the Ph.D. fellowship number 141193/2016-6.Aos meus pais.

ResumoAtravés de um mapa de ondas de deriva, estudamos o transporte de partículas no Texas Helimak, considerando diversos perfis do campo elétrico radial. O Texas Helimak é um equipamento de confinamento magnético caracterizado por linhas de campo helicoidais e que fornece uma aproximação experimental de um plasma unidimensional. Ele possibilita a imposição de um potencial elétrico externo ao plasma, chamado bias, que altera o perfil radial do campo elétrico de equilíbrio e, consequentemente, possui influência sobre as características de transporte no plasma. Para estudar o efeito do bias sobre o transporte, utilizamos um modelo que considera flutuações eletrostáticas, associadas à deriva ⃗ × ⃗ , como mecanismo de turbulência. Com isso, introduzimos um mapa de ondas de deriva, cujos parâmetros estão relacionados a dados experimentais para diversos valores de bias.Assim, ao variar o bias, pudemos observar a formação e a destruição da curva sem shear, bem como seu efeito sobre o transporte das trajetórias no espaço de fase. AbstractUsing a drift wave map, we studied the particle transport in Texas Helimak considering various electric field radial profiles. Texas Helimak is a device for magnetic confinement characterized by helical field lines, and constitutes an experimental approximation to a one-dimensional plasma. It allows for the imposing of an external electric potential, known as bias, which changes the equilibrium electric field radial profile and hence the transport properties of the plasma. In order to study the effects of the bias potential on the particle transport, we used a model with electrostatic fluctuations associated to ⃗ × ⃗ drift as the turbulence mechanism. Thus, we introduced a drift wave map whose parameters are related to experimental data for various values of bias. Therefore, by varying the bias, we observed the formation and destruction of the shearless curve, as well as its effects on trajectories transport in the map's phase space. Lista de Figuras