Browsing by Author "Correia, Pedro M. M."

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    A dynamic method for charging-up calculations: The case of GEM
    (IOP Publishing, 2014-06-26) Correia, Pedro M. M.; Oliveira, Carlos A. B.; Azevedo, C. D. R.; Silva, Ana Luísa M.; Nemallapudi, Mythra Varun; Veloso, J. F. C. A.; Veenhof, Robert J.; Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Bölümü.; 6603742499
    The simulation of Micro Pattern Gaseous Detectors (MPGDs) signal response is an important and powerful tool for the design and optimization of such detectors. However, several attempts to exactly simulate the effective gas gain have not been completely successful. Namely, the gain stability over time has not been fully understood. Charging-up of the insulator surfaces have been pointed as one of the responsible for the difference between experimental and Monte Carlo results. This work describes two iterative methods to simulate the charging-up in one MPGD device, the Gas Electron Multiplier (GEM). The first method, which uses a constant step size for avalanches time evolution, is very detailed but slow to compute. The second method instead uses a dynamic step-size that improves the computing time. Good agreement between both methods was achieved. Comparison with experimental results shows that charging-up plays an important role in detectors operation, explaining the time evolution of the gain. However it doesn't seem to be the only responsible for the difference between measurements and Monte Carlo simulations.
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    Pressure effects on the X-ray intrinsic position resolution in noble gases and mixtures
    (IOP Publishing, 2016-12-02) Azevedo, Carlos D. R.; Gonzalez -Diaz, Diego; Correia, Pedro M. M.; Silva, Ana L. M.; Carramate, Lara F. N. D.; Veloso, Joao F. C. A.; Biagi, Stephen; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 57193398882
    A study of the effect of gas pressure in the position resolution of an interacting X or gamma-ray photon in a gas medium is performed. The intrinsic position resolution for pure noble gases (Argon and Xenon) and their mixtures with CO2 and CH4 was calculated for several gas pressures (1-10 bar) and for photon energies between 1 and 60 keV, being possible to establish a linear relation between the intrinsic position resolution and the inverse of the gas pressure in the indicated energy range, as intuitively expected. We show how, at high pressures and low photoelectron energies, this intrinsic 1/P scaling is modified due to the diffusion of the primary ionization in the direction perpendicular to the electric field. In order to evaluate the quality of the method here described, a comparison between the available experimental data and microscopic simulations is presented in this work and discussed. In the majority of cases, a good agreement is observed. The conditions to achieve position resolutions down to 10 mu m in a realistic detector are shown and discussed.