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<p>High-precision differential cross section data of the neutron-deuteron elastic scattering reaction at 95 MeV are presented. The neutron-proton scattering differential cross section was also measured and used as a reference to allow an accurate absolute normalization of the neutron-deuteron data.</p><p>Two multi-detector arrays were used, MEDLEY and SCANDAL, at the neutron beam facility at The Svedberg Laboratory in Uppsala. Three different configurations of the detectors allowed to perform three independent measurements. The first experiment involved detecting recoil deuterons from thin deuterated polyethylene targets with the MEDLEY setup and allowed a large angular coverage. In the second experiment, high-precision data were obtained at neutron backward angles, using the SCANDAL setup with the same technique. For the third experiment, data were obtained in the forward angular range using the SCANDAL setup with a technique where neutrons scattered on heavy water were detected by neutron-proton conversion in plastic scintillators and tracking the protons through the detectors. Events from elastic neutron-deuteron scattering were identified in the data analysis, and differential cross sections were obtained after applying corrections and evaluating systematic uncertainties due to effects which could affect the shape or the absolute normalization of the data.</p><p>The results are compared with modern Faddeev calculations using realistic nucleon-nucleon potentials combined with three-nucleon interactions. The effects of three-nucleon forces are expected to increase the differential cross section by about 30% in the region of the minimum. The data agree with this prediction, thus providing evidence for three-nucleon force effects.</p>

High-precision differential cross section data of the neutron-deuteron elastic scattering reaction at 95 MeV are presented. The neutron-proton scattering differential cross section was also measured and used as a reference to allow an accurate absolute normalization of the neutron-deuteron data. Two multi-detector arrays were used, MEDLEY and SCANDAL, at the neutron beam facility at The Svedberg Laboratory in Uppsala. Three different configurations of the detectors allowed to perform three independent measurements. The first experiment involved detecting recoil deuterons from thin deuterated polyethylene targets with the MEDLEY setup and allowed a large angular coverage. In the second experiment, high-precision data were obtained at neutron backward angles, using the SCANDAL setup with the same technique. For the third experiment, data were obtained in the forward angular range using the SCANDAL setup with a technique where neutrons scattered on heavy water were detected by neutron-proton conversion in plastic scintillators and tracking the protons through the detectors. Events from elastic neutron-deuteron scattering were identified in the data analysis, and differential cross sections were obtained after applying corrections and evaluating systematic uncertainties due to effects which could affect the shape or the absolute normalization of the data. The results are compared with modern Faddeev calculations using realistic nucleon-nucleon potentials combined with three-nucleon interactions. The effects of three-nucleon forces are expected to increase the differential cross section by about 30% in the region of the minimum. The data agree with this prediction, thus providing evidence for three-nucleon force effects.

A Field Programmable Gate Array (FPGA)-based Polymorphic Faddeev Systolic Array (PolyFSA) architecture is proposed to accelerate an Extended Kalman Filter (EKF) algorithm. A system architecture comprising a software processor as the host processor, a hardware controller, a cache-based memory sub-system, and the proposed PolyFSA as co-processor, is presented. PolyFSA-based system architecture is implemented on a Xilinx Virtex 4 family of FPGAs. Results indicate significant speed-ups for the proposed architecture when compared against a space-based software processor. This dissertation proposes a comprehensive architecture analysis that is comprised of (i) error analysis, (ii) performance analysis, and (iii) area analysis. Results are presented in the form of 2-D pareto plots (area versus error, area versus time) and a 3-D plot (area versus time versus error). These plots indicate area savings obtained by varying any design constraints for the PolyFSA architecture. The proposed performance model can be reused to estimate the execution time of EKF on other conventional hardware architectures. In this dissertation, the performance of the proposed PolyFSA is compared against the performance of two conventional hardware architectures. The proposed architecture outperforms the other two in most test cases.

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Cette thèse est consacrée au calcul de sections efficaces de réactions impliquant le système à trois corps (e − , e + , p̄) à des énergies représentatives de l’expérience GBAR. Deux approches théoriques ont été utilisées. La première, appelée méthode des canaux couplés, permet de traiter le système dans un cadre théorique plus simple. La deuxième, basée sur le formalisme rigoureux des équations de Faddeev-Merkuriev, a permis le calcul explicite des sections efficaces. Une des difficultés majeures provient de la dégénérescence accidentelle du premier état excité des atomes d’antihydrogène et de positronium. Le traitement de cette dégénérescence a été réalisé dans un premier temps dans le formalisme de canaux couplés avant d’être adapté au code des équations de Faddeev-Merkuriev. Dans ce document, nous discutons les sections efficaces dans le contexte de l’expérience GBAR et interprétons les phénomènes résonnants mis en évidence, les résonances de Feshbach et les oscillations de Gailitis-Damburg. / This thesis is dedicated to cross section calculations involving the three body system (e − , e + , p̄) at representative energies for the GBAR experiment. Two different theoretical formalisms have been used. The first one, the close coupling method, allows to study the system in a more simple and schematic theoretical frame. The second, based on the mathematically rigorous formalism of the Faddeev-Merkuriev equations, is used to compute the explicit cross sections. One of the major difficulties comes from the accidental degeneracy of the antihydrogen and positronium atoms first excited states. The treatment of this degeneracy has been realised, in a first time, with the close-coupling formalism before being adapted to the Faddeev-Merquriev equations code. In this document, we discuss the cross sections in the GBAR experiment frame and we construe the highlighted resonant phenomena, the Feshbach resonances and the Gailitis-Damburg oscillations.

Bound state systems consisting of three nonrelativistic particles are numerically studied. Calculations are performed employing two-body and three-body forces as input in the Hamiltonian in order to study the role or contribution of three-body forces to the binding in these systems. The resulting differential Faddeev equations are solved as three-dimensional equations in the two Jacobi coordinates and the angle between them, as opposed to the usual partial wave expansion approach. By expanding the wave function as a sum of the products of spline functions in each of the three coordinates, and using the orthogonal collocation procedure, the equations are transformed into an eigenvalue problem. The matrices in the aforementioned eigenvalue equations are generally of large order. In order to solve these matrix equations with modest and optimal computer memory and storage, we employ the iterative Restarted Arnoldi Algorithm in conjunction with the so-called tensor trick method. Furthermore, we incorporate a polynomial accelerator in the algorithm to obtain rapid convergence. We applied the method to obtain the binding energies of Triton, Carbon-12, and Ozone molecule. / Physics / M.Sc (Physics)

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Bound state systems consisting of three nonrelativistic particles are numerically studied. Calculations are performed employing two-body and three-body forces as input in the Hamiltonian in order to study the role or contribution of three-body forces to the binding in these systems. The resulting differential Faddeev equations are solved as three-dimensional equations in the two Jacobi coordinates and the angle between them, as opposed to the usual partial wave expansion approach. By expanding the wave function as a sum of the products of spline functions in each of the three coordinates, and using the orthogonal collocation procedure, the equations are transformed into an eigenvalue problem. The matrices in the aforementioned eigenvalue equations are generally of large order. In order to solve these matrix equations with modest and optimal computer memory and storage, we employ the iterative Restarted Arnoldi Algorithm in conjunction with the so-called tensor trick method. Furthermore, we incorporate a polynomial accelerator in the algorithm to obtain rapid convergence. We applied the method to obtain the binding energies of Triton, Carbon-12, and Ozone molecule. / Physics / M.Sc (Physics)