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Transport of magnetic field lines and particles in tokamaks and plasma modeling for deposition and etching


Transport barriers of the magnetic field lines have an important role in the controlled fusion in tokamaks. Through the devices that cause external perturbations, which can be an ergodic magnetic limiter, which perturbs rational surfaces at the edge of the plasma column, it is possible to form a layer with chaotic lines in this region. With non-monotonic safety factor profile we have the chaotic layer forming an internal transport barrier, which prevents the transport of the field lines. Through a Hamiltonian formulation, the escape of the field lines toward the walls of the tokamak was investigated using a ergodic magntic limiter to produce resonant perturbations. Transport barriers called toro robust and labyrinthine barriers, which may influence the transport of magnetic field lines toward the walls of the tokamak were also investigated. Several studies have been made to the study of tokamaks with poloidal divertors, since the purpose of a divertor is to redirect the plasma escape toward the separatrix. We built a model to study tokamaks with divertor using a conservative map for MHD equilibrium, which presents an X point, following the methodology described by Morrison Abbamonte. The advantage of this map lies in the fact that we can choose a profile of safety factor related to a realistic magnetic configuration. We apply this methodology for circular section tokamaks including resonant perturbations. Besides, we investigated the transport of magnetic field lines with elongated cross section. It is proposed to continue this work using the proposed model with profiles of safety factor as provided for ITER tokamak. We study the effects of such profiles on the transport phenomena. This will be studied in collaboration with Dr. Todd E. Evans of General Atomics,USA. It is also proposed to study the turbulence caused by waves drift in plasmas fusion. It will be made a numerical model which will mimic the waves that arise from drift due to nonuniformity of the plasma by electrostatic magnetic confinement. The anomalous transport of particles observed on the edge of tokamaks generated by the fluctuation of the electric potential of the plasma may degrade the plasma confinement according to fluctuation amplitude. This transport also depends on the nonuniformity of the electric and magnetic fields.Besides, it is proposed to investigate the particle transport in tokamaks through computer simulation using the code Cronos. It is proposed to investigate the equilibrium MHD using a toroidal inverted current profile with the code Cronos. Was also studied an analytical solution of the Grad-Shafranov equation with negative toroidal current which produces magnetic islands near the magnetic axis. We investigated the influence of these islands on transport phenomena.In addition it is proposed to study the modeling of low pressure plasma discharge using radio-frequency capacitive and inductive reactors. We simulate these discharges using a PIC/MCC model and a global model. (AU)

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Scientific publications (5)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
TONELI, D. A.; PESSOA, R. S.; ROBERTO, M.; GUDMUNDSSON, J. T.. On the formation and annihilation of the singlet molecular metastables in an oxygen discharge. JOURNAL OF PHYSICS D-APPLIED PHYSICS, v. 48, n. 32, . (13/03401-6)
MARTINS, CAROLINE G. L.; ROBERTO, MARISA; CALDAS, IBERE L.. Magnetic Field Line Stickiness in Tokamaks. IEEE TRANSACTIONS ON PLASMA SCIENCE, v. 42, n. 10, 1, SI, p. 2764-2765, . (13/03401-6, 10/13162-0)
ROSALEM, K. C.; ROBERTO, M.; CALDAS, I. L.. Influence of the electric and magnetic shears on tokamak transport. NUCLEAR FUSION, v. 54, n. 6, . (13/03401-6, 11/19296-1)
TONELI, D. A.; PESSOA, R. S.; ROBERTO, M.; GUDMUNDSSON, J. T.. A volume averaged global model study of the influence of the electron energy distribution and the wall material on an oxygen discharge. JOURNAL OF PHYSICS D-APPLIED PHYSICS, v. 48, n. 49, . (13/03401-6)
MARTINS, CAROLINE G. L.; ROBERTO, M.; CALDAS, I. L.. Delineating the magnetic field line escape pattern and stickiness in a poloidally diverted tokamak. Physics of Plasmas, v. 21, n. 8, . (13/03401-6, 10/13162-0)

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