Cesar Gutierrez-Tapia

arXiv2004

Electron cyclotron current drive efficiency in an axisymmetric tokamak

The neoclassical transport theory is applied to calculate electron cyclotron current drive (ECCD) efficiency in an axisymmetric tokamak in the low-collisionality regime. The tokamak ordering is used to obtain a system of equations that describe the dynamics of the plasma where the nonlinear ponderomotive (PM) force due to high-power RF waves is included. The PM force is produced around an electron cyclotron resonant surface at a specific poloidal location. The ECCD efficiency is analyzed in the cases of first and second harmonics (for different impinging angles of the RF waves) and it is validated using experimental parameter values from TCV and T-10 tokamaks. The results are in agreement with those obtained by means of Green's function techniques.

physics.plasm-ph↗

arXiv2004

A comparative analysis of the EEDF obtained by regularization methods and by a least-squares fitting

To establish the electron energy distribution function (EEDF), the second derivative of a Langmuir probe current-voltage (I-V) characteristic is numerically integrated using the Tikhonov singular value decomposition regularized method. A comparison of the numerically intagrated EDDF and by a least-squares fitting is discussed. The used I-V haracteristic is measured in an ECR plasma source using a cylindrical probe and the plasma parameters are determined by the Laframboise theory. This technique allows a rapid analysis of plasma parameters at any gas pressure. The obtained EEDF, for the case of the ECR plasma source, shows the existence of two groups of electrons with different temperatures. This result is associated with the collisional mechanism heating taking place in ECR plasma sources, where low pressure plasma is sustained by electron impact ionization of the ground state molecules or atoms by energetic electrons arising in the resonance zone.

physics.plasm-ph↗