Sumários
Tokamak 3
3 dezembro 2019, 17:00 • Paulo Rodrigues
Stability assessment using the simplified surface-current model: Harmonic-type solution for the perturbations, poloidal and toroidal mode numbers; Matching at the plasma-vacuum interface; The eigenvalue problem written in terms of the safety factor q, poloidal and toroidal mode numbers; The stability condition q>1 and Kruskal-Shafranov stability limit for the plasma current.
Tokamak 2
28 novembro 2019, 16:00 • Paulo Rodrigues
The equilibrium poloidal field as a series approximation in the inverse aspect ratio; Relation with the plasma beta, safety factor, and plasma current; The equilibrium beta limit at constant plasma current.
Tokamak 1
26 novembro 2019, 17:00 • Paulo Rodrigues
The tokamak among several magnetic confinement alternatives: advantages and drawbacks; operation and typical profiles;inverse aspect ratio ordering and expansion. Description of the magnetic field by a simplified surface-current model: Background equilibrium and perturbations; Matching conditions at the plasma-vacuum interface and reduction to an eigenvalue problem.
Alfven waves.
21 novembro 2019, 16:00 • Paulo Rodrigues
Waves in electrically conductive fluids: Governing equations and physical picture; Fluid displacement, induced fields, and restoring forces; The role of inertia and field-line tension; Alfven velocity. Alfven waves in homogeneous plasmas: Dispersion relation and characteristic velocities (Alfven and sound); The three propagation branches (shear, slow magnetosonic, fast magnetosonic) and dominant polarisations; The role of plasma beta. Very brief and qualitative introduction to Alfven waves in non-homogeneous plasmas: radial dependence of the frequency, phase mixing, and resonant absorption.
MHD stability 3
19 novembro 2019, 17:00 • Paulo Rodrigues
Stability of 1-d magnetic configurations: the z-pinch and the theta-pinch; the unconditional stability of the theta-pinch; a simplified approach to the energy principle and its generalisation to include the magnetic curvature; the limiting effect of the pressure gradient in the z-pinch stability.