Pinch Effect for Trapped Particles in a Tokamak

Abstract

Conservation of canonical angular momentum is shown to require that all trapped particles drift towards the magnetic axis with velocity $\frac{c{E}_{\ensuremath{\phi}}}{{B}_{\ensuremath{\theta}}}$ (${E}_{\ensuremath{\phi}}$ is the toroidal electric field; ${B}_{\ensuremath{\theta}}$ the poloidal magnetic field). This property, plus an amplification process for the number of trapped particles, will explain the relaxation oscillations which occur for $q<3$. In addition, there is experimental evidence that it is an important contribution to the good containment when $q>3$.