Plasma diffusion across magnetic field

Early experience also showed that the induced plasma current in a tokamak generates a magnetic field that loops die minor axis nf Ihe torus. The field lines form helices along the toroidal surface the plasma must cross the lines to escape. It does so through the cumulative action of many random displacements caused by interparticle collisions, tin effect diffusing across the field lines and out of the system). Thermal energy is transported by much the same process. 

FIGURE10 The pattern of plasma drift at low latitudes due to the combined action of an electromagnetic drift across magnetic field lines and plasma diffusion along field lines. The magnetic field lines are shown every 200 km above the equator. [From Hanson, W. B., and Moffett, R. J. (1966). J. Geophys. Res. 71, 5559.]... 

Particle confinement. Particles escape from the trap both directly through the slits and along the plasma sheath whose width hs is determined by the balance between particle escape from the sheath and diffusion across the magnetic field. Reference /6/ shows the calculation for hs 0.3 rm in the laminar case. The account of both mechanisms of particle escape leads to an effective size of the slit h < Tht llj. The upper limit h Thi is used below. 

---