MODELING OF THE MAPPING EXPERIMENTS BASED ON THE DIFFUSION PROCESS

It is important in relation to the plasma confinement to understand th e spatial variation of the impedance observed by the ''stellarator dio de method''. We develop a numerical code based on the collisional diff usion model and apply it to the various experimental conditions. It is shown that the ripple diffusion of electrons plays an important role in determination of the impedance between a magnetic surface and the v acuum vessel wall. The effects of the electron temperature, neutral pr essure, helical ripple, and the magnetic island are also examined.