One-dimensional modeling of transport in small stellarators

An existing stellarator reactor transport code was modified to model small stellarator experiments. Changes were made in the treatment of neutrals, the atomic physics process, and the transport models. The authors investigated the extent to which the hollow density profiles experimentally detected during electron cyclotron resonance heating (ECRH) experiments in the interchangeable module stellarator (IMS), a small modular stellarator, can be modeled. In this they were guided by the experimental observation of large variations in potential around the magnetic surfaces, which can give rise to radially directed E×B convective flow. A diffusion model based on small-scale convective cell structures cannot simulate the experimental profiles. Including a purely convective term in the particle balance equation allows for a much-more-accurate modeling of the profiles. A comparison between numerical and experimental results is presented