Non-diffusive transport modeling: statistical basis and applications

Abstract

The key issue to achieve controlled fusion is to confine a very high temperature plasma for a sufficiently long time. However, plasma confinement is limited by thermal transport processes, and therefore, one of the main goals of plasma physics research is to understand transport. Coulomb collisions provide the most basic, and natural transport mechanism in a plasma. However, transport calculations based only on coUisional effects (i.e., classical and neoclassical transport theories) tend to underestimate the transport levels experimentally observed in magnetically confined fusion plasmas. It is believed that plasma instabilities and turbulence play a critical role in the observed enhanced transport. The study of turbulence-driven transport, also known as anomalous transport, has therefore attracted a lot of attention. Although significant progress has been made in the classical, neoclassical, and anomalous theories of transport, there are important open problems likely to play a role in the design and operation of present and future fusion devices including ITER. A common feature of these problems is that they seem to defy our intuition rooted in the concept of diffusive transport.