Data base requirements for impurity and particle control models

One of the critical issues for the design and operation of ignition fusion experiments is impurity and particle control. An impurity and particle control system must be able to maintain a plasma reasonably free from impurities, have a reasonable lifetime, and provide adequate helium exhaust. The design of such a system requires extrapolations based on our present understanding of the physics and engineering derived from current and past experiments and theory. Some of the tools used to make such extrapolations are computational models which embody our current understanding, and are calibrated by their use in the analysis of current and past experiments. These computational tools are based on at least five sources of information. They are: 1. (1) a general description of the behavior of plasma experiments with regard to impurity and particle control issues, 2. (2) specific sets of experimental data which are sufficiently complete that they can be analyzed using the computational models, 3. (3) the theoretical work and numerical methods that allow a model to be formulated into a set of equations and boundary conditions, and those equations to be solved, 4. (4) a quantitative description of the atomic collision phenomena that occur in edge plasmas, and 5. (5) data for reflection, sputtering, and desorption to describe the interaction of ions and neutrals with surfaces. All of these ingredients contribute in a key way to the computational tools used to analyze and guide the design of impurity and particle control systems for the next generation of fusion experiments.