Impurity ions are deliberately seeded into fusion plasmas for a variety of purposes. From the earliest days of magnetic-confinement fusion energy research, the spectra of light impurity ions, such as those of helium, lithium and carbon were used as a diagnostic tool to determine plasma properties. With the advent of very large scale experimental devices such as ITER, impurity injection is increasingly being used to redistribute the power transported from the plasma core to the reactor wall in order to reduce the heat load on, and hence damage to, the plasma-facing reactor wall components. Furthermore, impurities such as nitrogen, neon and argon and have been used in such devices to improve plasma control by diminishing the amplitude of edge-localized modes (ELMs), plasma disruptions and other transient events that inhibit confinement and have the potential to cause serious damage to wall components.
In order to interpret and predict the behaviour and properties of impurities in fusion plasma, a significant amount of modelling, involving data on the collisional-radiative characteristics of the impurities and their environment is required. For a few species, high-quality data is available, but in many cases the currently-available data is incomplete, missing, or of uncertain quality.
This planned CRP will provide fundamental data for modelling the behaviour of first-row and noble gas atoms in edge and divertor plasmas for ELM and disruption mitigation and for plasma diagnostics, and establish a trusted repository of data concerning the collisional–radiative properties of plasma–impurity interactions to facilitate modelling of plasmas in magnetic confinement fusion devices.