Control of impurities in controlled fusion machines

Recent advances in Tokamak research have given promise that the next generation of machines may approach break even conditions. Nonetheless, calculations show that quasi-steady state fusion reactors may be plagued by high Z impurities causing intolerable radiation losses. The present state of knowledge concerning impurity release rates and mechanisms resulting from plasma-materials interactions as well as impurity transport and detection diagnostics, is reviewed. Various impurity control methods are discussed which either are being currently used or have been proposed and are in the development stage. The paper attempts to convey to the non-specialist an impression of the magnitude and importance of the impurity control problem and points to areas where plasma chemical insights can aid in the development of better approaches to impurity control