Garry McCracken gained a PhD in solid state physics but has spent most of his working life as an experimental physicist working on various aspects of the magnetic confinement fusion program with the UK Atomic Energy Authority at Culham Laboratory. His main interest has been in the study of the plasma boundary and in the interaction between the plasma and the surrounding structures and in studying the design of fusion reactors and the radiation damage problems which may be encountered. In 1979 he spent a year at the Plasma Physics Laboratory of Princeton University, USA, where he worked on the Princeton Large Tokamak. When the JET Joint Undertaking was set up as a European Fusion Laboratory… to build the JET experiment he led a Task Agreement on the plasma boundary physics. His group built and installed major diagnostics on JET and an active experimental programme was pursued. In 1993 he went to the Massachusetts Institute of Technology, USA and worked on the C-Mod tokamak in the Plasma Fusion Center. Returning to the UK in 1996 to work again on JET, until his retirement in 1999. He has published over 300 scientific papers including three major reviews in the general area of plasma-surface interactions. He was a regular lecturer at the Culham Plasma Physics Summer School until 1991 and has been invited to lecture at a number of other Summer school courses in Canada and Europe. During these latter lectures he began to feel that there was no adequate book to explain the subject of nuclear fusion to the staring physicist and engineer or the interested layman and set about writing the present book.