Beam-Surrounding Interactions and the Stability of Relativistic Particle Beams

In accord with recent custom, the organizing committee for this conference has scheduled this review paper on beam instabilities. In view of the various review papers which already exist and the fact that the fundamentals of the subject have even been treated in a textbook, I thought this paper might best be devoted to a limited part of the rather large field of beam instabilities. Thus, I have selected only an aspect of the general subject, but an aspect which has during the last years been very much at the center of activity, and will--if my judgment is correct--be even more so in the years to come. I wish to concentrate, here, on the interaction of a relativistic particle beam with itself which is a result of the coupling of the beam with its surroundings. Before approaching this topic, a few remarks on the existing review papers are in order. A comprehensive treatment of beam instabilities may be found in Ref. 1, where, also, the reader will find some 48 references to the original literature. In Refs. 2 and 3, the General subject is approached from other points of view. Reference 4 is concerned with some special topics, but treats them in depth; and the text of Ref. 5 closely follows the original papers.