Wednesday 12 October 2011 Speaker: Ted Wilson (CERN and the John Adams Institute, Oxford) Title: Accelerators for the future Abstract: Rutherford, Lawrence, Cockcroft, Walton, Alvarez, Oliphant, MacMillan, Richter, R.R Wilson, Wiik and Rubbia were physicists who, inspired by the goals of their own research, were stimulated to invent new acceleration techniques to achieve their ends. Modern physics has perhaps become too sophisticated now for individual imaginations to encompass both these creative activities. However, today's particle physicists will soon have to decide in which direction their research should lead them and make judgements on how they may be best served by future accelerators - whether future colliders should be linear or circular, whether energy or intensity is of greater importance - which particles: electrons protons, muons or neutrinos are of greatest interest. The choice must depend on the practical and affordable limits to each kind of machine. This talk will provide enough insight into the theory and design of accelerators to enable particle physicists to appreciate the limits to one of these kinds of machine: the circular collider. Starting from the parameters which determine the luminosity and physics performance of the LHC: energy, intensity, bunch structure and transverse beam size, we will explore the basic theory of phase stability, betatron motion, instabilities and beam-beam forces behind each of these parameters.