Transverse focussing using plasma wake fields

Dense particle beams travelling in plasmas can produce very high electric and magnetic fields, and these fields can be used to accelerate and focus particles. The effects on trailing beams and self focusing can be strong and nonlinear. This paper discusses two aspects of self pinching beams: 1) the production of beams which do not self pinch, and 2) a short focal length plasma lens which uses self pinching to reduce beam sizes at the interaction point of a linear collider. As an example, the authors consider a final focus system for the Stanford Linear Collider, considering plasma production, vacuum system and backgrounds, and show how the luminosity could be increased using this system. The authors also discuss experimental tests of the plasma lens concept