Application of a plasma lens to e γ colliders

We describe the focusing of a charged particle beam by a plasma and its application to e γ colliders. After reviewing the issues involved in the final focus and interaction point design for e γ colliders we compare the luminosities for e γ colliders in different scenarios. Using a plasma lens to defocus the spent beam is shown to yield higher luminosity than deflecting the beam with a bending magnet. The possibility of configuring the NLC (Next Linear Collider), and the SLC (Stanford Linear Collider) as e γ colliders is considered together with the physics motivations. It is shown that only with a strong lens, like a plasma lens, is it possible to achieve the desired luminosity.