Application of plasma lenses to the AWAKE interstage

Abstract

A future possible acceleration technique for linear colliders is plasma wakefield acceleration. One of the questions unanswered today is whether we can use this technology to achieve TeV-scale acceleration with a good enough beam quality. The AWAKE-experiment at CERN has as goal to demonstrate the feasibility of TeV acceleration using an SPS proton beam as a plasma driver. For Run 2 of AWAKE we need to self-modulate the proton beam before we inject an electron witness beam in the acceleration stage. This creates a interstage between the two plasma cells, where the proton beam needs to be refocused in a limited space. We have looked at plasma lenses as a solution to this problem, since they both deliver stronger magnetic fields and have axisymmetric focusing compared to conventional magnetic quadrupoles. We have in particular studied nonlinear effects; nonlinear magnetic field due to non-uniform current distribution, and wakefields originating from the charged beam being focused. In a relation to a pre-study of plasma lenses at the CLEAR-facility at CERN, we have studied where the wakefield is significant, in preparation for further experimental verification at CLEAR. We have then studied whether plasma lenses can be used for an AWAKE interstage. The results with and without nonlinear effects are the same: to use plasma lenses we need improved plasma lenses with respect to today's state of the art. However, assuming higher current and longer lenses than available today, plasma lenses could potentially be interesting for the AWAKE interstage.