Status of the proton and electron transfer lines for the AWAKE Experiment at CERN

J.S Schmidt,J Bauche,B Biskup,C Bracco,S Doebert,B Goddard,E Gschwendtner,L.K Jensen,O.R Jones,S Mazzoni,M Meddahi,K Pepitone,A Petrenko,F.M Velotti,A Vorozhtsov

doi:10.1016/j.nima.2016.01.026

Abstract

The AWAKE project at CERN is planned to study proton driven plasma wakefield acceleration with an externally injected electron beam. Therefore two transfer lines are being designed in order to provide the proton beam from the SPS and the electron beam from an RF gun to the plasma cell. The commissioning of the proton line will take place in 2016 for the first phase of the experiment, which is focused on the self-modulation of a 12cm long proton bunch in the plasma. The electron line will be added for the second phase of AWAKE in 2017, when the wakefield will be probed with an electron beam of 10–20MeV/c. The challenge for these transfer lines lies in the parallel operation of the proton, electron and laser beam used to ionize the plasma and seed the self-modulation. These beams, of different characteristics, need to be synchronized and positioned for optimized injection conditions into the wakefield. This task requires great flexibility in the transfer line optics. The status of these designs will be presented in this paper.

Highlights

Experiments with particle beam driven plasma wakefields are ongoing in several laboratories worldwide
The Advanced ProtonDriven Plasma Wakefield Acceleration Experiment (AWAKE) [1] is currently under development at CERN. It will be installed in the former CNGS (CERN Neutrinos to Gran Sasso) area, where a proton beam from the SPS (Super Proton Synchrotron) will serve as a drive beam for wakefields in a 10 m long plasma cell
When the proton bunch enters the plasma, which is ionized by a 4 TW laser pulse, it is expected to experience a self-modulation instability (SMI), creating micro-bunches with the plasma wavelength of 1 mm

Summary

Introduction

Experiments with particle beam driven plasma wakefields are ongoing in several laboratories worldwide. PHIN (the PHotoINjector from CTF3) [3], in combination with a 1 m long traveling wave linac, will be used to produce an electron beam with a momentum of 10–20 MeV/c This electron beam will be injected into the wakefield and its output energy is measured by a spectrometer dipole in the secondary beam line. In the last section of about 80 m, a chicane has been integrated in order to create space for a mirror of the laser beam line This is necessary to merge the ionizing laser pulse with the proton beam about 22 m upstream of the plasma cell so that they propagate coaxially. The spot size is defined by σ 1⁄4 β Á ε þðD Á Δp=pÞ2, taking into account the beta function β, the emittance ε, the dispersion D and the momentum spread Δp=p

The electron beam line

Optimized electron injection into the wakefield

Status and outlook