The electron accelerators for the AWAKE experiment at CERN—Baseline and Future Developments

Pepitone, K. and Doebert, S. and Apsimon, Robert James and Bauche, J. and Bernardini, M. and Bracco, C. and Burt, Graeme and Chauchet, A. and Chevallay, E. and Chritin, N. and Curt, S. and Damerau, H. and Kelisani, M. Dayyani and Delory, C. and Fedosseev, V. and Friebel, F. and Galleazzi, F. and Gorgisyan, I. and Gschwendtner, E. and Hansen, J. and Jensen, L. and Keeble, F. and Maricalva, L. and Mazzoni, S. and McMonagle, G. and Mete, O. and Pardons, A. and Pasquino, C. and Verzilov, V. and Schmidt, J.S. and Soby, L. and Williamson, B. and Yamakawa, E. and Pitman, Sam and Mitchell, James (2018) The electron accelerators for the AWAKE experiment at CERN—Baseline and Future Developments. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 909. pp. 102-106. ISSN 0168-9002

Abstract

The AWAKE collaboration prepares a proton driven plasma wakefield acceleration experiment using the SPS beam at CERN. A long proton bunch extracted from the SPS interacts with a high power laser and a 10 m long rubidium vapor plasma cell to create strong wakefields allowing sustained electron acceleration. The electron beam to probe these wakefields is created by an electron accelerator consisting of an rf-gun and a booster structure. This electron source should provide beams with intensities between 0.1 and 1 nC, bunch lengths between 0.3 and 3 ps and an emittance of the order of 2 mm mrad. The booster structure should accelerate the electrons to 16 MeV. The electron line includes a series of diagnostics (pepper-pot, BPMs, spectrometer, Faraday cup and screens) and an optical transfer line merges the electron beam with the proton beam on the same axis. The installation of the electron line started in early 2017 and the commissioning will take place at the end of 2017. The first phase of operation is called RUN1. After the long shutdown of LHC a second phase for AWAKE is planned starting 2021 called RUN2. In this phase the aim is to demonstrate the acceleration of high quality electron beams therefore a bunch length of the order of 100 fs rms is required corresponding to a fraction of the plasma wavelength. The AWAKE collaboration is studying the design of such an injector either based on classical rf-gun injectors or on laser wake-field acceleration. The focus for the RF accelerator is on a hybrid design using an S-band rf-gun and x-band bunching and acceleration cavities. The layout of the current and the future electron accelerator and transfer line, including the diagnostics will be presented.