The Advanced Wakefield Experiment (AWAKE) recently demonstrated that: 1) a 400 GeV/c proton bunch (with a bunch length 30-100 times longer than the plasma electron wavelength) self-modulates over 10m of plasma; 2) externally injected ~20 MeV electrons can be accelerated to GeV energies in the resonantly excited wakefield. In this contribution, we show the results of an AWAKE experimental study: we measured the integrated amplitude of the longitudinal and transverse wakefields for different laser seed positions (the laser pulse is overlapped with the proton bunch to seed the self-modulation process) and electron delays (distance between the laser pulse and the externally injected electrons). By changing those parameters we change the initial seed level, the number of protons that contribute to driving the wakefields (and thus the growth rate of the self-modulation process) as well as the amplitude of the driven wakefields. We show that the accelerated electron energy and the transverse proton bunch distribution agree with the trends observed in numerical simulations as well as the expectations from simple considerations.
|Working group||Laser-driven electron acceleration|