Long lepton bunch self-modulation experiment at SLAC

The use of long particle bunches to drive ultra-relativistic, high amplitude plasma waves through the transverse self-modulation instability (SMI) has been recently investigated numerically. This has motivated proton driven plasma wakefield accelerator experiments currently being planned at CERN and Fermilab. We propose to explore the SMI using the 20 GeV, 500 microns long lepton bunches currently available at SLAC FACET. Full-scale PIC simulations show gradients greater than 20 GeV/m and up to 10 GeV energy gain/loss at the 1{\%} level in 1 meter plasmas using electron bunches. Simulations show that the blowout regime is reached at the saturation of the SMI. For the positron driven scenario, the blowout leads to the defocusing of most of the positrons and a gain/loss up to 5 GeV at the 1 {\%} energy level is reached. Simulation results as well as diagnostics to measure the SMI in the planned experiments are discussed.