AWAKE: proton-driven plasma wakefield acceleration for particle physics.

We describe progress made by AWAKE towards an accelerator concept that uses self-modulation (SM) of a long, 400GeV proton bunch in plasma, to accelerate electrons, in a single plasma, to energies suitable for application to particle and high-energy physics. These include: Demonstration of the SM process and of its seeding with two methods; Observation of its growth along the bunch and plasma (using an optical diagnostic), and of suppression of the growth by imposing a density gradient; The effect of ion motion on the SM process, and; acceleration of test electrons to the GeV energy level. We also observed two other instabilities: the hose (for the first time) and the filamentation instabilities, both when purposely triggered. Based on these results, we developed a plan to demonstrate first, the external injection and acceleration with quality of an externally injected electron bunch in a two-plasma system, second, the scalability of the acceleration in a new plasma source developped in the context of this project. First particle physics experiments using a plasma-based accelerator could occur in the 2030's.