Design of an X-Band Bunching and Accelerating System for AWAKE Run 2

In Run2 AWAKE aims to demonstrate beam quality and increase the accelerating gradient in the plasma even further and in order to be able to serve high-energy physics experiments. In this framework, a new electron injector, consisting of an S-band RF-gun and a subsequent X-band bunching and accelerating sections, able to produce very short bunches with a small emittance, has been designed. In this paper, two different configurations of the X-band section and their corresponding high power distribution systems are presented. The first one consists of three identical travelling wave cavities to bunch and accelerate the beam while the second one uses a separate short structure for velocity bunching followed by three long pure accelerating structures. A discussion of the strengths and weaknesses of each configuration is carried out; the X-band power distribution systems are described with particular attention to the choice of the high-power klystron, the pulse compression system and the waveguide distribution.