The Argonne Wakefield Accelerator: diagnostics and beam characterization

Abstract

The Argonne Wakefield Accelerator is comprised of two L-band photocathode RF guns and standing wave linac structures. The high charge bunches (20 -100 nC) produced by the main gun (drive gun) allow us to study the generation of wakefields in dielectric lined structures and plasmas. The secondary gun (witness gun) generates low charge bunches (80 -300 pC) that are used to probe the wakefields excited by the drive bunches. We use insertable phosphor screens for beam position monitoring. Beam intensity is measured with Faraday cups and integrating current transformers. Quartz or aerogel Cerenkov radiators are used in conjunction with a Hamamatsu streak-camera for bunch length measurements. The beam emittance is measured with a pepper-pot plate and also by quadrupole scan techniques. We present a description of the various diagnostics and the results of the measurements. These measurements are of particular interest for the high current (drive) linac, which operates in a much higher charge regime than other photoinjector-based linacs.