| In this thesis I describe the design, construction, and performance of the low energy photocathode gun generated electron beam (witness beam) for the Argonne Wakefield Accelerator (AWA). The mission of the AWA is to explore ultra-high gradient wakefields in both dielectric structures and plasmas. The witness beam probes the wakefields excited by the AWA's high charge photoelectron gun generated beam (drive beam). Witness beam design is driven by the requirements of the probe needed to measure these large acceleration gradients. With the use of several numerical codes to model the electromagnetic fields and beam dynamics, a six-cell, {dollar}pi{dollar}/2, standing-wave photocathode gun operating at 1.3 GHz is built. It is found that all models agree well with measurements and a high quality beam is produced: an energy of 4.0 MeV, a charge of 100 pC, a normalized emittance of 3.5 {dollar}pi{dollar} mm-mrad and a FWHM pulse length of 10 ps. The achromatic and isochronous beam lines for delivering the drive beam and the witness beam to the experimental test section are detailed herein. Theoretical investigations into an alternative dielectric photocathode are presented in the appendix. The witness beam is used to measure the first wakefields produced at the AWA, and these measurements are found to agree with theory. |
