Witness gun for the Argonne Wakefield Accelerator

In order to probe the wakefields of the Argonne Wakefield Accelerator (AWA) a beam of medium energy (4-6 MeV) and relatively low charge (100 pC-1 nC) is needed. Two options for a witness gun meeting these specifications are currently under study. The first is a conventional iris loaded multicell gun. The second is a dielectric-lined cylindrical cavity operating in a pure TM/sub 01n/ mode. Since a more accurate probing of the wakefields can be obtained by improving the witness beam quality, this factor of merit will determine which gun is better suited for the experiment. It is thought that a brighter beam may be obtained using the dielectric gun. Since the dielectric gun will operate in a single accelerating mode, higher order modes will not be present. This in turn may lead to a slower emittance growth. This potential benefit comes at the cost of a lower cavity Q and dielectric charging considerations. Details of design, bench test and simulation results will be presented.<
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