Experimental study of wakefields in an X-band photonic band gap accelerating structure

Abstract

Abstract.We designed an experiment to conduct a detailed investigation of the higher order mode spectrum in a roomtemperature traveling-wave photonic band gap (PBG) accelerating structure at 11.7 GHz. It has been long recognized that PBG structures have great potential in reducing long-range wakefields in accelerators. The first ever demonstration of acceleration in room-temperature PBG structures was conducted at MIT in 2005. Since then, the importance of that device has been recognized by many research institutions. However, the full experimental characterization of the wakefield spectrum in a beam test has not been performed to date. The Argonne Wakefield Accelerator (AWA) test facility at the Argonne National Laboratory represents a perfect site where this evaluation could be conducted with a single high charge electron bunch and with a train of bunches. The PBG structure was built and consists of sixteen 2 /3 traveling-wave cells, including two coupler cells. In this paper we will describe fabrication and tuning of the PBG cells, and the results of the final cold-test of the traveling-wave accelerating structure. Next we will discuss the plan for the wakefield experiment.

Observation of Wakefield Suppression in a Photonic-Band-Gap Accelerator Structure

“…Next, the cells were put together in a structure of 2 coupler cells and 14 traveling-wave cells. The clamped structure was cold-tested, and the final cold test results are described in [12]. The coupling curves for the tuned structure are shown in Figure 2 with the dip in the transmission curve at 11.697 GHz (in air) corresponding to the accelerating 2π/3 mode.…”

“…The coupling curves for the tuned structure are shown in Figure 2 with the dip in the transmission curve at 11.697 GHz (in air) corresponding to the accelerating 2π/3 mode. The electroformed PBG cells could not be brazed due to internal stresses [13]. After numerous discussions, a vacuum-compatible Hyson EA9394 epoxy was identified as means to join the cells together.…”