Performance of the Argonne Wakefield Accelerator facility and initial experimental results

Abstract

The Argonne Wakefield Accelerator (AWA) facility has begun its experimental program. This unique facility is designed to address advanced acceleration research which requires very short, intense eiectron bunches. The facility incorporates two photocathode based electron sources. One produces up to 100 nC, multi-kiIoamp 'drive' bunches which are used to excite wakefieids in dielectric loaded structures and in plasma The second source produces much lower intensity 'witness' pulses whch are used to probe the fields produced by the drive. The dnve and witness pulses can be precisely timed as well as laterally positioned with respect to each other. We discuss commissioning, initial experiments, and outline plans for a proposed 1 GeV demonstration accelerator. Overview of the AWA FacilityThe generation of high gradients (> 100 W / m ) in wakefield structures requires a short pulse, high intensity electron drive beam. The main technological challenge of the AWA program is the development of a photo injector capable of fulfilling these requirements. The goal of the AWA is to demonstrate high gradient and sustained acceleration of charged particle beam by using wakefield method. In the past year we have made considerable progress towards attaining the design goals of the AWA. In this paper we present detailed descriptions of the facility and initial characterization of its performance. The preliminary results of dielectric and plasma wakefield experiments are discussed. The near and long term plans for experiments and facility upgrades wilI be described. Photocathode Gun and Drive Linac SystemThe gun and drive Iinac are shown in Fig. 2. The laser photocathode sources was designed to deliver 100 nC bunches at 2 MeV to the dnve h a c . The photocathode gun is a single cell standing wave cavity with designed peak fieid of 90 MV/m on the cathode [l]. Some of the novel features incorporated into the ** gun to attain high intensities include a Large (2 cm diameter) cathode, the use of a curved laser wave front and nonlinear focusing solenoids matched to the angleenergy correlation computed for the 100 nC bunch.

Limiting effects in drive bunch beam dynamics in beam-driven accelerators: instability and collective effects

“…Various ideas for the slow wave medium have been proposed and explored, and the most common concepts are a dielectric loaded slow-wave structure, a corrugated waveguide, or a chamber filled with plasma. The conceptual schematic of the collinear dielectric wakefield accelerator (DWA) [4,6,7] is shown in figure 1. A low-energy, high-charge drive electron bunch (𝑄 1 ) produces a wakefield in a dielectric-lined waveguide (DLW).…”