Experimental and numerical studies of dielectric wake field acceleration devices

Results are reported from experiments, and numerical analysis of wake fields set up by electron bunches passing through a cylindrical dielectric liner made of alumina. The bunches excite many TM-modes, and the Ez component of wake field is sharply localized on the axis periodically behind the bunches. The experiment is at ATF Brookhaven, and uses up to three 50 MeV bunches spaced by one wake field period (21 cm) to study the superposition of wake fields by measuring the energy loss of each bunch after it passes through the 53-cm long dielectric element. The millimeter-wave spectrum of radiation excited by the passage of bunches is of interest too. The numerical analysis was aimed not only to simulate the behaviour of our device, but in general to predict dielectric wake field accelerator (DWA) parameters. It is shown that one needs to match the radius of dielectric channel with the bunch longitudinal rms-length to achieve optimal performance.