An experimental test of the theory of the stimulated dielectric wakefield accelerator

We have installed a dielectric-lined wakefield accelerator at the Accelerator Test Facility (ATF), Brookhaven National Laboratory. The first experiment, reported here, uses a single 0.2 nC, 10 psec bunch of 40 MeV electrons to excite the multi-mode TM/sub 0m/ wakefields which trail the bunch. The device is configured as a cylindrical waveguide containing an annular alumina liner; the electrons move along the axis of symmetry inside a 3 mm diameter bore hole. The spectrum of modes set up by the electron bunch is picked up by a radial probe and detected by a spectrum analyzer; this is compared with theory. This spectrum can be used to construct the axial wakefield pattern.