CONTRIBUTION OF THE SURFACE PLASMON TO ENERGY LOSSES BY ELECTRONS IN A CYLINDRICAL CHANNEL.

The surface-plasmon contribution to the energy losses experienced by an electron beam in a cylindrical channel in a metal is derived. The work is motivated in part by considerations relevant to an electron ring accelerator. The nonrelativistic limit is used for convenience in order to display the effect in a simpler manner. A relativistic derivation previously given by Merkel, which includes only ohmic losses, may be improved upon with the methods shown here. Surface-plasmon energy losses are included in the nonrelativistic limit, but it is well known that surface-plasmon excitation increases with increasing beam energy well into the kev regime. The results obtained here can be generalized to the relativistic case quite easily and show how the optical properties of the metal surrounding the channel affect the energy losses.