Grooved multi-stage depressed collector for secondary electron suppression

Abstract

A linear beam device comprises a cathode and an anode spaced therefrom, with the anode and cathode being operable to form and accelerate an electron beam. An RF interaction region having a drift tube is arranged relative to the anode to permit the electron beam to pass therethrough. A multi-stage depressed collector of the linear beam device has a plurality of collector electrodes successively arranged to collect spent electrons of the electron beam after passing through the RF interaction region. Each one of the plurality of collector electrodes has a distinct voltage level applied thereto defining a decelerating electric field within the collector. At least one of the plurality of collector electrodes further comprises a collecting surface having a shape that is normal to a coincident trajectory of the spent electrons, whereby a substantial portion of the collecting surface is covered with a plurality of narrow grooves. In an embodiment of the invention, the grooved collector electrode further comprises the final electrode of the collector. The final electrode has a surface that is substantially spherical, and the plurality of grooves may be arranged in a concentric pattern of circles on the electrode surface. The plurality of grooves may be formed to a depth that is approximately twice a corresponding width. A region adjacent to an opening of each of the plurality of grooves comprises electric fields defining a convergent lens, thereby focusing the spent electrons into the plurality of grooves.