Study of an energy recovery system for a large-orbit gyrotron

An approach to energy recovery from the spent beam of large-orbit gyrotron is outlined that uses a double magnetic cusp arrangement. The first cusp produces a large rotational velocity, while the second cusp unwinds the axis-encircling beam before it proceeds toward depressed collectors. The results of numerical simulations for beam transmission through the two cusps are summarized. An experimental setup for proof of principle is described. Results are presented in the form of the depressed potential on a Faraday cup versus the current collected by it. Current collection is observed up to larger depressed potentials when the second cusp is introduced, as compared with the case where field reversal is not introduced, thus verifying the concept. A design for multiple depressed collectors is presented along with the trajectories in the collector region.