Enhancement of overall efficiency in large-orbit gyrotrons
Abstract
Energy recovery from the spent beam in gyrotrons can enhance their overall
efficiency. A technique for converting the rotational motion in the spent beam of
a large-orbit gyrotron into axial motion, before leading it into a retarding
electrostatic field generated by depressed collectors is proposed. This involves
passing the spent beam through a magnetic cusp. A proof-of-principleexperiment
has been performed which verifies the prediction regarding unwinding of the
beam, and its collection at a depressed potential which is higher than would
otherwise be possible. The experimental set-up and results are presented. A
multi-stage depressed collector for a large-orbit gyrotron bas also been designed.
Primary electrons representing beamlets of a range of energy values are collected
at different depressed potentials after energy sorting. Any turning around of
primaries before collection has been eliminated and almost all the back-scattered
electrons are re-absorbed either on the same collector or on an adjacent one. A
collector efficiency of 70 to 80";'; has been estimated.