Advanced magnetron injection guns

Abstract

This paper describes the improvement of mission uniformity in magnetron injection guns (MIGs) for gyrotrons, and on an inverted MIG for a Ku band coaxial gyrotron. High-power gyrotrons and gyroklystrons are currently in development for a number of RF applications. The annular electron beams for these devices are created with a MIG operating temperature limited, which means the emission current is a function of the localized temperature. Efficient operation of gyrotrons and gyroklystrons requires a high-quality electron beam with low-velocity spread and uniform current density around the circumference of the beam. Advances in computer modeling allow design of electron guns with velocity spreads less than 8%, which is adequate for efficient operation; however, there is substantial evidence that large azimuthal asymmetries in current emission often occur. This can lead to substantial reductions in device efficiency.