Numerical Simulation Study of Double-Beam Magnetron-Injection Guns for High-Power Gyrotrons

This paper describes the detailed design of the double-beam coaxial magnetron-injection gun (DBMIG) for use in Ka-band coaxial gyrotron with two beams operating in the harmonic mode. The DBMIG operating voltage is 70 kV with a total beam current of 20 A, evenly divided among the beamlets, and provides two 70-kV 10-A beams with a velocity ratio of 1.5. The minimum of the transverse velocity spread and the axial velocity spread are about 3% and 5%, respectively. The emitter current density has been kept below 10 Amiddotcm
^-2
(space-charge limited). The primary computational tools used in the design process were the self-consistent particle-in-cell simulation code MAGIC