Dynamics of magnetic insulation violation in smooth-bore magnetrons

The efficiency of large and high-power magnetrons of GW power levels is less than 30% and inherent pulse-length and repetition rate limitations seem to exist because of use of explosive field emission. Another approach is the development of low voltage, high-efficiency magnetrons utilizing a secondary emission magnetron array with high repetition rate. The numerical model of nonstationary, nonuniform secondary electron emission from a cathode surface has been developed. The results of first steps in computer simulations of electron cloud formation inside a smooth-bore magnetron under the condition of back-bombardment instability (BKB) are presented. Calculations have been performed for a coaxial smooth-bore magnetron and for magnetrons with different types of azimuthal inhomogeneities which could promote the growth of BKB. The results of computer simulation are in agreement with experimental data. The main calculations of the beam dynamics were carried out with PIC-code KARAT.