Numerical results on 3-D particle-in-cell (PIC) simulations of a 16-vane strapped magnetron oscillator are presented. A mode spectrum of the 16-vane strapped magnetron cavity with a ceramic (alumina, epsilon(r) = 9.8) ring tuner is obtained from the numerical code MAGIC3D. A wide mode separation of 21% between the pi-mode and the nearest mode is observed in the 16-vane strapped configuration. An electron beam flow exhibits eight spokes in the PIC simulation, which is a typical characteristic of pi-mode oscillation in the 16-vane magnetron. Simulation predicts that radiated RF power at the output port is 1114 W at 9.12 GHz, corresponding to a magnetron efficiency of 22.5% where the axial external magnetic field is 4.6 kG and the beam voltage and current are 2.6 kV and 1.9 A, respectively. (c) 2005 Elsevier B.V. All rights reserved.