The operating characteristics of the 100 GHz linear magnetron employing the reentrant resonator are investigated by using a two-dimensional particle-in-cell simulation. The geometrical parameters calculated for the operation frequency of 100 GHz are confirmed by the resonant modes and field distribution obtained by an electromagnetic simulation. With the synchronism condition, the effect of number of vane and beam voltage on the power density and the operation frequency are examined. When the beam voltage of 2 kV and the external magnetic field of 0.79 T are used, the reentrant linear magnetron is oscillated at about 100.2 GHz, and the maximum power density with the injected current density of 60 A/cm(2) is increased up to 220 mW/mm(2) from 125 mW/mm(2) due to the extension of interaction region as the number of vane is varied from 10 to 12. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3072885]