Frequency characteristics of TE11 mode enhanced coaxial vircator

Due to poloidal-asymmetry electron emitting, TE
11
mode output of high-power microwave (HPM) is unavoidable in coaxial vircator. In order to obtain a pure mode output, TE
11
mode enhanced design by opposed section electron emitting is applied with more advantages. As two-dimensional effect along poloidal direction is coursed, the frequency of microwave generated is shifted in TE
11
mode enhanced coaxial vircator compared with the thoroughly coaxial one. Frequency characteristics of TE
11
mode enhanced coaxial vircator are studied numerically by the 3-D particle-in-cell (PIC) code UNIPIC and experimentally on a high-power pulse modulator. Simulations results show that a stable TE
11
mode output is generated nearly with a point frequency in TE
11
mode enhanced geometry, which is a little lower than that in the thoroughly coaxial geometry. In experiments, nearly point frequency and stable TE
11
mode output is also obtained and the effect of diode voltage, anode-cathode gap and electron beams width are investigated. The results show that with higher diode voltage, smaller anode-cathode gap and larger electron beams width, the frequency of microwave generated is higher, especially electron beams width has the same degree effect with diode voltage and anode-cathode gap, which is well agreed with simulation results.