Analysis of Dual-Frequency Radiation From a ${G}$ -Band Extended Interaction Oscillator With Double Sheet Beam

The dual-frequency radiation scheme of a ${G}$ -band extended interaction oscillator (EIO) has been proposed. The analytic estimates of structure, mode characteristics, and oscillation-starting condition of the overmoded double-sheet-beam oscillator have been presented. The counterstreaming beams and optimized parameters were employed to reduce the fundamental mode competition in a TM21 mode EIO, allowing the high-order transverse mode ( ${\text {TM}}_{{21}}^{+-}$ ) and the fundamental mode ( ${\text {TM}}_{21}^{++}$ ) to operate simultaneously. The analyses are verified by simulations using 3-D particle-in-cell codes. The newly designed EIO was simulated with copper as a background material, and the dual-frequency radiation power of ~517 W is achieved when a double electron beam with 0.4 A and 21.5 kV is injected.