Development of the Second Harmonic Dual Mode Gyrotron for OAM Beam Generation

A novel scheme of orbital angular momentum (OAM) beam generation in radio frequency (RF) range using gyrotron is demonstrated. The gyrotron generates few kilowatts of power at 190 GHz frequency in a second harmonic mode-pair $\mathbf{TE}_{\pmb{8,3}}/\mathbf{TE}_{\pmb{17,2}}$ from 33/37 kV, 7 A electron beam. It incorporates the two sinusoidal perturbations in the cylindrical cavity to eliminate the fundamental mode competition. These high-power OAM beams can be used for free space RF communication and RF beam plasma interaction.