About reflection diffraction radiation oscillator operation at second space harmonic

Potentials for start current decrease in RDRO operating at second harmonic has been shown both theoretically and experimentally. In contrast to case of first harmonic operation in the case of second harmonic one (at constant period) the EB velocity spread essentially decrease interaction power. If EB voltage is constant when period is increased the flight angle remains the same and EB velocity spread has the same effect both at first and second harmonic operation.