The features of diffraction radiation oscillator operating on the 1st Gaussian mode of the open resonant system

To decrease weight and sizes of diffraction radiation oscillator (DRO) it's necessary to use a small-sized open resonant system (ORS). In the present paper is shown, that in small-sized DRO, operating on the 1
^st
Gaussian mode in ORS (TEM
₀₀₁
-mode) with minimal field spot, it managed to reduce the effect of regrouping in electron beam and significantly reduce device sizes along the focused magnetic field. In a small-sized DRO due to radiation loss decreasing in the ORS the combined frequency tuning range extension is reached and there is an extension of electronic frequency tuning range due to reducing of ohmic Q-factor in the small-volume ORS. The theoretical (using a 2-D model of ORS) and experimental results of investigations of the resonant modes properties in a small-sized ORS with periodic structure in form of double grating, are given. The comparative analysis of output characteristics of small-sized DRO operating on the 1
^st
Gaussian mode, with standard DRO operating on TEM
₀₀₄
-mode, is presented.