Project of medium-power sub-terahertz gyrotron with smooth wideband frequency tuning for spectroscopy of forbidden transitions

To achieve smooth broadband frequency tuning in the gyrotron, we propose to use a short cavity with a low operating mode, driven by an electron beam with a sufficiently high current. Analytical estimations and numerical calculations show that the short length of the cavity reduces the sensitivity of the gyrotron to velocity spread for frequencies far from cutoff. As a result, a sequential effective excitation of a number of axial modes is possible with magnetic field change. On the basis of the averaged equations and three-dimensional codes, the generator operating on the TE
_1,3
model and capable of providing an output power of more than 200 W in a band of more than 4 GHz near the 163 GHz frequency was designed. For this gyrotron, a magnetron-injector gun and a built-in direct converter of the operating mode to the TE
_1,1
mode of circular waveguide were developed. The gyrotron is planned to be used for molecular spectroscopy of forbidden transitions using a radio-acoustic detector.