Design of a Second Harmonic Double-Beam Continuous Wave Gyrotron with Operating Frequency of 0.79 THz

Abstract

This paper presents the most essential steps of a design study of a novel second harmonic gyrotron operating in CW (continuous wave) regime at a frequency of 0.79 THz and an output power of 1-100 W. It is based on a novel idea for suppression of the parasitic modes using a double-beam electron-optical system (EOS). It includes a triode magnetron injection gun (MIG), which forms two high-quality helical electron beams (HEB). Different schemes, namely one with two generating beams and another with one generating and one absorbing beam, have been investigated and compared. It has been shown that the scheme with two generating beams is more advantageous since it allows an effective suppression of the parasitic modes and a stable single-mode operation at the second harmonic resonance. A MIG which is appropriate for the realization of the latter scheme has been optimized using numerical codes for computer-aided design (CAD). It forms beams with practically equal pitch factors and moderate velocity spread. The construction of the gun is not sensitive to small misalignments and shifts of the electrodes and the magnetic field. Among the most promising characteristics of the presented design are an improved mode selection and a stable single-mode generation at currents that are two to three times higher than the currents in the single-beam (i.e., conventional) gyrotrons.

Second Harmonic 527-GHz Gyrotron for DNP-NMR: Design and Experimental Results

“…However, pushing the frequency into the sub-THz and THz range poses new challenges such as operation in the higher electron cyclotron harmonics, reduced efficiency, frequency tunability, high ohmic loss and higher operating mode competition etc. Despite these challenges, there is an intense interest in developing gyrotrons for DNP applications due the vast potential of the DNP technique to revolutionize the field of NMR spectroscopy [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44].…”