Development and Experimental Study of a Pulsed Megawatt Gyroklystron Operating in the Long-Wavelength Part of the Millimeter-Wavelength Range at IAP RAS

• Published in: Radiophysics and quantum electronics Vol. 64; no. 7; pp. 482 - 493
• Main Authors: Zasypkin, E. V., Gachev, I. G., Sokolov, E.V., Antakov, I. I.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.12.2021; Springer; Springer Nature B.V
• Subjects: Amplification; Astronomy; Astrophysics and Astroparticles; Bandwidths; Cryomagnetic properties; Efficiency; Electric potential; Hadrons; Heavy Ions; Lasers; Magnetic fields; Magnetic shielding; Mathematical and Computational Physics; Nuclear Physics; Observations and Techniques; Optical Devices; Optics; Photonics; Physics; Physics and Astronomy; Plasma physics; Pulse duration; Quantum Optics; Radiation; Self excitation; Solenoids; Theoretical; Voltage
• ISSN: 0033-8443; 1573-9120
• DOI: 10.1007/s11141-022-10149-4

We have developed and studied experimentally a two-cavity gyroklystron operating at a frequency of 35 GHz and the cavity mode TE 0 2 1 in a cryomagnet. The output radiation power achieved in the pulsed regime is 750 kW with an efficiency of 24%, a gain of 20 dB, and amplified-frequency bandwidth equal to 220 MHz (0.63%) at an accelerating beam voltage of 74 kV, a current of 42.5 A, and a pulse duration of 100 μs. An operating-frequency bandwidth equal to 310 MHz (0.89%) at a power level of 430 kW has been achieved in another variant of the gyroklystron. At fixed current and beam voltage, the limitation of the efficiency and the bandwidth of the operating frequencies is determined by self-excitation of parasitic oscillations in the output cavity at the TE 2 2 1 mode. The limitation of the highest power of the output radiation at a level of 750 kW is related to the formation of a high-frequency discharge in the output cavity because of the deterioration of the vacuum in it as a result of heating the internal surface of the cavity due to ohmic losses. Strong influence of the axial distribution of the static magnetic field in the interaction space on the efficiency and the output radiation power is predicted theoretically and demonstrated experimentally. By finding an optimal longitudinal structure of the magnetic field using solenoids and magnetic shields, we have managed to increase the efficiency and the power of the gyroklystron in the experiment by 1.3 times compared to the case of a homogeneous distribution of the magnetic field.