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Nonlinear Cyclotron Resonance Absorber for a Microwave Subnanosecond Pulse Generator Powered by a Helical-Waveguide Gyrotron Traveling-Wave Tube
摘要： A well-known principle for periodical production of high-power ultrashort optical pulses is related to passive mode locking realized when a saturable absorber is incorporated into the laser resonator. A similar effect can be implemented in two-section electronic oscillators comprising an amplifier and a saturable absorber, which should be applicable in the microwave frequency band and suitable for high-power operation. In this paper, we analyze in detail the possibility of realizing a saturable absorber based on cyclotron resonance interaction in the regular waveguide with initially rectilinear electron beam, when saturation is caused by the relativistic dependence of the gyrofrequency on electron energy. Maximum contrast between the absorption of a high-power signal and of a weak signal is achieved in the group synchronism regime when the particle velocity is close to the wave’s group velocity. Within the frame of a time-domain self-consistent model, we demonstrate that when such an absorber is installed in the feedback loop of an electron generator powered by existing Ka-band helical-waveguide gyrotron traveling-wave tube, periodical generation of subnanosecond pulses can be provided with peak power up to several hundred kW and sub-GHz repetition frequency. We discuss the influence of deviation from the group synchronism regime on the parameters of generated pulses. Experimental feasibility of the considered scheme is verified based on three-dimensional particle-in-cell simulations.
关键词： gyrotron traveling-wave tube,cyclotron resonance,subnanosecond pulse,saturable absorber,microwave
更新于2025-09-23 15:19:57
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Studies of a Gyrotron Traveling-Wave Tube with Helically Corrugated Waveguides at IAP Ras: Results and Prospects
摘要： The gyrotron traveling-wave tube (gyro-TWT) is a wideband version of gyrotron amplifiers, which produce pulsed or continuous-wave radiation in the millimeter-wavelength band at a power level that exceeds the powers produced by conventional TWTs with slow-wave structures and rectilinear beams by 1–2 orders of magnitude. Since 1996, researchers at the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) have been developing the concept of the gyro-TWT based on the use of a waveguide with a helically corrugated surface, which changes the dispersion of one of the eigenmodes in a circular waveguide radically. In this paper, we discuss several problems that arise in implementation of such devices, which many years of experimental studies have revealed, present the parameters of gyro-TWTs developed with allowance for specific applications of their end users, and discuss lines of further perfection of such amplifiers.
关键词： gyrotron traveling-wave tube,helically corrugated waveguide,high-power amplifiers,gyro-TWT,millimeter-wavelength band
更新于2025-09-19 17:13:59