Studies of a Gyrotron Traveling-Wave Tube with Helically Corrugated Waveguides at IAP Ras: Results and Prospects

IEEE Trans. Electron Devices

Avramidis

Feuerstein

et al. 2022

A new self-consistent time-domain model for the simulation of gyrotron traveling wave tubes with a helically corrugated interaction space (helical gyro-TWTs) is presented. The new model links classical methods, using the approach of slowly varying variables together with an expansion of the electromagnetic field in eigenmodes, and advanced full-wave PIC solvers. The aim is to significantly reduce the required calculation time compared to full-wave PIC solvers, while less strict assumptions are introduced as in the classical approaches of slowly varying variables. For the first time, the classical theory of coupled circular waveguide modes for the description of the operating electromagnetic eigenmode in the helical interaction space is combined with a 3D PIC representation of the electron beam. This allows the simulation of the beamwave interaction over a broad bandwidth and at arbitrary harmonics of the cyclotron frequency. In addition, arbitrary electron beams (with spreads, offsets of the guiding center from the symmetry axis, etc.) can be investigated. The new approach is compared with the full-wave 3D PIC code CST Microwave Studio. A good agreement of the simulation results is achieved, while the computing time is significantly reduced.Index Terms-Gyrotron traveling wave tube (gyro-TWT), helically corrugated waveguide, coupled modes method, particle-in-cell (PIC).

Section: A W-band Helical Gyro-twtmentioning

confidence: 99%

Time-Domain Simulation of Helical Gyro-TWTs With Coupled Modes Method and 3-D Particle Beam

IEEE Trans. Electron Devices

Avramidis

Feuerstein

et al. 2022

“…This is of particular interest at sub-THz frequencies above 250 GHz where the magnetic field strength would exceed 10 T for a gyro-device operated at the fundamental cyclotron harmonic. However, the saturated gain of H-GTWTs usually does not exceed 30 dB because of parasitic reflection-induced oscillations [10]- [12].…”

Section: Introductionmentioning

confidence: 99%

New Type of Sub-THz Frequency-Doubling Gyro-TWT With Helically Corrugated Circuit

IEEE Electron Device Lett.

Feuerstein

Illy

et al. 2022

A novel type of frequency doubling gyrotron traveling wave amplifier (FD-GTWT) for applications that require high-power microwave in the sub-THz frequency range is presented. The proposed FD-GTWT delivers high power and high gain over a broad bandwidth and simultaneously doubling the frequency of the input signal. Simulations of a first 263 GHz FD-GTWT design are presented, which show for a 10 mW driving signal at 131.5 GHz an RF output power of 250 W at 263 GHz and a gain of >40 dB over a bandwidth of 17.5 GHz. The basis of the FD-GTWT are two interaction circuits separated by a long drift section. In the first circuit, the electron beam is pre-bunched at the fundamental cyclotron harmonic. In the second one, highpower RF is induced by the pre-bunched electron beam at the 2nd cyclotron harmonic. Both sections consist of helically corrugated waveguides that efficiently suppress parasitic interactions and allow broad bandwidth.

“…Particularly challenging is the demand for high bandwidth at high power. Promising technologies for both the amplifier and the absorber are gyrotron traveling-wave tubes (gyro-TWTs) with a helical interaction circuit [9], [10], [11]. This type of vacuum electron tubes provide a series of advantages compared to classical gyro-TWTs based on cylindrical interaction waveguides with dielectric losses [12], [13].…”

Section: Introductionmentioning

confidence: 99%

“…This type of vacuum electron tubes provide a series of advantages compared to classical gyro-TWTs based on cylindrical interaction waveguides with dielectric losses [12], [13]. The helical gyro-TWTs provide a larger bandwidth, are less prone to electron velocity spread and can operate at lower magnetic fields, since the electron-wave interaction takes place at the 2nd cyclotron harmonic [11]. This is of particular interest for the development of devices in the sub-THz range, where the required magnetic field strength for operation at the fundamental cyclotron harmonic can easily exceed 10 T.…”

Section: Introductionmentioning

confidence: 99%

Extended Feedback System for Coupled Sub-THz Gyro-Devices to Provide New Regimes of Operation

IEEE Trans. Electron Devices

Avramidis

Illy

et al. 2020

A new type of high-power pulsed source in the millimeter and sub-millimeter frequency range, utilizing the method of passive mode locking, was proposed in 2015 by the Institute of Applied Physics (IAP-RAS) in Nizhny Novgorod. This principle, well known from laser physics, allows the generation of a periodic series of powerful, coherent, ultra-short pulses. In the millimeter and sub-millimeter wavelength range this can be realized using an amplifier and a saturable absorber coupled in a feedback loop. For the coupling of the two devices, a sophisticated feedback system is required. Such a system, based on simple overmoded waveguide components, was previously proposed by the authors. The present article shows how the proposed feedback system can be extended, allowing for a wide range of possible operation regimes for two coupled gyro-devices. Particularly noteworthy is the application of the modified feedback system for the realization of a two-stage amplifier in the sub-THz range. Furthermore, it seems to be possible to use two helical gyrodevices coupled in the proposed way as a source of coherent pulses, as a free-running or locked CW source, and as a twostage amplifier. In all cases, no design changes of the feedback system are required. Index Terms-sub-THz, high power, ultra-short pulses, passive mode locking, feedback system, quasi-optical.