Laboratory of High-Current and Microwave Electronics

The laboratory conducts interdisciplinary work at the intersection of vacuum electronics, plasma physics and materials science, responding to key challenges of modern science and technology — from future energy to high-tech medicine.

1. High-power gyrotrons of millimeter and submillimeter ranges. Generation of high-power microwave radiation for controlled thermonuclear fusion (CTF).

The work is aimed at increasing the efficiency and stability of megawatt-level power gyrotrons necessary for plasma heating and non-inductive current drive in tokamaks and stellarators. Design improvements directly influence the advent of the era of clean thermonuclear energy.

2. Physics of intense electron flows. Controlling space charge dynamics in strong electromagnetic fields

Collective processes, parasitic oscillations and the influence of inhomogeneous fields on the quality of electron beam transport are investigated. Understanding these mechanisms is necessary for creating reliable and efficient sources of terahertz and sub-terahertz radiation.

3. Emission electronics and new materials. Creation of cold field emitters based on nanostructures and composites.

Durable electron sources that do not require heating are being developed using structured coatings and carbon nanomaterials. This direction is relevant for miniaturization and increasing the service life of vacuum electronics devices, including space engines, portable X-ray sources, and microwave electronics.

4. Electron-optical systems of a new type. Formation of high-quality helical electron beams (HEBs).

Development of methods for calculating and experimentally implementing electron guns with a high degree of beam laminarity. The relevance is dictated by the demand for increasing output power and expanding the frequency range of gyrotrons, including for advanced medical and spectroscopic applications.

5. Broadband crossed-field microwave devices. Generation of powerful quasi-noise signals and improvement of amplitrons.

Research is aimed at creating radiation sources with unique spectral characteristics for electronic warfare, telecommunications and information security systems. The use of new cathode materials makes it possible to solve the problems of increasing the duration and stability of generated pulses.

6. Interaction of high-power microwave radiation and electron beams with matter. Development of plasma and beam technologies for material processing.

Research results are used to develop methods for ultra-clean processing and surface modification, as well as for technologies for fuel injection into plasma (including ablation acceleration of macro-particles-pellets) in the interests of CTF and new industrial processes.

The scientific team has a comprehensive experimental and technological base necessary to perform all stages of the project. The available equipment allows for a full cycle of research — from the creation and comprehensive characterization of field emitters to testing finished microwave devices under operating conditions. In particular, the laboratory has:

1. Microwave devices and installations of the sub-terahertz range:

• A 140 GHz gyrotron mock-up, previously developed and tested by the team. It provides the ability to test new architectures of electron-optical systems and integrate field emitters in the sub-terahertz range.
• Experimental SPbPU 74 GHz gyrotron, equipped with systems for measuring and monitoring output characteristics. The apparatus is equipped with original methods for analyzing the spatial and energy parameters of helical electron beams (HEBs), as well as diagnostics of collective processes in the beam plasma.

2. Equipment for research and modification of emitters:

• Automated installation for characterizing emission properties, allowing real-time recording of current-voltage characteristics, analysis of emission current stability and durability of cathodes under high and ultrahigh vacuum conditions.
• High-resolution scanning probe microscopes (STM and AFM), providing nanometer control of surface morphology, measurement of local work function and assessment of emission uniformity of multi-tip structures.
• Magnetron sputtering installation, designed for applying functional coatings (including metal-fullerene and multilayer nanostructured compositions) to complex-profile emitting structures with controlled uniformity and high adhesion.

3. Stands for research of electron-optical systems (EOS):

• Automated stand for electron gun research, allowing laboratory measurements of velocity spread, transverse beam uniformity and its emittance. The stand provides long-term life tests of cathode-grid assemblies, equipped with high-voltage sources and precision current recording systems.

4. Technological infrastructure for assembly and experiments:

• A fleet of high and ultrahigh vacuum stations.
• High-voltage power supplies for powering microwave devices.
• Electron beam diagnostic systems (including transverse structure analyzers).
• Precision equipment for assembly, alignment and adjustment of electron-optical and electrodynamic systems in clean conditions.

Publications can be viewed by following the links below:

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As part of the conducted research, a set of fundamental and applied works was performed aimed at the creation and optimization of electron-optical systems (EOS) with cold field emitters for use in sub-terahertz gyrotrons. The results obtained lay the foundation for a new generation of compact and energy-efficient sources of powerful coherent radiation.

1. A number of promising field emitters with unique properties have been created and experimentally studied.

Systematic work was carried out on the synthesis, development and comprehensive testing of field cathodes of various types and morphologies, which made it possible to establish the relationship between their structure and emission characteristics:

Multi-tip emitters with metal-fullerene protective coatings: Emitters with nanostructured coatings have been studied, which will increase the conductivity and strength of the tips while simultaneously minimizing the impact of ion bombardment under technical vacuum conditions [Sominskii G. Formation of an Annular Electron Beam for Subterahertz Gyrotrons Using an Electron-Optical System with a Multitip Field Emitter / G. Sominskii, E. Taradaev, S. Taradaev, M. Glyavin, A. Zuev // IEEE Transactions on Electron Devices. – 2024. – Vol. 71, No. 11. – P. 7056–7060; Taradaev E. Characteristics of an Annular Electron Flow Formed by an Electron Gun with a Field Emitter / E. Taradaev, G. Sominskii // IEEE Transactions on Electron Devices. – 2022. – Vol. 69, No. 5. – P. 2675–2679; Taradaev E. The Influence of the Tips Geometry on the Formation of Electron Velocities in the Electron Flow / E. Taradaev, S. Taradaev, G. Sominskii // Proceedings of the 2024 International Conference on Electrical Engineering and Photonics (EExPolytech). – Saint Petersburg, 2024. – P. 371–374].

Multilayer and composite field emitters: Emitters constructed from materials with different work functions have been developed and tested. This made it possible to purposefully control the distribution of the electric field on the cathode surface.

Composite emitters based on carbon materials: For the first time, cathodes based on thermally expanded graphite (TEG) and its mixtures with diamond granules were synthesized and studied. The unique microstructure of TEG, combining a high density of emission centers with the high thermal conductivity of diamond inclusions, made it possible to obtain stable field emission at high current densities [Taradaev E. P. Formation of an electron flow by an electron-optical system with a composite field emitter made of thermally expanded graphite and a mixture of thermally expanded graphite with diamond granules / E. P. Taradaev, G. G. Sominsky, S. P. Taradaev, S. K. Gordeev // Scientific and Technical Bulletin of St. Petersburg State Polytechnic University. Physical and Mathematical Sciences. – 2025. – Vol. 18, No. 1. – P. 103–110; Gordeev S. Electron Flows Formed by Electron-Optical Systems Using Composite Field Emitters Made of Thermally Expanded Graphite and Diamond–Graphite Mixtures / S. Gordeev, V. Sezonov, G. Sominskii, E. Taradaev, S. Taradaev // IEEE Transactions on Electron Devices. – 2023. – Vol. 70, No. 10. – P. 5348–5352; Egorova A. V. Study of the characteristics of electron flows formed by an electron-optical system with a field emitter made of thermally expanded graphite / A. V. Egorova, E. P. Taradaev, S. P. Taradaev, G. G. Sominsky // Week of Science of IET: materials of the All-Russian conference. – Saint Petersburg, 2024. – P. 182–185].

2. A set of original methods for diagnosing electron beams has been developed and implemented [Taradaev E. Characteristics of an Annular Electron Flow Formed by an Electron Gun with a Field Emitter / E. Taradaev, G. Sominskii // IEEE Transactions on Electron Devices. – 2022. – Vol. 69, No. 5. – P. 2675–2679; Taradaev E. Calculation of the Characteristics of the Electron Beam Formed by an Electron-Optical System with a Multi-Tip Field Emitter / E. Taradaev, G. Sominskii // 2021 22nd International Vacuum Electronics Conference (IVEC 2021). – 2021. – pp 1-2; Egorova A. V. Study of the characteristics of electron flows formed by an electron-optical system with a field emitter made of thermally expanded graphite / A. V. Egorova, E. P. Taradaev, S. P. Taradaev, G. G. Sominsky // Week of Science of IET: materials of the All-Russian conference. – Saint Petersburg, 2024. – P. 182–185].

To diagnose and determine the parameters of the generated electron flows, specialized diagnostic equipment and software have been created and tested:

Spatiotemporal diagnostics: A methodology for analyzing the spatial current density distribution in an electron beam using phosphor analyzers has been implemented, making it possible to visualize the beam shape (in particular, to obtain the annular beam required for a gyrotron) and study its spatial homogeneity.

Energy diagnostics: Precision measurements of the electron energy spectrum in the beam have been carried out using retarding field energy analyzers. A special methodological achievement is the ability to carry out such measurements not only in stationary mode, but also in the mode of single microsecond pulses, which makes it possible to study dynamic processes in the EOS.

Computer modeling [Taradaev E. Study of the Possibility of Reducing the Velocity Spread in the Electron Flow Formed by an Electron-Optical System with a Multi-Tip Field Emitter / E. Taradaev, G. Sominskii // 2021 46th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz). – 2021. – pp. 1-2; Taradaev E. Calculation of the Characteristics of the Electron Beam Formed by an Electron-Optical System with a Multi-Tip Field Emitter / E. Taradaev, G. Sominskii // 2021 22nd International Vacuum Electronics Conference (IVEC 2021). – 2021. – pp 1-2.]: A specialized software package has been developed for self-consistent calculation of electrostatic fields, electron trajectories and emission characteristics of cathodes. The modeling made it possible to optimize the EOS geometry and predict such key parameters as perveance and velocity spread, followed by experimental verification.

3. A full-functional mock-up of a gyrotron with an operating frequency of 140 GHz has been designed, manufactured and tested [Sominskii G. Formation of an Annular Electron Beam for Subterahertz Gyrotrons Using an Electron-Optical System with a Multitip Field Emitter / G. Sominskii, E. Taradaev, S. Taradaev, M. Glyavin, A. Zuev // IEEE Transactions on Electron Devices. – 2024. – Vol. 71, No. 11. – P. 7056–7060; Taradaev E. P. Current and velocity characteristics of electron flows formed by an electron-optical system with a multi-tip field emitter / E. P. Taradaev, G. G. Sominsky, S. P. Taradaev // Scientific and Technical Bulletin of St. Petersburg State Polytechnic University. Physical and Mathematical Sciences. – 2024. – Vol. 17, No. 1. – P. 64–70].

Based on the obtained fundamental results, a transition to applied implementation was carried out:

The design of all key components of the mock-up has been developed, including an electron-optical system based on a multi-tip field emitter, a magnetic field generation system and a gyrotron resonator.

The mock-up was assembled and comprehensively tested. During test runs, the operating characteristics of the generated electron flow (current, shape, perveance) were determined and its suitability for exciting electromagnetic oscillations in a given frequency range was confirmed.

4. The fundamental possibility of generating a gyrotron with a multi-tip field emitter has been experimentally confirmed [Taradaev S. P. Development of an electron-optical system with a field emitter for use in a 140 GHz gyrotron / S. P. Taradaev, E. P. Taradaev, G. G. Sominsky // Electronics and Microwave Microelectronics. – 2025. – Vol. 1, No. 1. – P. 200–204; G. Sominskii, E. Taradaev, S. Taradaev, M. Glyavin, A. Zuev, Experimental Study of a Gyrotron with a Multi-Tip Cold Field Emitter// IEEE TED (in press) doi:10.1109/TED.2025.3631457].

The most significant applied result is the demonstration of radiation generation mode at a frequency of 140 GHz under laboratory conditions. This result is direct experimental proof of the operability and promise of the entire developed concept of using field emitters in gyrotrons.

The completed cycle of research not only solved a number of specific scientific and technical problems, but also formed an extensive program for further research. The obtained results open up wide opportunities for optimizing emitter materials, creating EOS for gyrotrons of higher frequency ranges (up to terahertz), as well as for developing compact and economical gyrotrons with a long service life, demanded in diagnostic systems for thermonuclear plasma and medicine.

The laboratory maintains close scientific ties with leading world centers of gyrotron electronics. Ongoing collaboration is carried out with the Nizhny Novgorod Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) — the leading organization for high-power microwave devices in Russia. At the international level, long-term partnerships are maintained with the Karlsruhe Institute of Technology (KIT, Germany) — one of the main European developers of gyrotron systems for CTF.