DFG-RSF: Generation of Ultrashort Pulses in Millimeter and Submillimeter Bands for Spectroscopy and Diagnostic of Various Media Based on Passive Mode-locking in Electronic Devices with Nonlinear Cyclotron Absorber in the Feedback Loop.
Final Report Abstract
In this project the research and development of a novel (in the field of microwave engineering) RF system for the generation of ultra-short, high-power, broadband, coherent signals was investigated. For that, a new mechanism for generation of ultra-short pulses based on two broadband gyro-devices coupled in a feedback loop was used. RF systems which are capable to generate ultra-short pulses coherently, and, at the same time, which achieve a reasonable RF output power of more than a few Watts in the millimeter and submillimeter (sub-THz) frequency bands are gaining fundamental interest in the research community. Those RF systems might become the key components of possible future THz diagnostics systems. Two examples are the diagnostics of dense plasmas and the DNP-NMR spectroscopy. In both cases, powerful RF sources which are generating ultra-short coherent pulses in the millimeter and sub-millimeter frequency range would enable the community to develop new devices with performance improvements in the areas of sensitivity, resolution and data acquisition speed. The generation of ultra-short pulses based on passive mode locking together with a non-linear saturable absorber in the feedback loop is well known from laser physics. The application of this method to the millimeter and sub-THz frequency bands and for high-power at the same time require a combination of innovative high-power broadband vacuum electronics amplifiers and novel non-linear vacuum electronics absorbers coupled by a new quasi-optical feedback system. All three key components must have a sufficient bandwidth to allow the generation of the ultra-short pulses. The fundamental idea bases on the passive mode locking in lasers. Hence, the amplifier will take the part of the active laser medium. The non-linear saturable absorber in the feedback loop attenuates weak signals while high power signals pass practically without attenuation. In the project, theoretical analyses were performed to achieve a fundamental physical understanding and to identify suited technologies for a realization of the proposed source of coherent pulsed signals. Based on the theoretical models, a first experimental realization of the proposed concept was prepared. An important result of the project is the development of the required tools to analyze and simulate the critical elements of the amplifier, the non-linear saturable absorber and the quasioptical feedback system. Different simulation tools were developed and used for the study of physical effects and the development of the key components. The semi-analytical model developed from the IAP-RAS allows a fundamental physical understanding of the problem and fast simulations of the dominant interactions in the pulsed generator. Developed extensions for the simulation tool PICLas, originally developed by the IAG, University Stuttgart for the simulation of 3D plasma currents, allow accurate, full-wave PIC simulations of the vacuum devices. For the simulation of the “cold” structures, a simulation tool (KarLESSS) based on an electricfield-integral-equation solver was developed. With KarLESSS, full-wave simulations of all cold structures could be performed, namely, the simulation of the dispersion relation of the helicallycorrugated structures, full wave simulation of all passive components such as polarizers and horn antennas and the quasi-optical feedback system. It was decided to realize a first proof-of-concept experiment at 34 GHz in the RAS-IAP. Based on the developed physical model and by re-using of the existing equipment, for the first time a pulsed generator in the millimeter frequency range based on the mechanism of passive mode locking was developed and is currently under production at the RAS-IAP. In addition to the 34 GHz proof-of-concept experiment, first investigations in components for a pulsed generator at 263 GHz are performed. In particular, a novel design optimized for feedback systems at sub-THz frequencies was developed.
Publications
- (2017). Generation of trains of ultrashort microwave pulses by two coupled helical gyro-TWTs operating in regimes of amplification and nonlinear absorption. Physics of Plasmas, 24(2), 023103
Ginzburg, N. S., Denisov, G. G., Vilkov, M. N., Sergeev, A. S., Zotova, I. V., Samsonov, S. V., and Mishakin, S. V.
(See online at https://doi.org/10.1063/1.4975084) - (2017). Simulation of electromagnetic fields scattered from arbitrary shaped electric conductors. In EPJ Web of Conferences (Vol. 149, p. 04016). EDP Sciences
Marek, A., Avramidis, K. A., Copplestone, S. M., Ginzburg, N. S., Illy, S., Jelonnek, J., Jin, J., Mishakin, S. V., Müller, A.-S., Ortwein, P.and Thumm, M.
(See online at https://doi.org/10.1051/epjconf/201714904016) - (2017, October). Passive mode-locking and generation of ultrashort pulses in electron oscillators with saturable absorber in the feedback loop. In 2017 47th European Microwave Conference (EuMC) (pp. 684-686). IEEE
Ginzburg, N., Denisov, G., Vilkov, M., Zotova, I., Sergeev, A., Samsonov, S., Mishakin, S., Kocharovskaya, E., Jelonnek, J., and Marek, A.
(See online at https://doi.org/10.23919/EuMC.2017.8230939) - (2018). Contributions to the Joint DFG-RSF Project-Generation of Ultra-Short Microwave Pulses. In EPJ Web of Conferences (Vol. 187, p. 01027). EDP Sciences
Marek, A., Avramidis, K. A., Copplestone, S. M., Ginzburg, N. S., Illy, S., Jelonnek, J., Jin, J., Mishakin, S. V., Ortwein, P., and Thumm, M.
(See online at https://doi.org/10.1051/epjconf/201818701027) - (2018). PIC Simulations of Ka-band Ultra-Short Pulse Oscillator with Resonance Cyclotron Absorber in the Feedback Loop. In EPJ Web of Conferences (Vol. 187, p. 01021). EDP Sciences
Ginzburg, N. S., Denisov, G. G., Vilkov, M. N., Zotova, I. V., Sergeev, A. S., Samsonov, S. V., Marek, A., and Jelonnek, J.
(See online at https://doi.org/10.1051/epjconf/201818701021) - (2018). Ultrawideband Millimeter-Wave Oscillators Based on Two Coupled Gyro-TWTs With Helical Waveguide. IEEE Transactions on Electron Devices, 65(6), 2334-2339
Ginzburg, N. S., Denisov, G. G., Vilkov, M. N., Zotova, I. V., Sergeev, A. S., Rozental, R. M., Marek, A., and Jelonnek, J.
(See online at https://doi.org/10.1109/TED.2018.2801021) - (2018, March). Benefits of advanced full-wave vector analysis codes for the design of high-power microwave tubes. In Microwave Conference (GeMiC), 2018 11th German (pp. 279-282). IEEE
Marek, A., Avramidis, K. A., Ginzburg, N. S., Illy, S., Jelonnek, J., Jin, J., Mishakin, S. V., and Thumm, M.
(See online at https://doi.org/10.23919/GEMIC.2018.8335084)
