Abstract-Theoretical and Experimental Investigations of Terahertz-Range Gyrotrons with Frequency and Spectrum Control

G. G. Denisov, M. Y. Glyavin, A. E. Fedotov,  I. V. Zotova

https://link.springer.com/article/10.1007/s10762-020-00672-8

We present the results of recent IAP RAS investigations, which were aimed at controlling the radiation frequency and spectrum of THz-range medium-power gyrotrons. Problems of extending the smooth frequency tuning band and providing high-frequency stability in CW regimes are discussed. The development of gyrotrons with stated parameters are of interest for many modern applications, including DNP/NMR and RAD spectroscopy, direct measurements of positronium hyperfine structure, and diagnostic of various media.

Abstract- Time-Domain Multimode Analysis of a Terahertz Gyro-TWT Amplifier

 Chao-Hai Du, Shi Pan, Hui-Qi Bian, Pu-Kun Liu

http://ieeexplore.ieee.org/document/8306118/

 High-order mode employed as the operating mode of a terahertz (THz) gyrotron traveling-wave tube (gyro-TWT) amplifier shows strong dispersion, which deteriorates the device performance in amplifying picosecond THz pulses. Theoretical investigation of a THz gyro-TWT amplifier with a lossy cylindrical circuit is carried out to study the problems, such as lossy structure design, parameters selection, frequency-domain performance, and time-domain dynamics. The robust high growth rate low-kz amplification and the broadband high-kz amplification are two preferred operation conditions. The revealed characteristics are also useful for developing THz gyro-TWTs with other kinds of over-moded circuits

Abstract-Controllable Thermal-Frequency Tuning of a Terahertz Gyrotron

 Li Luo, Chao-Hai Du, Xiang-Bo Qi,  Zheng-Di Li, Shi Pan,  Ming-Guang Huang, Pu-Kun Liu

http://ieeexplore.ieee.org/document/8240959/

Gyrotron performance is sensitive to cavity structure parameters, and the cavity shape is temperature dependent due to thermal deformation induced by temperature rise from ohmic loss power on finite-conductivity cavity wall. Accordingly, this paper studies a frequency-tuning scheme for terahertz gyrotron by properly controlling the cavity thermal deformation. By combining gyrotron nonlinear theory and finite-element method software, controllable thermal-frequency-tuning capability of a continuous-wave 263-GHz gyrotron is systematically investigated, toward maintaining gyrotron operating under gyromonotron condition in frequency-tuning band, and achieving high efficiency in broadband frequency-tuning range. After studying cavity thermal distribution, structure deformation, and electron beam-wave interaction, an optimized cavity structure with transition sections on both ends is proposed. Simulation predicts that with the two-transition-section cavity, via additional thermal tuning, the continuous-frequency-tuning band is capable of reaching 1.75 GHz, which is 5 times of the initial bandwidth. Furthermore, using the thermal-frequency-tuning technology, impressive high efficiency above 17% is obtainable in the whole frequency-tuning range.

Abstract-Terahertz gyrotrons with quasi-regular cavities

 Ivan V. Osharin,  Ilya V. Bandurkin,  Yury K. Kalynov, Audrey V. Savilov

http://ieeexplore.ieee.org/document/8105117/

We describe two ways of the use in high-harmonic gyrotrons of quasi-regular cavities with short irregularities formed by the widening of cavity radius. The first one is a significant improvement of the selectivity of the second-harmonic gyrotrons due to the supression of parasitic near-cutoff fundamental-harmonic waves. The second approach is aimed to solve a typical problem of weakly-relativistic high-harmonics gyrotrons, namely, the use of long cavities ensuring extremely high diffraction Q-factors and a great share of Ohmic losses. We propose a quasi-regular cavity with periodic phase correctors, where a far-from-cutoff axial mode with a decreased diffraction Q-factor is excited in a gyrotron-like regime.

Abstract-Gyrotrons for High-Power Terahertz Science and Technology at FIR UF

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  Toshitaka Idehara, Svilen Petrov Sabchevsk
  http://link.springer.com/article/10.1007/s10762-016-0314-5
  In this review paper, we present the recent progress in the development of a series of gyrotrons at the Research Center for Development of Far-Infrared Region, University of Fukui, that have opened the road to many novel applications in the high-power terahertz science and technology. The current status of the research in this actively developing field is illustrated by the most representative examples in which the developed gyrotrons are used as powerful and frequency-tunable sources of coherent radiation operating in a continuous-wave regime. Among them are high-precision spectroscopic techniques (most notably dynamic nuclear polarization-nuclear magnetic resonance, electron spin resonance, X-ray detected magnetic resonance, and studies of the hyperfine splitting of the energy levels of positronium), treatment and characterization of advanced materials, and new medical technologies.

Abstract-Gyrotrons for High-Power Terahertz Science and Technology at FIR UF

Toshitaka Idehara, Svilen Petrov Sabchevski

(Submitted on 18 Jul 2016)

https://arxiv.org/abs/1607.04964

In this paper, we present the recent progress in the development of a series of gyrotrons at FIR UF that have opened the road to many novel applications in the high-power Terahertz science and technology. The current status of the research in this actively developing field is illustrated by the most representative examples in which the developed gyrotrons are used as powerful and frequency tunable sources of coherent radiation operating in a CW regime. Among them are high-precision spectroscopic techniques (most notably DNP-NMR, ESR, XDMR, and studies of the hyperfine splitting of the energy levels of positronium), treatment and characterization of advanced materials, new medical technologies.

Abstract-Study on calculation method of terahertz gyrotron with special cross-section cavity

Xuesong Yuan ; Terahertz S&T Res. Center, Univ. of Electron. Sci. & Technol. of China, Chengdu, China ; Yu Han ; Yang Yan

http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=6092205

In order to develop high power terahertz sources, high harmonic terahertz gyrotrons with special cross-section cavity have been proposed. The calculation method of the gyrotrons mentioned above has been investigated based on the three-dimensional electromagnetic simulation software CST and traditional nonlinear theory of gyrotrons in this paper. In this method the analytical solution of the high frequency fields is replaced by inserting the simulation results of CST, the beam-wave interaction efficiency, coupling coefficient and starting current have been obtained. A 0.4THz third harmonic TE33 mode gyrotron with corrugated interaction cavity has been designed by making use of this calculation method.