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                  International Journal of Terahertz Science and Technology
Vol.9, No.4, December 2016. PP.117-186 (6)--Focus Issue on applications-oriented gyrotrons (Part I)
date£º2016-12-31 21:25:52 Click No.£º1203

Preface

Gyrotrons are finding more and more applications, especially in recent years. Numerous gyrotron-based DNP/NMR systems and MW-level gyrotrons for plasma heating in record-breaking fusion devices testify to it. To name one other example, a W-band gyro-TWT has been operational since 2014 to power the world's largest radome-enclosed antenna for the Haystack radar. The International Journal of Terahertz Science and Technology (TST) is very pleased to highlight some of the latest progresses made on applications-oriented gyrotrons in this focus issue.

First of all, as the guest editor, I am grateful to the host institute of TST, the University of Science and Technology of China, for contributing two excellent papers entitled ¡°Continuously frequency-tunable 0.22 THz gyrotron oscillator with quasi-optical resonator¡± and ¡°The theoretical investigation and design on 0.42 THz gyrotron with complex cavity¡±. They have each investigated a novel interaction structure, which enables stable THz wave generation at power levels of tens of kW.

The paper entitled ¡°Modulation and stabilization of the output power and frequency of FU series gyrotrons¡± came from the group who pioneered THz gyrotrons decades ago and has been as dynamic as ever. It is a paper impressively rich in physics, technology, and applications.

The paper entitled ¡°Design and experimental study of a high power 140 GHz, TE22.6 mode gyrotron for EAST¡± is the first journal documentation of a new (perhaps the first) series of fusion gyrotron research in China. It is a respectable endeavor aimed at plasma heating for the Experimental Advanced Superconducting Tokamak (EAST).

The paper entitled ¡°Study on W-band TE02gyro-TWT¡± gives an informative overview and recent progress on the gyro-TWT research in China, one the most active and productive countries on this important topic.

Last but not least, the paper entitled ¡°Development of high-frequency CW gyrotrons for DNP/NMR applications¡± came from the group who has produced the vast majority of THz gyrotrons (over 30 so far) for DNP/NMR systems around the world. We are particularly pleased that they have decided to present their first journal paper on this fantastic accomplishment in TST, and share with us some beautiful pictures.

More papers will be added to this issue after some invited authors take a well-deserved break for a happy holiday season.

Kwo Ray Chu

Guest Editor

December 31, 2016


TST, Vol. 9, No. 4, PP. 117-130

(Invited Review Paper) Modulation and Stabilization of the Output Power and Frequency of FU Series Gyrotrons

T. Idehara 1*, E.M. Khutoryan 1, 2, I. Ogawa 1, Y. Matsuki 3 and T. Fujiwara 3
1 Research Center for Development of Far-Infrared Region, University of Fukui (FIR UF), Bunkyo 3-9-1, Fukui-shi, Fukui-ken 910-8507, Japan
2 O. Ya.Usikov Institute for Radiophysics and Electronics IRE NASU, 12, Proskura str., Kharkiv 61085, Ukraine
3 Institute of Protein Research, Osaka University, Yamada-oka 3-2, Suita-shi, Osaka-fu 565-0871, Japan
* Email:
idehara@fir.u-fukui.ac.jp

(Received 22 December 2016)

Abstract: Both the modulation and the stabilization of the output power and frequency are very important for many applications of gyrotrons. In this paper we present the review of recent progress in the fast modulation and stabilization of the output power and frequency of the gyrotrons developed at FIR UF.

Keywords: Gyrotron, Power and frequency modulation, Power and frequency stabilization

doi: 10.11906/TST.117-130.2016.12.12

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TST, Vol. 9, No. 4, PP. 131-140

(Invited paper) Design and experimental study of a high power 140 GHz, TE22.6 mode gyrotron for EAST

Bentian Liu *, JinjunFeng, Zhiliang Li, Yang Zhang, Efeng Wang, and BoyangTian
National Key Laboratory of science and technology on Vacuum Electronics, Beijing Vacuum Electronics Research Institute, Beijing, China.
* Email:
liubentian@hotmail.com

(Received 22 December 2016)

Abstract: The parameters of a 140GHz TE22.6- mode gyrotron are presented in the article. A single-anode magnetron injection gun (MIG) and the cylindrical resonant cavity operating in the TE22.6- mode are designed for the 140GHz gyrotron with output power at axial direction. The theoretical efficiency of the gyrotron with operating voltage 80kV, electron current 40A is about 42%. The gyrotron has been fabricated and tested. In short pulse operation (~70 microseconds) an output power of ~150kW with frequency of 140.36GHz is obtained in operating voltage 70kV, electron beam 20A.

Keywords: Gyrotron, High power, ECRH, EAST, Nuclear Fusion, ITER.

doi: 10.11906/TST.131-140.2016.12.13

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TST, Vol. 9, No. 4, PP. 141-148

(Invited paper) A Study of W-band TE02 mode gyro-TWT

Xu Zeng *, EFeng Wang, Jinjun Feng
National Key Laboratory of Science and Technology on Vacuum Electronics, Beijing Vacuum Electronics Research Institute, Post Box 749-41, 100015, Beijing, China,
* Email:
zengxu1108@163.com

(Received 22 December 2016)

Abstract: In order to increase the electron beam transmission, a W-band TE02 mode gyro-TWT with a periodic dielectric loaded interaction circuit has been studied and the main parameters have been presented in the paper. The simulation results show that the W-band TE02 mode gyro-TWT is predicted to yield a peak output power of above 160kW with the bandwidth of 8GHz, and saturated gain above 49 dB at the interaction efficiency above 20%.

Keywords: W-band, Gyro-TWT, TE02 mode, Periodic dielectric loaded circuit, Electron flow rate

doi: 10.11906/TST.141-148.2016.12.14

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TST, Vol. 9, No. 4, PP. 149-165

(Invited paper) The theoretical investigation and design on 0.42 THz gyrotron with complex cavity

Sheng Yu *, Qixiang Zhao, Tianzhong Zhang, Youwei Yang, Yanyan Zhang, and Zhipeng Wang
Terahertz Science and Technology Research Center, University of Electronic Science and Technology of China, Chengdu, 610054, China
* Email:
yush@uestc.edu.cn

(Received 21 December 2016)

Abstract: The research on terahertz science and technology are being intensified due to enormous potential in the field of high-density plasma diagnostics and nuclear magnetic resonance (NMR). However, the lack of terahertz source especially high power terahertz source is a main obstacle. Gyrotron, based on the ECRMs (Electron Cyclotron Resonance Masers), is one of the most promising sources to generate high power terahertz radiation. Therefore, a 0.42 THz gyrotron operating at second harmonic is designed and analyzed in this paper. To alleviate the mode competition, a gradually tapered complex cavity is adopted, where the pair of operating modes is TE17.3/TE17.4. a candidate operating point is selected by linear and nonlinear theoretical analysis, with 50 kV beam voltage, 6 A beam current and 8.03 T magnetic field, the output power and interaction efficiency can reach about 78.48 kW and 26.16%, respectively. The mode competition in the designed gyrotron is also investigated with the time-dependent multi-mode nonlinear code. The results show that the operating mode can be prior excited and other competing modes are effectively suppressed. A double anode magnetron injection gun (MIG) with 3.19% maximum transverse velocity spread is also designed and simulated to satisfy the requirement of the proposed gyrotron. These simulation results can provide the theoretical basis for the 0.42 THz gyrotron experiments.

Key Word: Terahertz, Gyrotron, Complex cavity.

doi: 10.11906/TST.149-165.2016.12.15

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TST, Vol. 9, No. 4, PP. 166-176

(Invited paper) Continuously frequency-tunable 0.22 THz gyrotron oscillator with quasi-optical resonator

Xiaotong Guan *, Wenjie Fu, and Yang Yan
Terahertz Research Center, University of Electronic Science and Technology of China, Chengdu, 610054 China
* Email:
heartsacegxt@gmail.com

(Received 13 December 2016)

Abstract: A 0.22 THz continuously frequency-tunable gyrotron oscillator with quasi-optical resonator has been investigated in this paper. The operating frequency is changed by mechanically adjusting the mirror separation. The simulation results have demonstrated that an 11.7 GHz bandwidth of frequency tuning and output power of 38 kW could be achieved.

Keywords: Cylindrical confocal waveguide, Frequency tunable, Quasi-optical resonator, THz gyrotron

doi: 10.11906/TST.166-176.2016.12.16

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TST, Vol. 9, No. 4, PP. 177-186

(Invited paper) Development of high-frequency cw gyrotrons for DNP/NMR applications

Monica Blank 1*, Philipp Borchard 1, Stephen Cauffman 1, Kevin Felch 1, Melanie Rosay 2 , and Leo Tometich 2
1
Communications and Power Industries, 811 Hansen Way, Palo Alto, CA 94304, USA
2 Bruker-Biospin, 15 Fortune Drive, Billerica, MA 01730, USA
* Email:
monica.blank@cpii.com

(Received 22 December 2016)

Abstract: Dynamic nuclear polarization (DNP) enhanced nuclear magnetic resonance (NMR) spectroscopy is an emerging and growing application for high-frequency, continuous-wave (cw) gyrotrons. For DNP, gyrotrons capable of producing tens to hundreds of watts at millimeter-wave and terahertz frequencies are required. As an original equipment manufacturer of gyrotrons for Bruker Biospin DNP/NMR spectrometers, CPI has developed cw gyrotrons at 263GHz, 395GHz, and 527GHz, all of which are capable of producing at least 50 W output power. The gyrotrons at all three frequencies operate at the second harmonic of the cyclotron frequency and produce high-quality Gaussian output beams suitable for transmission in corrugated waveguides. To date, 30 Bruker DNP/NMR systems using CPI gyrotrons have been installed around the world. Key features of the gyrotrons, as well as the results of experimental demonstrations, are presented.

Keywords: gyrotron, millimeter wave, terahertz, DNP, NMR spectroscopy

doi: 10.11906/TST.177-186.2016.12.17

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