Editorial

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2 pages, 133 KiB

Open AccessEditorial

High-Power Vacuum Electronic Devices from Microwave to THz Band: Way Forward

by Glyavin Mikhail

Electronics 2021, 10(19), 2436; https://doi.org/10.3390/electronics10192436 - 08 Oct 2021

Cited by 4 | Viewed by 1435

Abstract

It is generally accepted that the 20th century was the age of electronics [...] Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

Research

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9 pages, 25988 KiB

Open AccessArticle

Study of 3D-Printed Dielectric Barrier Windows for Microwave Applications

by Mikhail D. Proyavin, Dmitry I. Sobolev, Vladimir V. Parshin, Vladimir I. Belousov, Sergey V. Mishakin and Mikhail Y. Glyavin

Electronics 2021, 10(18), 2225; https://doi.org/10.3390/electronics10182225 - 10 Sep 2021

Cited by 4 | Viewed by 1674

Abstract

3D printing technologies offer significant advantages over conventional manufacturing technologies for objects with complicated shapes. This technology provides the potential to easily manufacture barrier windows with a low reflection in a wide frequency band. Several 3D printing methods were examined for this purpose, [...] Read more.

3D printing technologies offer significant advantages over conventional manufacturing technologies for objects with complicated shapes. This technology provides the potential to easily manufacture barrier windows with a low reflection in a wide frequency band. Several 3D printing methods were examined for this purpose, and the dielectric properties of the various types of materials used for 3D printing were experimentally studied in the frequency range 26–190 GHz. These measurements show that the styrene-butadiene-styrene and polyamide plastics are suitable for broadband low-reflection windows for low-to-medium-power microwave applications. Two barrier windows with optimized surface shapes were printed and tested. Results demonstrate that the studied technique can fabricate windows with a reflection level below −18 dB in the frequency band up to 160 GHz. Studied windows can be used for spectroscopic tasks and other wideband microwave applications. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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14 pages, 5235 KiB

Open AccessEditor’s ChoiceArticle

Design and Preliminary Experiment of W-Band Broadband TE₀₂ Mode Gyro-TWT

by Xu Zeng, Chaohai Du, An Li, Shang Gao, Zheyuan Wang, Yichi Zhang, Zhangxiong Zi and Jinjun Feng

Electronics 2021, 10(16), 1950; https://doi.org/10.3390/electronics10161950 - 13 Aug 2021

Cited by 15 | Viewed by 2069

Abstract

The gyrotron travelling wave tube (gyro-TWT) is an ideal high-power, broadband vacuum electron amplifier in millimeter and sub-millimeter wave bands. It can be applied as the source of the imaging radar to improve the resolution and operating range. To satisfy the requirements of [...] Read more.

The gyrotron travelling wave tube (gyro-TWT) is an ideal high-power, broadband vacuum electron amplifier in millimeter and sub-millimeter wave bands. It can be applied as the source of the imaging radar to improve the resolution and operating range. To satisfy the requirements of the W-band high-resolution imaging radar, the design and the experimentation of the W-band broadband TE₀₂ mode gyro-TWT were carried out. In this paper, the designs of the key components of the vacuum tube are introduced, including the interaction area, electron optical system, and transmission system. The experimental results show that when the duty ratio is 1%, the output power is above 60 kW with a bandwidth of 8 GHz, and the saturated gain is above 32 dB. In addition, parasitic mode oscillations were observed in the experiment, which limited the increase in duty ratio and caused the measured gains to be much lower than the simulation results. For this phenomenon, the reasons and the suppression methods are under study. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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15 pages, 7432 KiB

Open AccessArticle

Dependence of Irradiated High-Power Electromagnetic Waves on the Failure Threshold Time of Semiconductors Using a Closed Waveguide

by Sun-Hong Min, Jung-Il Kim, Matlabjon Sattorov, Seontae Kim, Dongpyo Hong, Seonmyeong Kim, Bong-Hwan Hong, Chawon Park, Sukhwal Ma, Minho Kim, Kyo-Chul Lee, Yong-Jin Lee, Han-Byul Kwon, Young-Joon Yoo, Sang-Yoon Park and Gun-Sik Park

Electronics 2021, 10(16), 1884; https://doi.org/10.3390/electronics10161884 - 06 Aug 2021

Viewed by 1881

Abstract

The failure threshold time of semiconductors caused by the impact of irradiated high-power electromagnetic waves (HPEM) is experimentally studied. A SN7442 integrated circuit (IC) is placed in an emulator with a WR430 closed waveguide and is irradiated by HPEM generated from a magnetron [...] Read more.

The failure threshold time of semiconductors caused by the impact of irradiated high-power electromagnetic waves (HPEM) is experimentally studied. A SN7442 integrated circuit (IC) is placed in an emulator with a WR430 closed waveguide and is irradiated by HPEM generated from a magnetron oscillator. The state of the SN7442 component is observed by a light-emitting diode (LED) detector and the voltage measured in the SN7442 component. As the magnitude of the electric field in the HPEM is varied from 24 kV/m to 36 kV/m, the failure threshold time falls from 195 s to 17 s with dependence of the irradiated electric field (E) on the failure threshold time (T) from T~E⁻¹² to a T~E⁻⁶. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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11 pages, 4232 KiB

Open AccessArticle

Experimental Investigation into the Optimum Position of a Ring Reflector for an Axial Virtual Cathode Oscillator

by Se-Hoon Kim, Chang-Jin Lee, Wan-Il Kim and Kwang-Cheol Ko

Electronics 2021, 10(16), 1878; https://doi.org/10.3390/electronics10161878 - 05 Aug 2021

Cited by 6 | Viewed by 1981

Abstract

A ring reflector was experimentally investigated using an axial virtual cathode oscillator (vircator). The ring reflector was installed behind the mesh anode of the axial vircator to enhance the microwave power output by forming a resonant cavity and increasing the electron beam to [...] Read more.

A ring reflector was experimentally investigated using an axial virtual cathode oscillator (vircator). The ring reflector was installed behind the mesh anode of the axial vircator to enhance the microwave power output by forming a resonant cavity and increasing the electron beam to microwave energy conversion efficiency. The optimum position of the ring reflector is analyzed through simulations and experiments by varying the anode to reflector distance from 6 mm to 24 mm in 3 mm steps. PIC simulations show that the ring reflector enhances the microwave power of the axial vircator up to 220%. Experiments show that the microwave power from the axial vircator without the ring reflector is 11.22 MW. The maximum average peak microwave power of the axial vircator with the ring reflector is 25.82 MW when the anode to ring reflector distance is 18 mm. From the simulations and experiments, it can be seen that the ring reflector yields decaying enhancement that is inversely proportional to the anode to ring reflector distance and there is no noticeable microwave enhancement after 24 mm. The frequency range attained from the simulations and experiments is 5.8 to 6.7 GHz and 5.16 to 5.8 GHz, respectively. The difference between the simulation and experimental results is due to the error in the anode to cathode gap distance. Although the frequency is slightly changed, the ring reflector seems to have no influence on the frequency of the generated microwave. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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11 pages, 3541 KiB

Open AccessArticle

Over-Size Pill-Box Window for Sub-Terahertz Vacuum Electronic Devices

by Tongbin Yang, Xiaotong Guan, Wenjie Fu, Dun Lu, Chaoyang Zhang, Jie Xie, Xuesong Yuan and Yang Yan

Electronics 2021, 10(6), 653; https://doi.org/10.3390/electronics10060653 - 11 Mar 2021

Cited by 1 | Viewed by 1794

Abstract

The pill-box window is one of the important components of microwave vacuum electronic devices (VEDs), and research into it is of great significance. As the operating frequency increases, the problems associated with the reduction in the structure size include the reduction of the [...] Read more.

The pill-box window is one of the important components of microwave vacuum electronic devices (VEDs), and research into it is of great significance. As the operating frequency increases, the problems associated with the reduction in the structure size include the reduction of the brazing plane and the reduction in the tolerance of the pill-box window. These problems will cause traditional pill-box windows to be unsuitable in high-frequency bands, especially in terahertz and sub-terahertz regions. The most influential factor is the length of the circular waveguide in the box window. The welding plane of the over-size pill-box window is the annular bottom surface on both sides of the dielectric sheet, which is larger than the circular waveguide, and the operating frequency does not directly affect the area of the brazing surface. Choosing a suitable diameter for the dielectric sheet can effectively increase the tolerance to the length of the pill-box window circular waveguide. Therefore, an over-size pill-box window would be a practicable approach to improve the performance compared to the traditional pillow-box in high-frequency bands. This paper describes, in detail, the theoretical design, simulation optimization and experimental process of this improved pill-box window. An over-size pill-box window suitable for G band VEDs was successfully developed. The experimental result in the 215–225 GHz band is that the maximum transmission loss is −1 dB, and the overall transmission loss is close to −0.5 dB. The overall reflection is less than −11 dB. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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14 pages, 6954 KiB

Open AccessArticle

Investigation on a 220 GHz Quasi-Optical Antenna for Wireless Power Transmission

by Meng Han, Xiaotong Guan, Moshe Einat, Wenjie Fu and Yang Yan

Electronics 2021, 10(5), 634; https://doi.org/10.3390/electronics10050634 - 09 Mar 2021

Cited by 2 | Viewed by 2225

Abstract

This paper investigates a 220 GHz quasi-optical antenna for millimeter-wave wireless power transmission. The quasi-optical antenna consists of an offset dual reflector, and fed by a Gaussian beam that is based on the output characteristics of a high-power millimeter-wave radiation source-gyrotron. The design [...] Read more.

This paper investigates a 220 GHz quasi-optical antenna for millimeter-wave wireless power transmission. The quasi-optical antenna consists of an offset dual reflector, and fed by a Gaussian beam that is based on the output characteristics of a high-power millimeter-wave radiation source-gyrotron. The design parameter is carried on by a numerical code based on geometric optics and vector diffraction theory. To realize long-distance wireless energy transmission, the divergence angle of the output beam must be reduced. Electromagnetic simulation results show that the divergence angle of the output beam of the 5.6 mm Gaussian feed source has been significantly reduced by the designed quasi-optical antenna. The far-field divergence angle of the quasi-optical antenna in the E plane and H plane is 1.0596° and 1.0639°, respectively. The Gaussian scalar purity in the farthest observation field (x = 1000 m) is 99.86%. Thus, the quasi-optical antenna can transmit a Gaussian beam over long-distance and could be used for millimeter-wave wireless power transmission. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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13 pages, 4871 KiB

Open AccessArticle

A Compact Modular 5 GW Pulse PFN-Marx Generator for Driving HPM Source

by Haoran Zhang, Ting Shu, Shifei Liu, Zicheng Zhang, Lili Song and Heng Zhang

Electronics 2021, 10(5), 545; https://doi.org/10.3390/electronics10050545 - 26 Feb 2021

Cited by 21 | Viewed by 4611

Abstract

A compact and modular pulse forming network (PFN)-Marx generator with output parameters of 5 GW, 500 kV, and 30 Hz repetition is designed and constructed to produce intense electron beams for the purpose of high-power microwave (HPM) generation in the paper. The PFN-Marx [...] Read more.

A compact and modular pulse forming network (PFN)-Marx generator with output parameters of 5 GW, 500 kV, and 30 Hz repetition is designed and constructed to produce intense electron beams for the purpose of high-power microwave (HPM) generation in the paper. The PFN-Marx is composed by 22 stages of PFN modules, and each module is formed by three mica capacitors (6 nF/50 kV) connected in parallel. Benefiting from the utilization of mica capacitors with high energy density and a mini-trigger source integrated into the magnetic transformer and the magnetic switch, the compactness of the PFN-Marx system is improved significantly. The structure of the PFN module, the gas switch unit, and the connection between PFN modules and switches are well designed for modular realization. Experimental results show that this generator can deliver electrical pulses with the pulse width of 100 ns and amplitude of 500 kV on a 59-ohm water load at a repetition rate of 30 Hz in burst mode. The PFN-Marx generator is fitted into a cuboid stainless steel case with the length of 80 cm. The ratio of storage energy to volume and the ratio of power to weight of the PFN-Marx generator are calculated to be 6.5 J/L and 90 MW/kg, respectively. Furthermore, utilizing the generator to drive the transit time oscillator (TTO) at a voltage level of 450 kV, a 100 MW microwave pulse with the pulse width of 20 ns is generated. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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11 pages, 2613 KiB

Open AccessArticle

Frequency Tuning Characteristics of a High-Power Sub-THz Gyrotron with Quasi-Optical Cavity

by Xiaotong Guan, Jiayi Zhang, Wenjie Fu, Dun Lu, Tongbin Yang, Yang Yan and Xuesong Yuan

Electronics 2021, 10(5), 526; https://doi.org/10.3390/electronics10050526 - 24 Feb 2021

Cited by 4 | Viewed by 1544

Abstract

Motivated by some emerging high-frequency applications, a high-power frequency-tunable sub-THz quasi-optical gyrotron cavity based on a confocal waveguide is designed in this paper. The frequency tuning characteristics of different approaches, including magnetic field tuning, mirror separation adjustment, and hybrid tuning, have been investigated [...] Read more.

Motivated by some emerging high-frequency applications, a high-power frequency-tunable sub-THz quasi-optical gyrotron cavity based on a confocal waveguide is designed in this paper. The frequency tuning characteristics of different approaches, including magnetic field tuning, mirror separation adjustment, and hybrid tuning, have been investigated by particle-in-cell (PIC) simulation. Results predict that it is possible to realize a smooth continuous frequency tuning band with an extraordinarily broad bandwidth of 41.55 GHz, corresponding to a relative bandwidth of 18.7% to the center frequency of 0.22 THz. The frequency tunability is provided by varying the separation distance between two mirrors and correspondingly adjusting the external magnetic field. During the frequency tuning, the output power remains higher than 20 kW, which corresponds to an interaction efficiency of 10%. Providing great advantages in terms of broad bandwidth, smooth tuning, and high power, this research may be conducive to the development of high-power frequency-tunable THz gyrotron oscillators. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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15 pages, 8573 KiB

Open AccessArticle

Novel Dual Beam Cascaded Schemes for 346 GHz Harmonic-Enhanced TWTs

by Ruifeng Zhang, Qi Wang, Difu Deng, Yao Dong, Fei Xiao, Gil Travish and Huarong Gong

Electronics 2021, 10(2), 195; https://doi.org/10.3390/electronics10020195 - 16 Jan 2021

Cited by 1 | Viewed by 1593

Abstract

The applications of terahertz (THz) devices in communication, imaging, and plasma diagnostic are limited by the lack of high-power, miniature, and low-cost THz sources. To develop high-power THz source, the high-harmonic traveling wave tube (HHTWT) is introduced, which is based on the theory [...] Read more.

The applications of terahertz (THz) devices in communication, imaging, and plasma diagnostic are limited by the lack of high-power, miniature, and low-cost THz sources. To develop high-power THz source, the high-harmonic traveling wave tube (HHTWT) is introduced, which is based on the theory that electron beam modulated by electromagnetic (EM) waves can generate high harmonic signals. The principal analysis and simulation results prove that amplifying high harmonic signal is a promising method to realize high-power THz source. For further improvement of power and bandwidth, two novel dual-beam schemes for high-power 346 GHz TWTs are proposed. The first TWT is comprised of two cascaded slow wave structures (SWSs), among which one SWS can generate a THz signal by importing a millimeter-wave signal and the other one can amplify THz signal of interest. The simulation results show that the output power exceeds 400 mW from 340 GHz to 348 GHz when the input power is 200 mW from 85 GHz to 87 GHz. The peak power of 1100 mW is predicted at 346 GHz. The second TWT is implemented by connecting a pre-amplification section to the input port of the HHTWT. The power of 600 mW is achieved from 338 GHz to 350 GHz. The 3-dB bandwidth is 16.5 GHz. In brief, two novel schemes have advantages in peak power and bandwidth, respectively. These two dual-beam integrated schemes, constituted respectively by two TWTs, also feature rugged structure, reliable performance, and low costs, and can be considered as promising high-power THz sources. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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12 pages, 2788 KiB

Open AccessArticle

Investigation on 220 GHz Taper Cascaded Over-Mode Circular Waveguide TE_0n Mode Converter

by Tongbin Yang, Xiaotong Guan, Wenjie Fu, Dun Lu, Xuesong Yuan and Yang Yan

Electronics 2021, 10(2), 103; https://doi.org/10.3390/electronics10020103 - 06 Jan 2021

Cited by 1 | Viewed by 1615

Abstract

This paper proposes a taper cascaded over-mode circular waveguide TE_0n mode converter for the millimeter and terahertz wave gyrotron. The mode converter of this structure can effectively reduce the difficulty of high frequency mode converter in fabrication. This paper verifies the feasibility [...] Read more.

This paper proposes a taper cascaded over-mode circular waveguide TE_0n mode converter for the millimeter and terahertz wave gyrotron. The mode converter of this structure can effectively reduce the difficulty of high frequency mode converter in fabrication. This paper verifies the feasibility of this new structure from theory, simulation, and experiment. Based on coupled wave theory calculations, three TE₀₂-TE₀₁ mode converters with lengths of 65.43 mm (4 segments), 119.3 mm (6 segments) and 136 mm (8 segments) and a TE₀₃-TE₀₂ mode converter with a length of 92 mm (8 segments) are optimized. The conversion efficiency in the frequency band 215–225 GHz is 91.8–94%, 93–95%, 95–98.78% and 95–98.44%. Because the length of the mode converter is clearly limited, this paper selects the TE₀₂-TE₀₁ mode converter with a length of 65.43 mm (4 segments) and the TE₀₃-TE₀₂ mode converter with 92 mm (8 segments) for simulation and experimental verification. In the simulation software Computer simulation technology (CST), the TE₀₂-TE₀₁ and TE₀₃-TE₀₂ mode converters and their composed TE₀₃-TE₀₁ mode converters are selected for modeling and analyzing. The simulation results and theoretical calculation results of the three mode converters only have different degrees of frequency deviation, and the frequency deviation of the 4-stage TE₀₂-TE₀₁ mode converter can be ignored; the frequency deviations of TE₀₃-TE₀₂ mode converter and TE₀₃-TE₀₁ mode converter are 2 GHz and 3 GHz, respectively. The experimental system is a field scanning system based on a vector network analyzer (VNA), which scans the input and output of the mode converter respectively. The experimental result is that when the input mode purity is 92% in TE₀₁ mode, the output mode TE₀₃ mode has a mode purity of 82%, and it has lower transmission loss. In this paper, the results from theory, simulation and experiment are in good agreement. This type of mode converter is easy to prepare, which makes it an effective alternative for high frequency curvilinear waveguide mode converter. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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10 pages, 4415 KiB

Open AccessArticle

Investigation on Symmetric and Asymmetric Broadband Low-Loss W-Band Pillbox Windows

by Tongbin Yang, Xiaotong Guan, Wenjie Fu, Dun Lu, Chaoyang Zhang, Jie Xie, Xuesong Yuan and Yang Yan

Electronics 2020, 9(12), 2060; https://doi.org/10.3390/electronics9122060 - 03 Dec 2020

Cited by 1 | Viewed by 1536

Abstract

In order to develop wide-band low-loss windows for W-band vacuum electronic devices and easily fabricate them, symmetric and asymmetric pillbox windows are investigated and reported in this paper. A symmetric pillbox window and an asymmetric pillow-box window were designed, simulation optimized, fabricated, and [...] Read more.

In order to develop wide-band low-loss windows for W-band vacuum electronic devices and easily fabricate them, symmetric and asymmetric pillbox windows are investigated and reported in this paper. A symmetric pillbox window and an asymmetric pillow-box window were designed, simulation optimized, fabricated, and tested. The initial parameters for the two pillbox windows were designed by equivalent circuit theory. Computer simulation technology (CST) three-dimensional (3D) electromagnetic simulation software was used to verify and optimize the design. Because of the uncontrollability of welding during the experiment, this article provides two solutions. One is to measure and reprocess the symmetrical pillbox window with the dielectric sheet welded to reduce the influence of welding on the measurement results; the other is an asymmetrical box window which is designed to avoid the error caused by the welding of the box window. The best experimental results for the symmetric pillbox window were |S₂₁| close to 1 dB and reflection parameter |S₁₁| close to 10 dB in the frequency range of 77–110 GHz. The experimental results for the asymmetric pillbox window were |S₂₁| < 1 dB nearly in the frequency range of 76–109.5 GHz. The experimental results show that both solutions efficiently complete the design of broadband pillbox windows and would potentially be operated in the gigahertz millimeter-wave region. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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11 pages, 3780 KiB

Open AccessArticle

Ultra-High Velocity Ratio in Magnetron Injection Guns for Low-Voltage Compact Gyrotrons

by Dun Lu, Wenjie Fu, Xiaotong Guan, Tongbin Yang, Chaoyang Zhang, Chi Chen, Meng Han and Yang Yan

Electronics 2020, 9(10), 1587; https://doi.org/10.3390/electronics9101587 - 28 Sep 2020

Cited by 2 | Viewed by 2122

Abstract

Low-voltage compact gyrotron is under development at the University of Electronic Science and Technology of China (UESTC) for industrial applications. Due to the low operating voltage, the relativistic factor is weak, and interaction efficiency could not be high. Therefore, a magnetron-injection gun (MIG) [...] Read more.

Low-voltage compact gyrotron is under development at the University of Electronic Science and Technology of China (UESTC) for industrial applications. Due to the low operating voltage, the relativistic factor is weak, and interaction efficiency could not be high. Therefore, a magnetron-injection gun (MIG) with an extremely high-velocity ratio α (around 2.5) is selected to improve the interaction efficiency. As beam voltage drops, space charge effects become more and more obvious, thus a more detailed analysis of velocity-ratio α is significant to perform low-voltage gyrotrons, including beam voltage, beam current, modulating voltage, depression voltage, cathode magnetic field, and magnetic depression ratio. Theoretical analysis and simulation optimization are adopted to demonstrate the feasibility of an ultra-high velocity ratio, which considers the space charge effects. Based on theoretical analysis, an electron gun with a transverse to longitudinal velocity ratio 2.55 and velocity spread 9.3% is designed through simulation optimization. The working voltage and current are 10 kV and 0.46 A with cathode emission density 1 A/cm² for a 75 GHz hundreds of watts’ output power gyrotron. Full article

(This article belongs to the Special Issue Design, Technologies and Applications of High Power Vacuum Electronic Devices from Microwave to THz Band)

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