Jinjun Feng
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View article: A G-Band Pulsed Wave-Traveling Wave Tube for THz Radar
A G-Band Pulsed Wave-Traveling Wave Tube for THz Radar Open
The growing interest in high-power amplifiers for the terahertz (THz) radar system leads to significant performance improvements of THz wave traveling-wave tubes (TWT). This article presents a detailed development of a G-band pulsed wave T…
View article: Very high frequency (263 GHz) pulse EPR spectroscopy of high spin transition metal centers
Very high frequency (263 GHz) pulse EPR spectroscopy of high spin transition metal centers Open
Pulse Electron Paramagnetic Resonance (EPR) spectroscopy provides powerful tools for examining species with unpaired electrons, such as organic radicals and metal ions, in a wide variety of interesting systems. However, the lack of high po…
View article: Surpassing kilometer-scale terahertz wireless communication beyond 300 GHz enabled by hybrid photonic–electronic synergy
Surpassing kilometer-scale terahertz wireless communication beyond 300 GHz enabled by hybrid photonic–electronic synergy Open
Terahertz (THz) bands are critical for next-generation wireless fronthaul/backhaul applications. However, they face a fundamental coverage range limitation due to low emission power, severe path loss, and poor receiving sensitivity, especi…
View article: Correction: The impact of internet pornography addiction on brain function: a functional near-infrared spectroscopy study
Correction: The impact of internet pornography addiction on brain function: a functional near-infrared spectroscopy study Open
[This corrects the article DOI: 10.3389/fnhum.2025.1477914.].
View article: Pump-induced stimulated superradiant Smith-Purcell radiation with ultra-narrow linewidth
Pump-induced stimulated superradiant Smith-Purcell radiation with ultra-narrow linewidth Open
Lasers with the gain medium of gas, liquid, semiconductor, and solid could generate coherent light with rather narrow spectral linewidth, which play an important role in the fields of communication, measurement, sensing, and so on. Althoug…
View article: The impact of internet pornography addiction on brain function: a functional near-infrared spectroscopy study
The impact of internet pornography addiction on brain function: a functional near-infrared spectroscopy study Open
Introduction There is extensive awareness of internet pornography addiction. It not only affects the mental health of adolescents but also promotes criminal activity. However, the impact of internet pornography addiction on functional in t…
View article: Calculation of thermal initial velocity spread based on the non-parallel electrode plate model
Calculation of thermal initial velocity spread based on the non-parallel electrode plate model Open
Microwave electron vacuum devices convert the DC electrical energy carried by electrons into microwave energy through the motion of electrons in a vacuum. This principle determines that the electron beam and the high-frequency field are th…
View article: Research on the Withstand Voltage Properties of Cr/Mn-Doped Al2O3 Ceramics in Vacuum
Research on the Withstand Voltage Properties of Cr/Mn-Doped Al2O3 Ceramics in Vacuum Open
Al2O3 ceramics are widely used in vacuum electronic devices. However, surface flashover in a vacuum during the application of high voltage significantly influences their reliability and restricts the development of vacuum electronic device…
View article: Optimized Design and Experimental Study of an Axis-Encircling Beam with Gently Varying Cusp Magnetic Field
Optimized Design and Experimental Study of an Axis-Encircling Beam with Gently Varying Cusp Magnetic Field Open
Mode competition is a significant barrier to advancing gyrotrons towards high frequency, high power, and high efficiency. An axis-encircling beam enables gyrotrons to achieve high interaction efficiency while maintaining stable operation a…
View article: Cathode Thermal Experiment Improves Performance of Magnetron Injection Gun for 170 GHz Gyrotron
Cathode Thermal Experiment Improves Performance of Magnetron Injection Gun for 170 GHz Gyrotron Open
This paper details the design and fabrication of a triode–anode magnetron injection gun (MIG) for a 170 GHz gyrotron for use in magnetic confinement thermonuclear fusion. To solve the mismatch problem of electric and magnetic fields in the…
View article: Diversity and phylogeny of yeasts in various habitats of the Arctic and Antarctic regions, with descriptions of one new family, five new genera and eighteen new species
Diversity and phylogeny of yeasts in various habitats of the Arctic and Antarctic regions, with descriptions of one new family, five new genera and eighteen new species Open
The Arctic and Antarctic regions are characterized by low temperatures, high solar irradiation, and successive freezing and thawing cycles. To date, 57 yeast species belonging to 24 genera have been identified as novel taxa initially isola…
View article: Microfabrication Technologies for Interaction Circuits of THz Vacuum Electronic Devices
Microfabrication Technologies for Interaction Circuits of THz Vacuum Electronic Devices Open
Advances in manufacturing technology are allowing for the realization of interaction circuit with microstructures. The capability to produce small circuit structures is allowing new opportunities for vacuum electronic devices producing ter…
View article: Study on pseudospark switch with high repetition frequency with double-pulse triggering
Study on pseudospark switch with high repetition frequency with double-pulse triggering Open
The pseudospark switch works in the left branch of Paschen curve with low gas pressure, which has the advantage of short electrode breakdown time (<10ns), large pulse current (>100kA), and long lifetime, etc. High pulse repetition frequenc…
View article: Research on a Ka‐band large‐orbit gyro‐TWT with periodic dielectric‐loaded structure
Research on a Ka‐band large‐orbit gyro‐TWT with periodic dielectric‐loaded structure Open
This paper presents a design of a gyro‐TWT operating in the large‐orbit electron beam mode, with the aim of reducing the working magnetic field while ensuring operational efficiency. The periodic dielectric‐loaded structure, which has been…
View article: Research on a Ka-band large-orbit gyro-TWT with periodic dielectric-loaded structure
Research on a Ka-band large-orbit gyro-TWT with periodic dielectric-loaded structure Open
This paper presents a design of a gyro-TWT operating in the large-orbit electron beam mode, with the aim of reducing the working magnetic field while ensuring operational efficiency. The periodic dielectric-loaded structure is adopted as t…
View article: Investigation of Spindt Cold Cathode Electron Guns for Terahertz Traveling Wave Tubes
Investigation of Spindt Cold Cathode Electron Guns for Terahertz Traveling Wave Tubes Open
In this work, a Spindt cold cathode electron gun with a PPM (periodic permanent magnet) focusing system for a terahertz TWT (traveling wave tube) was designed and simulated based on the Pierce electron gun structure. More specifically, a n…
View article: Demonstration of a 263-GHz Traveling Wave Tube for Electron Paramagnetic Resonance Spectroscopy
Demonstration of a 263-GHz Traveling Wave Tube for Electron Paramagnetic Resonance Spectroscopy Open
In this letter, a 263 GHz traveling wave tube for electron paramagnetic resonance spectroscopy is designed, fabricated and tested. A periodic permanent magnet focused pencil beam electron optical system is adopted. A folded waveguide slow-…
View article: Performance evaluation and experimental study of a 0.34 THz folded waveguide sheet beam BWO
Performance evaluation and experimental study of a 0.34 THz folded waveguide sheet beam BWO Open
Terahertz (THz) backward wave oscillators (BWOs) hold immense potential for a wide range of military and industrial applications. This study presents a comparative analysis of 0.34 THz sheet beam (SB) and circular beam (CB) folded waveguid…
View article: A Method for non-destructive testing of resonant frequency in the W-band second harmonic gyrotron complex cavity
A Method for non-destructive testing of resonant frequency in the W-band second harmonic gyrotron complex cavity Open
In this study, the HFSS is utilized to obtain the field distribution and resonant frequency of the gyrotron complex cavity. The resonant frequency of the complex cavity is experimentally tested with mode converters, and the correctness of …
View article: Design of an ultrashort H‐plane coupler without transition structure for sheet beam traveling‐wave tube amplifier at W‐band
Design of an ultrashort H‐plane coupler without transition structure for sheet beam traveling‐wave tube amplifier at W‐band Open
An ultrashort H‐plane sheet beam traveling‐wave tube (SB‐TWT) coupler without transition structure is proposed. The coupler adopts a new idea of directly coupling the microwave from H‐plane of the slow‐wave circuit (SWC) and optimizes the …
View article: A 237 GHz Traveling Wave Tube for Cloud Radar
A 237 GHz Traveling Wave Tube for Cloud Radar Open
In this article, the first 237 GHz traveling wave tube (TWT) is presented as a high-power amplifier for the terahertz (THz) cloud radar. As is common with previous G-band traveling wave tubes developed at Beijing Vacuum Electronics Researc…
View article: Frontiers in the Application of RF Vacuum Electronics
Frontiers in the Application of RF Vacuum Electronics Open
The application of radio frequency (RF) vacuum electronics for the betterment of the human condition began soon after the invention of the first vacuum tubes in the 1920s and has not stopped since. Today, microwave vacuum devices are power…
View article: Review of Nanoscale Vacuum Devices
Review of Nanoscale Vacuum Devices Open
The newly developed nanoscale vacuum devices have basic functions similar to traditional vacuum tubes, but can be manufactured by existing silicon-based process lines to achieve small size, light weight, and high integration, which makes t…
View article: Vertical Nanoscale Vacuum Channel Triodes Based on the Material System of Vacuum Electronics
Vertical Nanoscale Vacuum Channel Triodes Based on the Material System of Vacuum Electronics Open
Nanoscale vacuum channel triodes realize the vacuum-like transmission of electrons in the atmosphere because the transmission distance is less than the mean free path of electrons in air. This new hybrid device is the deep integration of v…
View article: High-Frequency Vacuum Electron Devices
High-Frequency Vacuum Electron Devices Open
Vacuum electron devices at frequencies of millimeter waves and terahertz play highly important roles in the modern high-data rate and broadband communication systems, high-resolution detection and imaging, medical diagnostics, magnetically…
View article: A G-Band Broadband Continuous Wave Traveling Wave Tube for Wireless Communications
A G-Band Broadband Continuous Wave Traveling Wave Tube for Wireless Communications Open
Development of a G-band broadband continuous wave (CW) traveling wave tube (TWT) for wireless communications is described in this paper. This device provides the saturation output power over 8 W and the saturation gain over 30.5 dB with a …
View article: Terahertz Rectangular Waveguides by UV-LIGA with Megasonic Agitation
Terahertz Rectangular Waveguides by UV-LIGA with Megasonic Agitation Open
This paper researches the fabrication of a WR2.8 terahertz rectangular waveguide operating at the frequency ranging from 260 GHz to 400 GHz via UV-LIGA technology (UV-lithography, electroplating, and molding). In the process, megasonic agi…
View article: Design of optically pumped cesium beam tube with hexapole magnetic system for longer lifetime and better SNR
Design of optically pumped cesium beam tube with hexapole magnetic system for longer lifetime and better SNR Open
In order to get a better tradeoff between the long lifetime and high performances of cesium beam atomic clocks, we proposed a design scheme of compact optically pumped cesium beam tube (OPCBT) based on hexapole magnetic focusing (HMF) syst…