A5103138675- Gyrotron and Vacuum Electronics Research
- Particle accelerators and beam dynamics
- Pulsed Power Technology Applications
- Microwave Engineering and Waveguides
- Particle Accelerators and Free-Electron Lasers
- Plasma Diagnostics and Applications
- Electronic Packaging and Soldering Technologies
- Plasma Applications and Diagnostics
- Terahertz technology and applications
- Nanomaterials and Printing Technologies
- Vacuum and Plasma Arcs
- Magnetic confinement fusion research
- Antenna Design and Analysis
- Electrodeposition and Electroless Coatings
- Electromagnetic Compatibility and Noise Suppression
- Silicon Carbide Semiconductor Technologies
- Advanced Antenna and Metasurface Technologies
- Copper Interconnects and Reliability
- Superconducting and THz Device Technology
Kunming University of Science and Technology
2024-2025
Northwest Institute of Nuclear Technology
2010-2024
Purdue University West Lafayette
2022
A new technique for time-stamping bunches of electrons with terahertz pulses allows the electron arrival time to be recorded 1.5-fs accuracy, paving way greatly improved resolution in apparatuses that probe ultrafast, atomic-scale processes.
The mechanisms of nanosecond microwave-driven discharges near a dielectric/vacuum interface were studied by measuring the time- and space-dependent optical emissions pulse waveforms. experimental observations indicate multipactor plasma developing in thin layer several millimeters above interface. emission brightness increases significantly after main pulse, but region widens little. are analysis simulation, revealing intense ionization concentrated desorbed high-pressure layer, leading to...
The effect of periodic rectangular grooves on vacuum multipactor has been theoretically and experimentally investigated. Dynamic calculation is applied to research the electron trajectory impact energy under groove surface. Two-dimensional electromagnetic particle-in-cell simulation used analyze compare scenario, statistic energy, secondary emission yield flat surface with that corrugated It found by computational simulative analysis grooved can explicitly suppress in developmental stage...
The anti-oxidation of silver-coated copper powders is improved by forming a thick silver shell on the surface core through cobalt modification.
Abstract The field distribution and the restraint effect of multipactor plasma discharge on periodic triangular surface have been theoretically experimentally analyzed. It has found by computational simulative analysis that profile can quickly restrain or weaken in low pressure within several microwave periods. Considering enhancement, increasing slope angle, advancing electric field, lowering frequency enhance suppression. X-band giga-watt high power experiment with 20 ns short pulse was...
Design and optimization of high-power microwave (HPM) feed horn by combining the aperture fleld with radiation patterns are presented in paper. The optimized C band satisfles relatively uniform fleld, power capacity higher than 3GW, symmetric patterns, low sidelobes, compact length. Cold tests HPM experiments were conducted to investigate horn. theoretical consistent cold test experimental results. has been demonstrated be 3GW.
A low magnetic field relativistic backward wave oscillator with single mode structure is presented. Particle-in-cell simulation results show that 1.25 GW output power 37% efficiency generated under 0.88 T. The purity of the signal high because higher modes are cut off by structure. According to analytical results, influence bombardment electrons on surface slow structures minor. modulation cavity adopted enhance beam-wave interaction and realize mechanical frequency tunability. capacity...
We propose and demonstrate a novel method to produce few-femtosecond electron beam with relatively low timing jitter. In this relativistic is compressed from about 150 fs (rms) 7 (rms, upper limit) the wakefield at THz frequency produced by leading drive in dielectric tube. By imprinting energy chirp passive way, we through laser-driven streaking technique that no additional jitter respect an external laser introduced bunch compression process, prominent advantage over conventional using...
A high efficiency relativistic backward wave oscillator working at a low guiding magnetic field is designed and simulated. trapezoidal resonant reflector used to reduce the modulation in avoid overmodulation of electron beam which will lead large momentum spread then conversion efficiency. The envelope inner radius slow structure (SWS) increases stepwise keep conformal trajectory alleviate bombardment on surface SWS. length period SWS reduced gradually make better match between phase...
An improved global model is proposed to analyze high power microwave dielectric window breakdown at low pressure. The effect of ionization on the average momentum and energy electrons taken into account a Maxwellian electron distribution function adopted. plasma flow density loss dielectric, partially secondary returning compensate loss, have been analytically considered. Space charge potential drop generalized Bohm criterion are deduced analytically. After considering as well compensation,...
A method for generating high power beating radio-frequency wave with conversion efficiency is proposed. Based on Cherenkov radiation, two longitudinal resonant modes are excited simultaneously and interacted intense electron beam synchronously. An experiment was carried out beat-waves an average of about 2.3 GW, frequencies 9.29 GHz 10.31 GHz, 40% were obtained. Through controlling the energy, amplitude proportions altered, different beat-wave patterns formed.
Spherical copper powders and cobalt-modified were electroless plated with silver, respectively, to obtain two kinds of silver-plated powders. The composite analysed by X-ray diffraction, photoelectron spectroscopy, scanning electron microscopy thermogravimetric-differential calorimetry. Effects cobalt modification on surface morphology, silver reduction rate, particle size anti-oxidisation resistance studied. results indicate that morphology silver-coated prepared was affected cobalt, but...
Surface breakdown of dielectric window seriously limits the transmission high power microwave (HPM), which blocks development technology. Under X-band HPM with level 1 GW at 9.4 GHz, experiments were conducted several materials including polytetrafluoroethylene (PTFE), low-density polyethylene (LDPE), high-density (HDPE) and polymethyl methacrylate (PMMA) in vacuum. The influence different surface treatments for PTFE notching polishing on its characteristics is also studied. After breakdown,...
This article presents the results of numerical and experimental study a Ka-band Cherenkov oscillator with average diameter slow wave structure (SWS) D = 2.4λ, where λ is wavelength. The operating point on TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> set close to π-point enhance electric field in SWS. Meanwhile, by optimizing structural parameters, influence xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> mixed output mode...
A prototype of an integrated coaxial cusped periodic permanent magnet (CPPM) system is put forward and optimized. The guiding magnetic field strength period the CPPM are 0.32 T 30 mm, respectively, whole focusing 240 mm long, with a maximum diameter 170 total weight under kg. Using this system, oversized Ku-band relativistic Čerenkov generator proposed investigated. Particle-in-cell simulation shows that microwave output power 830 MW at 15.29 GHz achieved, yielding conversion efficiency 37%....
A Ku band coaxial high power microwave generator with a low magnetic field was investigated without mode competition in this paper. Mode is avoided physically by adopting two-cavity extractor instead of three-cavity to eliminate the resonance between modulation slow wave structure and at any unexpected frequency except working frequency. Moreover, efficiency device increases due separation process energy extraction electron collection inner conductor collecting structure. Particle simulation...
The emission uniformity of an annular knife-edged cathode in a coaxial diode with focusing electrode and operating low macro electric field has been investigated. It was found that the deteriorated as width increased from 0.5 mm to 2.0 mm. To improve uniformity, grooved graphite prepared by laser micro-etching treatment. Experimental results demonstrated threshold for may be reduced thus delay explosive can decreased. Visual inspection photographs plasmas under different guiding magnetic...
This paper investigates the dependence of properties spatial harmonics on overmoded ratio corrugated waveguide operating in TM01 at 30 GHz with consideration effects ripple shape. It is found that as grows, electric fields concentrate towards surface, which weakens enhancement power handling capacity caused by augmentation ratio. As between field amplitudes -1st harmonic and fundamental increases monotonically. Therefore, total composed become beating-wave single frequency, whose vary along...
A high power capacity relativistic backward wave oscillator with an electron collection cavity (ECC) placed at the downstream of slow structure (SWS) is presented. The breakdown threshold increased, and density seed suppressed by preventing secondary electron, plasma, powder generated from bombardment spent beam on surface collector drifting to extractor beam-wave interaction region. maximum longitudinal electric field in device reduced through extension span between weakening Cerenkov...
High-power microwave (HPM) antenna, one of the key subsystems in HPM system, is used for radiation. Its performance partly determined by impulse responses reflector materials under HPM. Therefore, it essential to investigate response characteristics Instead traditional waveguide cavity, this study was based on double elliptical system with an open boundary. By using measured, and multiple types various environments different electric field strengths pulse widths tested. In terms breakdown,...
For the high power microwave (HPM) generator, damage on an RF structure surface is harmful for a long time operation. In this paper, we investigate traces slow-wave (SWS) of relativistic backward-wave oscillator (RBWO) with low guiding magnetic field. By theoretical and experimental analysis, find that SWS are mainly caused by bombardment beam electrons pulled back. Moreover, it suggested not breakdown, secondary electrons, particles from collector plasma. Importantly, to decrease damages...
In the case of characterizing waveguide mode converter, widely applied back-to-back method can only extract two converters' joint S-parameters, accuracy far-field radiation pattern is limited. This paper experimentally demonstrates a for accurately single circular TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> -TE xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> which consists extracting asymmetric two-port and TE generator test...
Applying an external magnetic field perpendicular to the electric across gap causes electron emitted from cathode fail reach anode when B exceeds Hull cutoff H [1] . For sufficiently low injected current density J , this results in a cycloidal orbit; exceeding critical c may cause turbulent steady state, called near-Brillouin (nB) state [2] which also arise due resistance or adding small AC voltage applied DC [3] However, 1-D theory and particle-in-cell (PIC) simulations only considered...