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Design improvements and fabrication of a 10 MW, 1.3 GHz Annular Beam Klystron are described. The principal improvement is the electron gun. Utilization of a Controlled Porosity Reservoir (CPR) cathode allows the use of a zero-compression gun, resulting in improved beam quality and reductions in the gun and solenoid diameters.
A 220 GHz power amplifier has been demonstrated as part of the DARPA HiFIVE program. This amplifier is based on a folded waveguide circuit, and operates at 19 kV and 250 mA. Short pulse tests resulted in 56 W at 214 GHz and a 5.0 GHz bandwidth.
Fabrication of carbon nanotube cold cathode requires an efficient and low cost process. In the paper, carbon nanotube is direct synthesized on stainless steel which acts as cathode substrate and catalyst for growing carbon nanotube. The best type of stainless steel is chosen and investigated its effect on the synthesis quality of carbon nanotube. The field emission character of carbon nanotube on...
It is found that the Langmuir-Blodgett (LB) solutions for the space charge limited current density, for both cylindrical and spherical diodes, may be approximated by Japp =(4/9)ε0(2e/m)1/2Ec3/2/D1/2 over a wide range of parameters, where Ec is the surface electric field on the cathode of the vacuum diode and D is the anode-cathode spacing. This dependence is valid whether Ra/Rc is greater than or...
In this paper, we have presented the simulation results on sheet beam electron gun and sheet beam transport in a uniform magnetic field. It is shown that the sheet beam with size 4.6 mm×0.4 mm, generated by the electron gun with 20 kV, 560 mA, can stably pass through the beam tunnel with transverse size 6 mm×1 mm and the length 120 mm in a uniform magnetic field.
We put forward a new type impregnated dispenser cathode, which impregnates the active salt of BaO/SrO/Sc2O3. At 1100UB, the pulse current density of the cathode is up to 86.2A/cm2, 2.7 times of the value of a traditional M-type cathode. It is proposed that, the emission of pores and pore edges caused by Sc2O3 and SrO is the main reason that the new cathode has excellent emission performance.
This paper presents the simulation study of a C band klystron with a disc-load waveguide traveling wave output structure. The electron gun with a perveance of 1.5μp is designed. A 3-cell disc-loaded waveguide output structure working at π/2 mode is adopted in the circuit design. The beam-wave interaction system with disc-loaded waveguide output structure is simulated by PIC code. More than 50MW output...
Classical Child-Langmuir law(CL law) analytically demonstrates maximum steady current density transported. Á. Valfells et al. in 2002 presented its analytic modification under short pulse case. However, both above have not touched time-dependence problem. In this paper, an iterative calculation method to consider time-dependent short-pulse of electron flow is developed, confirmed by particle-in-cell(PIC)...
Density functional theory was used to calculate the surface electron emission barriers for the stable (011) and (111) surfaces of bixbyite Sc2O3 in the presence of adsorbed Ba and Ba-O. A low surface barrier of 1.21 eV for a defected BaO monolayer on Sc2O3 (011) was found to be thermodynamically stable. This result provides a straightforward explanation of low effective work function measurements...
A good quality graphene is transferred onto honeycomb-like CNTs arrays with inner supporting CNTs. The efficient field emission is demonstrated due to a high aspect ratio protrusions and graphene crack edges. A high efficient current density about 1.2 mA/cm2 at threshold electric field of 7.8 V/μm with a turn-on electric field of 1.8 V/μm at the current density of 10 μA/cm2 is observed due to high...
To find the changes of surface compositions during life time of the Scandia-doped impregnated dispenser cathodes, two cathodes have been tested at an activation temperature of 1150°CB-Mo and an operation temperature of 1000°CB-Mo, respectively, in an AES system up to more than 7,000 hours. Surface compositions were monitored in-situ at intervals. The tested results have been reported and discussed...
The Recirculating Planar Magnetron (RPM) is a crossed-field device which presents numerous potential advantages in generating High Power Microwaves (HPM). A 12-cavity, conventional-polarity, 1-GHz RPM model has been experimentally designed and tested at a −300 kV, 0.3–0.5 microsecond pulselengths and a 0.2 T axial magnetic field. The experimental results and future concepts are under investigation.
In filament-free magnetrons which are activated by electron emission from field-radiating cathodes its necessary level is provided by adsorption of active metal barium coming from the main palladium-barium cathode. The developed pressed palladiumbarium cathode allows to change barium evaporation speed due to change of its porosity and hence barium Knudsen flow. It will lead to emission level control...
Impregnated thermionic cathodes production was the main objective of this work. The W-30wt.%Cu composite was sintered by induction heating (1200°C). The porous matrix was obtained after decopperization (1600°C). High purity Ba-Ca aluminate was impregnated (1630°C). The amount of aluminate impregnated was 18.32wt.%. Microstructure, porosity, and particle sizes distribution were determined.
The reasons of limitations in field emitter implementation in powerful RF tubes are investigated, overcoming ways are discussed. The results of electron beam optic system (EOS) design with planar type matrices of field emission cathodes and intense beams with power above 100 kW in CW mode are presented.
A sealed off magnetron injection gun (MIG) collector module for 42 GHz 200 kW gyrotron has been developed. The paper reports the high voltage and beam-emission test result. In addition, the current-voltage characteristics at different heater wattage are also discussed from recent tests.
Electric fields at metal-dielectric contact were calculated analytically and numerically. The obtained field exhibited enhancements strong enough to cause breakdown at a triple junction and more apparently at a quadruple junction. Such field enhancements may lead to a noble type of cold cathode.
A novel model of the compact high power 264 GHz CW Extended Interaction Oscillator has been developed by CPI Canada. By combination of mechanical tuning and electronic switching between two operating modes, this EIO provides over 1 W of power in the range of 258 to 270 GHz. Liquid cooling is used to stabilize RF circuit temperature and prevent frequency detuning. Further development is ongoing to...
In this paper, the design and optimization of a V-band helix TWT is carried out and prototype tubes have been assembled. The test results show that the output power of the TWT is over 15W with the overall efficiency of over 14.5% and a gain of over 43dB. The beam transmission experiment shows that a transmission ratio is over 97%.
Electron emission characteristics of a triode surface-conduction field emission display were simulated with finite element analysis method and MATLAB. The parameters of the display structure were optimized based on the simulation results. Field emission from the carbon nanotubes and ZnO nanotetrapod compound cathodes were also simulated and studied.
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