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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...
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.
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)...
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...
Different concepts for corkscrew modulated klystrons are presented. Special attention is paid to the generation of multiple twisted beams to reduce current density in high power applications. Furthermore, the possibility of simple frequency multiplication in the output and idler cavities is addressed.
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.
Recently, a set of instrument named Electron Beam Measuring and Analyzing System (EBMAS) has being built in Institute of Electronics, Chinese Academy of Sciences (IECAS), which can be used to measure the dynamic parameters for the high power electron beam during its formation and transport for microwave vacuum electron devices. In this paper, the EBMAS with its measurement of cross section, current...
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.
We report on the incorporation of a model of field emitters based on a Point Charge Model (PCM) that allows for rapid and analytical representations of tip current, variation, and emission statistics and its implementation and usage in the MICHELLE Particle-In-Cell (PIC) code to model the impact of emission variation on current characteristics and emittance. Rather than cold field emission characterized...
Analysis of a quadrupole focusing lattice for high-frequency TWT's is presented. Single particle tracking is performed to determine the phase advance, with the eventual goal of determining the advantageous frequency regime for devices using this focusing method. This work is motivated by recent work which demonstrated an advantageous case for strong focusing employing a Halbach quadrupole lattice.
Cadmium sulphide-polyaniline (CdS-PANI) nanotube composite was synthesized in two steps. Simple chemical oxidative polymerization has been used to synthesize PANI nanotubes in the first step, which are used further to form nanocomposite with CdS nanoparticles in the second step. The structural, optical and chemical properties of the CdS-PANI nanotube composite are revealed using XRD, UV-visible TEM,...
In recent years an exciting progress has been made in developing scandate cathodes that have excellent emission properties at a lower operating temperature comparing to the traditional sintered tungsten dispenser cathodes, and consequently a significantly longer life. The initial results look very promising for the development of millimeter wave and THz sources. In order to compare performance of...
Efforts are continuing to improve the quality of controlled porosity reservoir cathodes and measure performance. CPR cathodes are being incorporated into several new configurations, including a magnetron injection gun, 15-beam klystron, and a Pierce gun for a 50 MW X-Band klystron. Improved computational tools assist users in CPR cathode design.
Method of obtaining sintered and pressed composed materials based on BaxSr1−xHfO3, where x = 0.25, 0.50, 0.75, with 16, 20, 24, 60 % W (by mass), and experimental results of thermionic properties investigations of these materials are represented. The composition of 80% Ba0.75Sr0.25HfO3 — 20% W (by mass) is characterized by the thermionic current density of 1014 A/cm2 at T = 1620 K.
It has proved that the superior emission capability of a new type impregnated dispenser cathode through impregnates the BaO/SrO/Sc2O3 active substances and covers a mixture W+BaO/SrO/Sc2O3 coating by the pulse laser deposition. However, the thermionic emission of this impregnated dispenser cathode at low temperature is not clear. Our results illustrate that the Current-voltage characteristics of this...
Plasma assisted microwave devices are unique source for microwave radiation. This paper presents the status for development of X-band Plasma Assisted Slow Wave Oscillator (PASOTRON) of peak power 0.5MW.
Sc2O3 doped W nano-powder is believed to play a dominant role for improving emission capabilities of the high current density thermionic cathodes. In this study a novel nano-particle synthesis approach was adopted in order to precisely control the particle parameters. The particle characteristics and sintering behavior has been analyzed using SEM, TEM, EDS, XRD and XPS. Uniform grain size with average...
A 15-beam electron gun was designed, fabricated, and installed on a 100 KW, X-Band klystron. The gun uses controlled porosity reservoir (CPR) cathodes operating at 30 A/cm2 to provide the high quality electron beams for the RF circuit. Because the CPR cathodes can provide such a high current density with a long lifetime, the beam can be generated without compression. This greatly simplifies the gun...
In this work we present a carbon nanotubes electron source assembled with a low cost technique. We used a carbon nanotube cathode that reached the remarkable current density of 0,6 A/cm2. The cathode has been assembled with an external grid in a compact electron source that achieved a maximum output current density of 45 mA/cm2. This represents one the first examples of a CNTs electron source realized...
Precision fabrication and RF testing of a 220 GHz GHz sheet beam TWTA based on the double vane half-period staggered slow wave structure design[1]is reported. Nano-CNC Milling technology[2] was employed to precision fabricate the entire TWTA circuit in bulk copper, incorporating input and output couplers, sever ports, and the slow wave structure with matching. To accommodate an overhead input/output...
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