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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...
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)...
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...
We report on a new cathode which is based on die-pressed matrices made from scandia-doped tungsten powder. Transition temperatures from space charge to temperature limited emission are as low as 840° Cb(W) for emission of 5 Amps/cm2. Transitions are sharper than previously published scandate cathodes and compare favorably with M and ternary alloy cathodes. We present emission curves on several cathodes,...
This paper summarizes a calculation of the mean and standard deviation of the small signal gain and phase of a TWT in the presence of small random, axially varying perturbations in the circuit phase velocity using numerical and analytic approaches. The analytical results compare favorably with results from numerical computations in the absence of space charge effects. The effects of small pitch errors...
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