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The paper reviews the state-of-the-art in studying the physical processes that occur in the cathode spots of vacuum arcs. The main relevant experimental data are interpreted in the context of the ecton model of the cathode spot of a vacuum arc. Central to the ecton model is explosive electron emission, the phenomenon discovered by the author and his collaborators in the mid 60th of the last century...
The mode analysis in a klystron-like relativistic backward wave oscillator (RBWO) with a transverse dimension to free-space wavelength about four is presented. The particle in cell simulations with a 2.5-D full electromagnetic code reveal that microwaves with power of 1.75 GW, frequency of 13.7 GHz are generated with efficiency of 42% when diode voltage is 380 kV, beam current 11 kA, and magnetic...
In this work, a self-consistent general thermal field (GTF) emission model is formulated and the space charge effect on the original GTF equation developed by Jensen at NRL is studied analytically. We have also implemented the GTF algorithm in VORPAL, a conformal finite-difference timedomain (CFDTD) particle-in-cell (PIC) code. This analytic model could serve as a benchmark standard for the GTF CFDTD...
Explosive emission cathodes are generally used to produce high-power electron beams1, 2. Therefore, considerable study is being given to the expanding cathode plasma, its characteristics, and the velocity of motion of the plasma front at the initial stage of explosive emission, when we deal with essentially nonideal high-density plasma. One of the most important problems in constructing a model of...
The initiation of the explosive electron emission pulses - ectons being responsible for the ignition and burning of a vacuum discharge, in particular, - unipolar arcs1. The latter being a common feature of intense plasma-surface interactions in fusion devices. A fusion devices first wall with a strongly non-uniform surface, as well as an intense power load onto the surface in the edge localized modes...
The plasma-surface interaction in the presence of strong thermionic or secondary electron emission has been studied theoretically and experimentally both as a basic phenomenon and in relation to numerous plasma applications such as, for example, cathodes, emissive probes, divertor plasma, surface discharges, dusty plasmas, plasma thrusters and plasma processing. In a typical low-pressure gas discharge,...
Electron hop funnels have been constructed of Low Temperature Co-fired Ceramic (LTCC) to enhance the performance of gated field emitter arrays (FEAs). Electrons are emitted into the wide end of the funnel, transmitted through the funnel, and exit through the narrow opening. An electrode, referred to here as the hop electrode, is placed around the narrow end of the funnel to create the electric field...
Numerical simulations with full representation of Coulomb effects in space-charge dominated photoemission in vacuum microdiodes indicate the presence of a mechanism leading to the formation of well-defined electron bunches corresponding to THz frequency1. We present the results of survey that examines the effects of such parameters as gap-spacing, diode voltage and electron emission velocity on the...
The challenges in developing and designing a 5 GW stand-alone pulsed power generator for driving a > 100 MW high power microwave, HPM, source are discussed. Both, applied physics aspects of operating principles and limits of the individual sub-systems will be addressed. The energy, initially provided through a set of lithium-ion batteries internal to the generator, is boosted by an explosively...
It has long been known that electron emission from a surface significantly affects the sheath at that surface.1 Typical fluid theory of a planar sheath with emitted electrons assumes that the plasma electrons follow the Boltzmann relation and the emitted electrons are emitted with zero energy and predicts a potential drop of 1.03Te across the sheath at a floating boundary. By removing the assumption...
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