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An effective design for cold cathode named as the interdigitated field electron emission driving-secondary electron emission (FEE-SEE) cathode is proposed in this article. The cathode consists of an FEE region and an SEE region, which integrates the advantages of the field emission and secondary emission on the M-type device. The excellent FEE performance of the directional single-wall carbon nanotubes (SWCNTs) with an effective method of directly imprinting the SWCNTs sludge on a substrate is studied for obtaining higher primary excitation current. Meanwhile, the cathode prebunch technique is implemented by imposing a fivefold azimuthal variation on the SEE cathode of a ten-cavity magnetron, which could prebunch the electrons into the desired mode at birth to enhance stability and speed startup time. A 3-D particle-in-cell simulation analysis is used to predict a novel cold cathode magnetron with high output power of 3144 W with 6.2% efficiency enhancement with reference to the conventional thermionic cathode applied to the 2450-MHz magnetron. Its startup time is about 100 ns with excellent stability and pure output spectrum.

This article presents an experimental investigation of microwave breakdown in evanescent-mode cavity resonators with different surface materials and post geometries, aiming at unveiling the role of secondary electron emission (SEE), attachment, and diffusion on microwave breakdown in inhomogeneous electric fields. The breakdown power of six cavities resonating at 2.6 GHz was measured at pressures ranging from 1 to 100 mbar in ambient air. The cavity with lower secondary emission yield surface material has a higher breakdown power on the left side of the breakdown curves, indicating the importance of SEE in microwave breakdown, especially at low pressures. Meanwhile, except for the cavity with hemisphere post, it was found that the quality factor has little effect on the breakdown power since electric field distributions inside these cavities are not significantly linked to post geometry. Two distinct regimes are observed in the breakdown curves with a transition pressure of 10 mbar. Namely, the breakdown curves present an emission-free branch above the transition, where microwave breakdown occurs in the gap, and a diffusion branch below the transition, where the microwave plasma expands out of the gap. We performed a theoretical calculation and found that the transition occurs when the attachment length equals the post radius.

High-gradient insulators (HGIs) are materials created by alternating layers of insulating and conducting materials, which can result in a higher holdoff voltage than a monolithic insulator of the same length. We model the HGIs periodic electric field and use both a particle-in-cell direct simulation Monte Carlo code and a test particle approach to parameterize the growth of the secondary electron emission avalanches (SEEAs). To determine the effect of various HGI design parameters on secondary electron trajectories and SEEA growth, the following factors are investigated: layer width, edge layer materials, secondary electron yield, cell coupling, and surface defects as an electron source. We propose an alternative mechanism for initiating surface flashover, which considers surface defects on the downstream side of insulating layers, which differs from the current theory of cell coupling between adjacent insulating layers. Our results indicate surface conditioning is necessary because surface defects are a significant electron source in many cases. Our results reinforce the theory that thin layer widths are better at minimizing the growth of a surface avalanche, even though they will be more susceptible to cell coupling. If an HGI will not be conditioned prior to use, then thin layers are essential because of the significant avalanche growth capable along thicker layers. Finally, a metal layer adjacent to the cathode and an insulating layer adjacent the anode seems the optimal configuration to minimize the probability of flashover.

In 1982, Capasso and co-workers proposed the solid-state analogue of the photomultiplier tube, termed the staircase avalanche photodiode. Through a combination of compositional grading and small applied bias, the conduction band profile is arranged into a series of steps that function similar to the dynodes of a photomultiplier tube, with twofold gain arising at each step via impact ionization. A single-step staircase was previously reported but did not demonstrate gain scaling through cascading multiple steps or report noise properties. Here we demonstrate gain scaling of up to three steps; measurements show the expected 2N scaling with the number of staircase steps, N. Furthermore, measured noise increased more slowly with gain than for photomultiplier tubes, probably due to the lower stochasticity of impact ionization across well-designed heterojunctions as compared with the secondary electron emission from metals. Excellent agreement was found between the experiments and Monte Carlo simulations for both gain and noise. A three-step staircase avalanche diode was demonstrated and pre-cited gain scaling was confirmed. The technology may be considered as a solid-state analogue to the photomultiplier tube.

The main features of the secondary emission mass spectrometry probing of condensed systems containing compounds of biological significance at low temperatures are summarized. The possibilities of distinguishing mass spectra of the solid and liquid phases of simple organic compounds and water as the medium for bio-molecules, monitoring of phase transitions and nonequilibrium processes are illustrated. The peculiarities of a model of sputtering of metastable liquids are described. On the basis of the evaluation of these findings, an idea concerning the probable source of relatively large clusters of organic molecules and ions emerging on sputtering of the liquid phase of organic matter condensed on dust grains in space is proposed and discussed.

As a secondary electron emission layer, an Al2O3/MgO double-layer structure is fabricated by atomic layer deposition (ALD) technology. The thickness range from 1 nm to 4 nm of the top Al2O3 layer deposited on 20 nm MgO creates a double-layer. The morphology of the cross section, element distribution, surface roughness, X-ray diffraction, and secondary electron yield (SEY) values were measured by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM) and secondary electron emission (SEE) measurement systems. The SEE characteristics of the MgO single layer, Al2O3 single layer and MgO/Al2O3 double-layer were measured. The maximum SEY of a single MgO layer reached 6.2@600 eV, and the maximum SEY of a single Al2O3 layer reached 3.92@400 eV. The SEY of the Al2O3/MgO double-layer decreased when the Al2O3 thickness ranged from 1 nm to 4 nm, and the SEY reduction value of the double-layer decreased as the Al2O3 thickness increased. Finally, Dionne's semiempirical SEE model was employed to explain the SEE yield of the prepared composite film structures. These results are useful for depositing a secondary electron emission layer in the channel of microchannel plates.

The cathode in the magnetron should have good secondary emission property and a certain thermionic property. In this article, ZrH2 was added as an activator to obtain rare earth-doped tungsten matrix impregnated cathode to improve the emission property. Cathodes with ZrH2 (Y15-411-Zr cathode) or without ZrH2 (Y15-411 cathode) were prepared by a spray drying method combined with high-temperature sintering in dry hydrogen atmosphere. The emission properties and emission mechanism have been studied. The results showed that thermionic emission performance and secondary emission performance of Y15-411-Zr cathode are 3.4 times and 1.2 times higher than those of Y15-411 cathode, respectively. With the addition of ZrH2, yttrium was produced during activating process, which contributed to the better emission properties of Y15-411-Zr cathode. Furthermore, the work function of barium and oxygen adsorbed on yttrium oxide and yttrium surface was calculated using the first principle. The results showed that the lowest work function of Ba-O absorbed on Y2O3 and Y is 1.9 and 1.6 eV, respectively.

The results of kinetic modeling by the Monte Carlo method of sputtering heavy d-metals of Ir, Os, and W group by nitrogen N+ ions with energy in the range of 0.5–2.5 keV are presented. The coefficients of physical ion sputtering, the average sputtered atom energies, the reflection coefficients of the bombarding ions in the form of neutral nitrogen atoms, and the depth of ion penetration into the target were calculated. The calculations were performed for one-, two- and three-element targets, the partial ion sputtering coefficients of these metals were determined, and the influence of the surface binding energy on the ion sputtering parameters of individual target elements was studied. The calculations were performed for an Al target to compare the ion sputtering parameters of heavy d-metals and light aluminum. Despite the strong difference between the surface binding energy for these metals, their sputtering coefficients are of the same order of magnitude due to the fact that nitrogen ions penetrate deeper into aluminum and the exit of the recoil atoms from the target is impeded. The reflected or backscattered neutralized nitrogen atoms represent the second type of atomic particles emitted from the target. The coefficients of reflection of the bombarding nitrogen particles from the heavy metals and aluminum are determined.

This letter proposed a combined susceptibility diagram, applicable to investigating and differentiating the inherent mechanism of multipactor in dielectric-loaded microwave devices. This susceptibility diagram consists of average secondary emission yield on the dielectric surface and both the surfaces. Using this diagram, we predict the electron multiplication mechanism in the partially dielectric-loaded parallel-plate waveguide. It is found that the multipactor extinguishing only occurs for a low multipaction rate, while the saturation occurs for a higher multipaction rate. To verify its validity, the dynamic evolution of multipactor is investigated by electrostatic particle-in-cell. A good agreement between simulations and prediction results has been achieved. This susceptibility diagram thus constructed can provide a guidance to clearly identify the condition for multipactor extinguishing or saturation.

Nanoscale MoO3 films are obtained on the surface of a Mo single crystal by means of thermal oxidation and ion implantation. The optimal modes of ion implantation (the partial oxygen pressure, the ion energy and dose, and the annealing temperature) are determined to form homogeneous MoO3/Mo films with thicknesses ranging from 30 to 100 A and with good stoichiometry. It is established that, for low doses of oxygen ions (D ≤ 1016 cm–2), nanoscale MoO3 phases form on the Mo-crystal surface. The dependence of the degree of Mo surface coverage by MoO3 cluster phases on the ion dose is determined. Films with a thickness of ~100 A are obtained by successively implanting $${\text{O}}_{2}^{ + }$$ ions with energies of 5, 3, and 1 keV. The composition, the electronic structure, and the emission and optical properties of the nanoscale phases and MoO3 films are studied using a complex of methods (Auger- and photoelectron spectroscopy, secondary electron emission, and secondary-ion mass spectroscopy).