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Motivated by recent progress in electron quantum optics, we revisit the question of single-electron entanglement, specifically whether the state of a single electron in a superposition of two separate spatial modes should be considered entangled. We first discuss a gedanken experiment with single-electron sources and detectors, and demonstrate deterministic (i. e. without post-selection) Bell inequality violation. This implies that the single-electron state is indeed entangled and, furthermore, nonlocal. We then present an experimental scheme where single-electron entanglement can be observed via measurements of the average currents and zero-frequency current cross-correlators in an electronic Hanbury Brown-Twiss interferometer driven by Lorentzian voltage pulses. We show that single-electron entanglement is detectable under realistic operating conditions. Our work settles the question of single-electron entanglement and opens promising perspectives for future experiments.

The development of dynamic single-electron sources has made it possible to observe and manipulate the quantum properties of individual charge carriers in mesoscopic circuits. Here, we investigate multi-particle effects in an electronic Mach–Zehnder interferometer driven by a series of voltage pulses. To this end, we employ a Floquet scattering formalism to evaluate the interference current and the visibility in the outputs of the interferometer. An injected multi-particle state can be described by its first-order correlation function, which we decompose into a sum of elementary correlation functions that each represent a single particle. Each particle in the pulse contributes independently to the interference current, while the visibility (given by the maximal interference current) exhibits a Fraunhofer-like diffraction pattern caused by the multi-particle interference between different particles in the pulse. For a sequence of multi-particle pulses, the visibility resembles the diffraction pattern from a grid, with the role of the grid and the spacing between the slits being played by the pulses and the time delay between them. Our findings may be observed in future experiments by injecting multi-particle pulses into a Mach–Zehnder interferometer.

Using the example of an electron source with a plasma cathode based on a low-pressure arc discharge with grid stabilization of the cathode/emission plasma boundary and an open anode/beam plasma boundary, a mechanism is described for increasing the electrical strength of a high-voltage accelerating gap by introducing a series negative current feedback (NCF) in the accelerating interval, which makes it possible to level out uncontrolled bursts of the beam current during its pulse. The introduction of NCF is achieved by using a special electrode in the space of the plasma emitter connected through a resistance to the anode of the arc discharge, and the main task of which is to intercept accelerated ions penetrating into the emitter from the high-voltage accelerating gap, due to which the current of electron emission from the arc discharge plasma decreases by a value proportional to the ion current in the accelerating gap. Since most sources and accelerators of electrons with plasma cathodes based on discharges of various types have a similar principle of operation, the use of this method will not only expand the limiting parameters of the generated electron beams, but also increase the stability of the operation of such electron sources, and, accordingly, beam irradiation of various materials and products.

This is a review of current developments in the field of ion-plasma and beam methods of synthesis of protective and functional dielectric coatings. We give rationales for attractiveness and prospects of creating such coatings by electron-beam heating and following evaporation of dielectric targets. Forevacuum plasma electron sources, operating at elevated pressure values from units to hundreds of pascals, make it possible to exert the direct action of an electron beam on low-conductive materials. Electron-beam evaporation of aluminum oxide, boron, and silicon carbide targets is used to exemplify the particular features of electron-beam synthesis of such coatings and their parameters and characteristics.

We investigated the generation and control of fast photoelectrons (PEs) by exposing plasmonic nanoparticles (NPs) to short infrared (IR) laser pulses with peak intensities between 10 and 3 × 10  W/cm . Our measured and numerically simulated PE momentum distributions demonstrate the extent to which PE yields and cutoff energies are controlled by the NP size, material, and laser peak intensity. For strong-field photoemission from spherical silver, gold, and platinum NPs with diameters between 10 and 100 nm our results confirm and surpass extremely high PEs cutoff energies, up to several hundred times the incident laser-pulse ponderomotive energy, found recently for gold nanospheres [Saydanzad et al., Nanophotonics , 1931 (2023)]. As reported previously for dielectric NPs [Rupp et al., J. Mod. Opt. , 995 (2017)], at higher intensities the cutoff energies we deduce from measured and simulated PE spectra tend to converge to a metal-independent limit. We expect these characteristics of light-induced electron emission from prototypical plasmonic metallic nanospheres to promote the understanding of the electronic dynamics in more complex plasmonic nanostructures and the design of nanoscale light-controlled plasmonic electron sources for photoelectronic devices of applied interest.

In a source based on a non-self-sustaining high-voltage glow discharge with the extraction of a large cross section electron beam (2900 cm 2 ) into the atmosphere, the dynamics of the anode plasma during the generation period of an auxiliary glow wire discharge with a hollow cathode is demonstrated. A repetitively pulsed generation mode with a frequency of 10 kHz was used. The features of the formation and evolution of the auxiliary discharge anode plasma were studied by measuring the distribution of the electron beam current density in the atmosphere. By applying a negative potential bias to the anode grid by (50–200 V) relative to the walls of the vacuum chamber, the possibility of increasing the electron beam extraction coefficient into the atmosphere during the discharge generation pause is shown. New modes of electron beam generation and its more efficient extraction into the atmosphere open new prospects for using electron sources of this type both in science and in industrial applications.

The development of pulsed electron sources is applied to electron microscopes or electron beam lithography and is effective in expanding the functions of such devices. The laser photocathode can generate short pulsed electrons with high emittance, and the emittance can be increased by changing the cathode substrate from a metal to compound semiconductor. Among the substrates, nitride-based semiconductors with a negative electron affinity (NEA) have good advantages in terms of vacuum environment and cathode lifetime. In the present study, we report the development of a photocathode electron gun that utilizes photoelectron emission from a NEA-InGaN substrate by pulsed laser excitation, and the purpose is to apply it to material nanofabrication and high-speed observation using a pulsed transmission electron microscope (TEM) equipped with it.

Recent discoveries in the field of nanoscale vacuum channel (NVC) structures have led to potential on-chip electron sources. However, limited research has reported on the structure or material parameters, and the superiority of a nanoscale vacuum channel in an electron source has not been adequately demonstrated. In this paper, we perform the structural optimization design of an NVC-based electron source. First, the structure parameters of a vertical NVC-based electron source are investigated. Moreover, the symmetrical NVC structure is further demonstrated to improve the emission current and effective electron efficiency. Finally, a symmetrical nano-vacuum channel structure is successfully fabricated based on simulations. The results show that the anode current exceeds 15 nA and that the effective electron efficiency exceeds 20%. Further miniaturizing the NVC structures in high integration can be utilized as an on-chip electron source, thereby, illustrating the potential in applications of electron microscopes, miniature X-ray sources and on-chip traveling wave tubes.

The efficient generation, accurate detection, and detailed physical tracking of energetic electrons are of applied interest for high harmonics generation, electron-impact spectroscopy, and femtosecond time-resolved scanning tunneling microscopy. We here investigate the generation of photoelectrons (PEs) by exposing plasmonic nanostructures to intense laser pulses in the infrared (IR) spectral regime and analyze the sensitivity of PE spectra to competing elementary interactions for direct and rescattered photoemission pathways. Specifically, we measured and numerically simulated emitted PE momentum distributions from prototypical spherical gold nanoparticles (NPs) with diameters between 5 and 70 nm generated by short laser pulses with peak intensities of 8.0 × 10 and 1.2 × 10  W/cm , demonstrating the shaping of PE spectra by the Coulomb repulsion between PEs, accumulating residual charges on the NP, and induced plasmonic electric fields. Compared to well-understood rescattering PE cutoff energies for strong-field photoemission from gaseous atomic targets (10× the ponderomotive energy), our measured and simulated PE spectra reveal a dramatic cutoff-energy increase of two orders of magnitude with a significantly higher contribution from direct photoemission. Our findings indicate that direct PEs reach up to 93 % of the rescattered electron cutoff energy, in contrast to 20 % for gaseous atoms, suggesting a novel scheme for the development of compact tunable tabletop electron sources.

In this review, several types of plasma electron sources, studied in the Plasma Physics and Pulsed power Laboratory during the last 20 years, are considered. Namely, main parameters, such as plasma density and temperature, expansion velocity and plasma uniformity, life-time and vacuum compatibility of passive plasma cathodes (explosive emission cathodes, metal ceramic, velvet, carbon fiber with and without CsI coating, carbon capillary, and multi-capillary and multi-slot) and active plasma cathodes (ferroelectric and hollow anodes) are described and discussed. These parameters were studied and characterized using different timeand space-resolved electrical, optical, spectroscopic, Thomson scattering, Laser Induced Fluorescence and Xray diagnostics. It was shown that the operation of passive sources is governed by the formation of flashover plasma whose parameters depend on the amplitude and rise time of the accelerating electric field. In the case of ferroelectric and hollow-anode plasma sources, the plasma parameters are controlled by the driving pulse and discharge current, respectively. In addition, parameters of high-current electron beams generated in high voltage and high current electron diodes with these plasma cathodes are presented.