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The technical challenge in constructing the electron source (ES) lies in the joining of metal and ceramic tubes. Furthermore, there is a lack of available technical comparison data for the output performance between the diode and triode ES under the same experimental conditions. The research aim is to describe a simple technique for constructing the diode and triode ES for an electron beam machine (EBM) of 300 keV/20 mA, and to investigate their output characteristics. The method used is to make a flange for mounting the Tungsten filament, Pierce electrodes, and heat shield. Two or three electrodes of the NEC (National Electric Corporation) accelerator tube are removed before the flange is united into the NEC tube, becoming the ES. The ES‘s are investigated in terms of their electron beam profiles and beam current output for the variation of the extraction electrode voltage as well as the focusing electrode voltage. The experimental results show that for the triode ES, the focusing electrode voltage greatly affects the shape of the electron beam profile up to 3 kV. However, for the diode ES, the shape of the electron beam profile is slightly affected by the extraction electrode voltage. The beam current output increases rapidly with the increase of the extraction electrode voltage up to 2.5 kV. Above this voltage, the beam current slowly increases, and it tends to reach saturation. The diode ES provides a higher electron beam current output than the triode ES output, but the triode ES provides a better shape of the electron beam profile. The constructed ES can provide the electron beam current of 40 mA at the filament current of 18 A.

Green hydrogen, produced during microalgal photosynthesis, is regarded as one of the most promising sustainable energy sources. It utilizes sunlight and water, which are essentially unlimited, and its combustion results in only water as a waste product. In microalgal hydrogen energy production systems, the sensitivity of hydrogenase to O2 poses a significant challenge, limiting sustained photosynthetic H2 production in microalgae. Additionally, efficient photosynthetic H2 production in anaerobic microalgal cells is hindered by impaired electron source (photosystem II) and electron loss through the Calvin‐Benson cycle, cyclic electron transfer around photosystem I, and O2 photoreduction, which are identified as the other key challenges. Over the past eight decades, considerable progress has been made in addressing these challenges and regulating electron transfer to achieve sustainable and efficient photosynthetic H2 production in microalgae. In this review, we discuss a range of regulatory methods for achieving sustainable and efficient photosynthetic H2 production in microalgae. Emphasizing the significant progress made over the past eight decades, we also address current challenges and propose potential future solutions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The results of experiments on the generation of a radially converging electron beam in a source with a multiarc grid plasma cathode are presented. The beam was generated at an accelerating voltage of up to 50 kV, a discharge current of 50–300 A, a pulse duration of 50–500 μs, and a pressure of 20–50 mPa. The operation modes of the electron source are compared, and the design of the plasma emitter is modernized to increase the current density to a level sufficient to modify the surface of the collector material. [ABSTRACT FROM AUTHOR]

An experimental and theoretical study is carried out to control the distribution of electron beam current density in a SOLO source with a plasma cathode based on a low-pressure arc discharge with grid stabilization of the emission plasma boundary. It has been shown experimentally and numerically that using a control electrode in the form of a disk (disks) in the plasma cathode and a leading magnetic field, it is possible to change the distribution of the emission current density and, accordingly, the energy density of the electron beam on the collector. Theoretical study using the envelope method, "particle-in-cells" method and drift-diffusion models shows good agreement with experiment. [ABSTRACT FROM AUTHOR]

On 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 new method of electron beam formation is described, in which an additional auxiliary arc discharge is ignited in the anode region of the source. Initiation of the discharge was carried out by the electron beam, and the discharge itself was supported by an additional power source, which represented a low-impedance artificial forming line included in the collector circuit. The dependence of the current in the accelerating gap on the current flowing in the collector circuit was obtained in the absence of the arc discharge current of the plasma cathode. [ABSTRACT FROM AUTHOR]

In a source based on a non-self-sustaining high-voltage glow discharge with the extraction of a large cross section electron beam (2900 cm2) 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. [ABSTRACT FROM AUTHOR]

Bright electron beams have played a critical role in many recent advances in accelerator technology. Producing bright beams via photo-emission is ultimately limited by the mean transverse energy (MTE), which is determined by the photocathode. This paper discusses the opportunity to generate bright electron beams using an upgraded version of the Argonne Wakefield Accelerator (AWA) photo-injector. The focus of this study is to examine the optimal configurations of the AWA photo-injector to produce 100 pC with a ∼100 nm transverse emittance (corresponding to a 5D brightness B 5 ≥ 10 15 A·m − 2 ). The numerical optimization of the AWA photo-injector operating point, including realistic electromagnetic field maps, is presented for the different types of photocathodes under consideration. [ABSTRACT FROM AUTHOR]

Abstract Green hydrogen, produced during microalgal photosynthesis, is regarded as one of the most promising sustainable energy sources. It utilizes sunlight and water, which are essentially unlimited, and its combustion results in only water as a waste product. In microalgal hydrogen energy production systems, the sensitivity of hydrogenase to O2 poses a significant challenge, limiting sustained photosynthetic H2 production in microalgae. Additionally, efficient photosynthetic H2 production in anaerobic microalgal cells is hindered by impaired electron source (photosystem II) and electron loss through the Calvin‐Benson cycle, cyclic electron transfer around photosystem I, and O2 photoreduction, which are identified as the other key challenges. Over the past eight decades, considerable progress has been made in addressing these challenges and regulating electron transfer to achieve sustainable and efficient photosynthetic H2 production in microalgae. In this review, we discuss a range of regulatory methods for achieving sustainable and efficient photosynthetic H2 production in microalgae. Emphasizing the significant progress made over the past eight decades, we also address current challenges and propose potential future solutions.

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 × 1012 and 1.2 × 1013 W/cm2, 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.

We conducted developmental experiments using avalanche photodiode (APD) for electron measurements applicable in future space plasma explorations. Electrons with energies of 10 eV to a hundred keV could be detected by applying "floating" voltages up to +5 kV to APD to achieve wide‐energy electron measurements. We detected 10‐eV electrons from an electron source as energized electrons of an energy of approximately 5 (5.01) keV due to the 5‐keV electrostatic acceleration (=Source energy: 0.01 keV + Acceleration energy: 5 keV; hereafter, (0.01 + 5) keV) with an energy resolution of ∼4.6 keV by simplified assumption and calculation based on peak energy and full width at half maximum of the pulse height distribution. The energy resolution for (5 + 0)‐keV electrons, ∼5.3 keV in our experiments, was equivalent to the previous results. On the other hand, we concluded that for (5 + 5) keV, the energy resolution was significantly improved to 1.3 keV compared with that for (5 + 0) keV. For (1 + 5)‐keV electrons, the energy distribution showed a broadening toward lower energies than that for (6 + 0) keV because the backscattered electrons produced secondary electrons at the APD chassis surface, which were accelerated to 5 keV by the floating voltage to be detected by the APD. We verified that the floating‐mode APD can contribute to space plasma measurements as a detector with characteristics different from those of microchannel plates. This is the first achievement to establish advanced in‐situ observation techniques based on APD for wide‐energy (a few eV to a hundred keV) electron measurements in space. Key Points: We conducted fundamental developments of floating‐mode avalanche photodiode (APD) for reducing lowermost measurable energy of electrons in spaceExperimental results indicate that the floating‐mode APD applied by +5 kV as floating voltage can detect 10‐eV electronsWe identified contaminations by secondary electrons that were produced by backscattered electrons and accelerated by the floating voltage [ABSTRACT FROM AUTHOR]

In this study, cold cathode electron sources using deep-UV photons to excite gold cathode and microchannel plate (MCP) were employed to configure a high-quality electron impact ion source (EI) in a mass spectrometry. As an electron multiplying device, MCP can amplify weak signal by thousands of times. Gold was used as a photocathode and it had the characteristics of simple excitation, stable photoemission, and uniform photocurrent density distribution. Combining the characteristics of the two, a series of research were carried out. The gold cathode JGS2 was formed by evaporation gold film on JGS2 quartz glass, and the gold-cathode MCP was formed by evaporation gold film on the input surface of MCP, respectively. The two were assembled in different combinations to develop two kinds of cold cathode electronic sources. Firstly, the deep-UV excited gold cathode MCP was used as the electron source, the output electron beam current range was 10-11-10-6 A. When the excitation light source was stable, the electron source could reach a stable state quickly and maintain a stable output for a long time (>5 h). Under the interaction of gold cathode MCP and gold cathode JGS2, the maximum output electron beam current of electron source could reach 10-5 A. At the same time, the contributions of reflected photoelectrons and transmitted photoelectrons generated by the gold cathode to the output current under different electric fields were discussed, as for the deeper working mechanism to be solved. In addition, the output electron beam current could be continuously adjusted by changing the working voltage of MCP, so that the cold cathode electron source could be flexibly and quickly adjusted and responded within a certain range. Finally, a fluorescent screen was used to observe the imaging quality of the output current generated by the above system, and the RGB image captured by the high-definition camera was converted into a grayscale image, and the non-uniformity of the image was calculated to be about 6.5%. Therefore, the imaging uniformity of the cold cathode electron source developed in this paper on the phosphor screen was good. The above results showed that the cold cathode electron source composed of gold cathode MCP excited or combined with gold cathode JGS2 by deep ultraviolet light had the characteristics of long working stability, good uniformity, wide and continuously adjustable beam current range. It can realize the functions of photoelectric conversion and electron multiplication, and is expected to provide a new alternative for the development of electron sources in EI sources in the future.

Experimental distributions of plasma parameters in the volume of a hollow cathode of a high-current non-selfsustained low-pressure glow discharge supported by electron injection from one and two electron sources located on the upper and lower bases of the cylindrical hollow cathode are obtained. A plasma source based on an arc discharge with an integrally cold hollow cathode is used as an electron source. The possibility of applying the superposition principle to predict the distribution of plasma concentration in the hollow cathode of a high-current low-pressure glow discharge with two electron sources is investigated. The distributions of the plasma parameters were measured at arc discharge currents of 20 and 45 A and glow discharge currents up to 200 A. With an increase in arc discharge currents by about 2 times, from 20 to 45 A, the accuracy of the superposition principle decreases. The maximum degree of inhomogeneity of the plasma concentration when two sources of electrons with currents of 20 A were turned on in the longitudinal direction was 25%. In the radial direction, it was 52%. The maximum discrepancy between the inhomogeneity coefficients for the experimental distribution and the distribution obtained as a result of summing the data obtained with separate operation of electron sources amounted to 8%. When two sources of electrons with currents of 45 A were switched on, the maximum inhomogeneity in the longitudinal direction was 8%, in the radial direction, it was 34%, and the maximum mismatch of the inhomogeneity coefficients was 25%. [ABSTRACT FROM AUTHOR]

A hybrid core-shell structured nanowire is proposed for a long-term stable electron source based on an isolated platinum/multi-walled carbon nanotube (Pt/MWCNT). This hybrid nanowire is prepared by growing a Pt shell on a metallic MWCNT through a field-emission-induced deposition (FEID) method. An in situ field emission (FE) platform was constructed inside a scanning electron microscope (SEM) equipped with two nanorobotic manipulators (NRMs) for the preparation and testing of the hybrid nanowire. An in situ fatigue test was conducted with high current intensity (500 nA) to show the influence of the Pt shell. Compared with the pristine bare MWCNT, our hybrid-nanowire-based electron source has a lifetime of hundreds of times longer and can work continuously for up to 48 h under relatively high pressure ( 3.6 × 10 - 3 Pa) without having an apparent change in its structure or emission currents, demonstrating good stability and tolerance to poor working conditions. The anomalous long-term stability is attributed mainly to the shielding of oxygen by Pt from the carbon shells and less heating due to the work function lowering by Pt. [ABSTRACT FROM AUTHOR]

In this study, cold cathode electron sources using deep-UV photons to excite gold cathode and microchannel plate（MCP） were employed to configure a high-quality electron impact ion source（EI） in a mass spectrometry. As an electron multiplying device, MCP can amplify weak signal by thousands of times. Gold was used as a photocathode and it had the characteristics of simple excitation, stable photoemission, and uniform photocurrent density distribution. Combining the characteristics of the two, a series of research were carried out. The gold cathode JGS2 was formed by evaporation gold film on JGS2 quartz glass, and the gold-cathode MCP was formed by evaporation gold film on the input surface of MCP, respectively. The two were assembled in different combinations to develop two kinds of cold cathode electronic sources. Firstly, the deep-UV excited gold cathode MCP was used as the electron source, the output electron beam current range was 10-11-10-6 A. When the excitation light source was stable, the electron source could reach a stable state quickly and maintain a stable output for a long time（＞5 h）. Under the interaction of gold cathode MCP and gold cathode JGS2, the maximum output electron beam current of electron source could reach 10-5 A. At the same time, the contributions of reflected photoelectrons and transmitted photoelectrons generated by the gold cathode to the output current under different electric fields were discussed, as for the deeper working mechanism to be solved. In addition, the output electron beam current could be continuously adjusted by changing the working voltage of MCP, so that the cold cathode electron source could be flexibly and quickly adjusted and responded within a certain range. Finally, a fluorescent screen was used to observe the imaging quality of the output current generated by the above system, and the RGB image captured by the high-definition camera was converted into a grayscale image, and the non-uniformity of the image was calculated to be about 6.5%. Therefore, the imaging uniformity of the cold cathode electron source developed in this paper on the phosphor screen was good. The above results showed that the cold cathode electron source composed of gold cathode MCP excited or combined with gold cathode JGS2 by deep ultraviolet light had the characteristics of long working stability, good uniformity, wide and continuously adjustable beam current range. It can realize the functions of photoelectric conversion and electron multiplication, and is expected to provide a new alternative for the development of electron sources in EI sources in the future. [ABSTRACT FROM AUTHOR]

Bright electron beams have played a critical role in many recent advances in accelerator technology. Producing bright beams via photo-emission is ultimately limited by the mean transverse energy (MTE), which is determined by the photocathode. This paper discusses the opportunity to generate bright electron beams using an upgraded version of the Argonne Wakefield Accelerator (AWA) photo-injector. The focus of this study is to examine the optimal configurations of the AWA photo-injector to produce 100 pC with a ∼100 nm transverse emittance (corresponding to a 5D brightness B5≥1015 A·m−2). The numerical optimization of the AWA photo-injector operating point, including realistic electromagnetic field maps, is presented for the different types of photocathodes under consideration.

The design of the photocathode is crucial for generating high-quality electron beam in electron sources. In this study, InGaN/GaN heterojunction nanowire photocathodes were proposed, and the photoemission theoretical model was developed. The results demonstrate that the built-in electric field along the axis enables the heterojunction nanowire photocathode to achieve higher collection efficiency across the response spectrum compared to In 0.5 Ga 0.5 N nanowire photocathodes. The variation of incidence angle results in distinct peaks in quantum efficiency and collection efficiency for the heterojunction nanowire photocathode. Meanwhile, the "additional electric field" has the potential to decrease the number of laterally emitted electrons from the nanowires, consequently reducing the shielding effect of adjacent nanowires. With an incidence angle of 15° and an "additional electric field" of 2 V/μm, the collection efficiency of photoelectrons at the collection end can be maximized to 47.6 %. This indicates that the heterojunction nanowire array photocathode has potential for use in high-performance vacuum electron sources. • The photoemission model of NEA surface InGaN heterojunction nanowire array photocathode is constructed. • The additional electric field can reduce the number of laterally emitted electrons from the nanowires. • The photocathode quantum efficiency peaks at 240 nm wavelength and an incidence angle of 15°, reaching 78.6%. [ABSTRACT FROM AUTHOR]

• The photoemission model of NEA surface InGaN tilted nanowire array photocathode is established. • The improvement of photoemission performance provides new ideas for the design of vacuum electron sources. • This paper determines the feasibility of developing the potential of nanostructured photoanodes through structural optimization, adjusting lighting conditions, and modulating the interelectrode electric field strength through simulation experiments. • The optimized tilted nanowire photoanodes, assisted by oblique light, can achieve a peak quantum efficiency of 88.35% with an electric field of 0.6 V/μm and a peak collection efficiency of 52.60% with an electric field of 4 V/μm. Photocathode has received increasing attention in scientific devices that require high-quality electron beams. A theoretical photoemission model for enhancing the performance of In 0.5 Ga 0.5 N tilted nanowire array photocathodes with negative electron affinity surface is proposed. Finite Element and finite difference methods are employed in simulation experiments to study the In 0.5 Ga 0.5 N tilted nanowire array photocathode. The results demonstrate that the photoelectric conversion performance of the In 0.5 Ga 0.5 N tilted nanowire array photocathode can be significantly enhanced through the combined impact of oblique incident light and an additional electric field. Specifically, when θ = 20°, β = −40°, and E out = 4 V/μm, the total quantum efficiency and collection efficiency are 2.79 times and 4.27 times higher than compared to vertical nanowires without external assistance, respectively. [ABSTRACT FROM AUTHOR]

The enzyme nitrogenase performs the process of biological nitrogen fixation (BNF), converting atmospheric dinitrogen gas into the biologically accessible ammonia, which is rapidly protonated at physiological pH to yield ammonium. The reduction of dinitrogen requires both ATP and electrons. Azotobacter vinelandii is an aerobic nitrogen-fixing microbe that is a model organism for the study of BNF. Previous reports have described strains of A. vinelandii that are partially deregulated for BNF, resulting in the release of large quantities of ammonium into the growth medium. Determining the source of the electrons required to drive BNF is complicated by the existence of several protein complexes in A. vinelandii that have been linked to BNF in other species. In this work, we used the high-ammonium-accumulating strains of A. vinelandii to probe the source of electrons to nitrogenase by disrupting the Rnf1 and Fix complexes. The results of this work demonstrate the potential of these strains to be used as a tool to investigate the contributions of other enzymes or complexes in the process of BNF. These results provide strong evidence that the Rnf1 complex of A. vinelandii is the primary source of electrons delivered to the nitrogenase enzyme in this partially deregulated strain. The Fix complex under native regulation was unable to provide sufficient electrons to accumulate extracellular ammonium in the absence of the Rnf1 complex. Increased ammonium accumulation could be attained in a strain lacking the Rnf1 complex if the genes of the Fix protein complex were relocated behind the strong promoter of the S-layer protein but still failed to achieve the levels found with just the Rnf1 complex by itself. Key points: • The Rnf1 complex is integral to ammonium accumulation in A. vinelandii. • The Fix complex can be deleted and still achieve ammonium accumulation in A. vinelandii. • A. vinelandii can be engineered to increase the contribution of the Fix complex to ammonium accumulation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

[Display omitted] Field-induced electron emission offers the best performance point electron source for electron microscopes. Herewith we report a new cold field-emission point electron source utilizing a nanoneedle made of lanthanum hexaboride (LaB 6) and its implementation in a spherical aberration-corrected transmission electron microscope (TEM). A sub-ångstrom resolution of 0.96 Å has been obtained with the TEM operated at an acceleration voltage of 60 kV and a smaller energy spread was also observed compared with the contemporary W(310) electron source. In particular, the LaB 6 nanoneedle cold field-emission electron source required no thermal flashing for continuous operation of extended hours (>100 hours) while exhibiting and sustaining a high stability in emission current (<1%). We attribute the excellent performance of the LaB 6 nanoneedle electron source to (i) a low work function of LaB 6 ; (ii) excellent alignment of the nanoneedle emitter by the electron and ion dual-beam processing with nanoscale precision and (iii) robustness of the nanometric structure that suppressed mechanical vibrations of the LaB 6 emitter even in a high electric field. This new LaB 6 nanoneedle cold field-emission electron source enables stable high-resolution imaging in TEM and it will also benefit cryogenic electron microscopy, scanning electron microscopy, electron beam lithography, and other electron beam technologies. [ABSTRACT FROM AUTHOR]

A hybrid core-shell structured nanowire is proposed for a long-term stable electron source based on an isolated platinum/multi-walled carbon nanotube (Pt/MWCNT). This hybrid nanowire is prepared by growing a Pt shell on a metallic MWCNT through a field-emission-induced deposition (FEID) method. An in situ field emission (FE) platform was constructed inside a scanning electron microscope (SEM) equipped with two nanorobotic manipulators (NRMs) for the preparation and testing of the hybrid nanowire. An in situ fatigue test was conducted with high current intensity (500 nA) to show the influence of the Pt shell. Compared with the pristine bare MWCNT, our hybrid-nanowire-based electron source has a lifetime of hundreds of times longer and can work continuously for up to 48 h under relatively high pressure (3.6×10-3 Pa) without having an apparent change in its structure or emission currents, demonstrating good stability and tolerance to poor working conditions. The anomalous long-term stability is attributed mainly to the shielding of oxygen by Pt from the carbon shells and less heating due to the work function lowering by Pt.

A miniaturized radio frequency (RF) excited grid-free field emission cathode made by single-wall carbon nanotubes (SWCNTs) is suggested and studied. The $\lambda $ /4 coaxial resonant cavity is used as field-emitted electron source with length of 26.5 mm and diameter of 12.8 mm. Electrons can be pulled out by a small electrostatic field and an RF electric field without interception. The RF electric field of inner conductor surface at the open end, which pasted SWCNTs, can reach 3 MV/m when the input power is 30 W, and the field is larger than the turn-on field of SWCNTs. The results of simulation and experiment both show that the maximum emission current under input RF power of 30 W is 30 times larger than without RF excitation, which can reach 24 mA at the anode voltage of 950 V. This miniaturized RF excited grid-free field emission cathode electron source can be used as electron source, in a high repetition frequency vacuum electronic devices, e.g., terahertz (THz) devices, and X-ray tubes. [ABSTRACT FROM AUTHOR]

We describe a method for dynamic power control of a submillisecond pulsed electron beam in a "SOLO" type source with plasma cathode. The beam power is controlled by dynamic variation of the beam current amplitude with the corresponding low-inertia change in the concentration of emissive plasma. This method can be used to generate submillisecond electron beams of variable power (up to 10 MW at a maximum variation rate not exceeding 0.5 W/μs)—in particular, for the processing of various metallic materials with modification of their functional properties by controlled beam energy supply to the material surface. [ABSTRACT FROM AUTHOR]

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.

On-chip tunneling electron sources have wide potential applications in miniature vacuum electronic devices, and emission efficiency is one of their performance benchmarks. A cascade electron source (CES) based on series metal–insulator–metal horizontal tunneling junctions (HTJs) is proposed, where free electrons are additively extracted from each tunneling junction. A CES with ${n}$ HTJs shows a theoretical emission efficiency of approximately η(n) = 1-(1-η0)n, with η0 being the efficiency of a single tunneling junction. Experimentally, a CES with three Si–SiOx–Si tunneling junctions is demonstrated, achieving an emission efficiency of as high as 47.6%. This work provides a new way of realizing highly efficient on-chip tunneling electron sources. [ABSTRACT FROM AUTHOR]

With the growing demand from scientific projects such as the X-ray free electron laser (XFEL), ultrafast electron diffraction/microscopy (UED/UEM) and electron ion collider (EIC), the semiconductor photocathode, which is a key technique for a high brightness electron source, has been widely studied in China. Several fabrication systems have been designed and constructed in different institutes and the vacuum of most systems is in the low 10−8 Pa level to grow a high QE and long lifetime photocathode. The QE, dark lifetime/bunch lifetime, spectral response and QE map of photocathodes with different kinds of materials, such as bialkali (K2CsSb, K2NaSb, etc.), Cs2Te and GaAs, have been investigated. These photocathodes will be used to deliver electron beams in a high voltage DC gun, a normal conducting RF gun, and an SRF gun. The emission physics of the semiconductor photocathode and intrinsic emittance reduction are also studied.

To date, lanthanum hexaboride (LaB6) thermionic electron sources have not been able fully to capitalize on their inherent potential, resulting in an ambiguous position within the application area. Although they exhibit higher brightness compared with a tungsten filament source, they still fall short of the performance of Schottky electron sources. This study aims to explore the capabilities of the LaB6 electron source under different operating conditions to bridge the gap, ultimately to realize its untapped potential. Simulations in virtual source mode indicated enhanced beam brightness and a reduced beam half-angle with an increase the extraction voltage, promising up to tenfold times higher beam brightness compared with the crossover mode. The energy distribution measured using a prelens retarding field energy analyzer revealed an energy distribution of 0.55 eV and a high angular current density of 33 mA/sr in the virtual source mode. Therefore, the virtual source mode of LaB6 can provide a narrow energy distribution akin to that of a ZrO/W Schottky electron gun (1600 K) while having an angular current density over 2,000 times higher. In addition, the stability of the virtual source mode is ±0.022%, while that of the crossover mode is ±0.138%., Competing Interests: Conflict of Interest The authors declare that they have no competing interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Microscopy Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)