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We here report on the development of an improved dual-gridded electron gun based on a carbon nanotube cold cathode that enhances electron beam transparency and reduces grid interception and loss pathways. Compared with microscale tip Spindts, the dual-gridded construction decreases challenges associated with nanomaterial growth, fabrication, and assembly. Our experimental findings show that this dual-gridded CNT electron gun can support anode output currents (cathode emission current) of up to 700 mA, with a beam-transparency of up to ~100% and a compression ratio of 1/19. A beam spot of uniform brightness is obtained and the radius of the beam spot is 1.5 mm. In addition, our studies show that the device can operate at 1/100 duty cycle continuous pulse with a stable current of around 100mA over 100 h.

To improve the performance of a pencil beam electron gun for terahertz traveling wave tubes (TWT), a support vector regression (SVR) method combined with a goal attainment algorithm, which is used to optimize its structural parameters considering the periodic permanent magnetic (PPM) focusing system, is proposed in this article. Moreover, a parameter correction method to reduce the impact of the thermal expansion on the electron gun is proposed. An electron gun for 0.22-THz TWT gun is developed, in which a 30-mA/23.8-kV electron beam emitted by a curved barium-tungsten cathode with a beam loading of 4 A/cm² is achieved with the optimized parameters. To the high current density for THz beam-wave interaction, the area compression ratio of electron beam is used in beam tunnel and reaches 144. The experimental results are very similar to the simulation results, which indicate that the methods would be beneficial to the development of TWT.

The CeB6(001) single crystal used as a cathode in a low-emittance electron gun and operated at the free-electron laser facility SACLA was investigated using cathode lens electron microscopy combined with X-ray spectroscopy at SPring-8 synchrotron radiation facility. Multilateral analysis using thermionic emission electron microscopy, low-energy electron microscopy, ultraviolet and X-ray photoemission electron microscopy and hard X-ray photoemission spectroscopy revealed that the thermionic electrons are emitted strongly and evenly from the CeB6 surface after pre-activation treatment (annealing at 1500°C for >1 h) and that the thermionic emission intensity as well as elemental composition vary between the central area and the edge of the old CeB6 surface.

A planar distributed three-beam electron optics system with narrow beam separation is investigated in this article for W-band fundamental-mode staggered double vane traveling wave tube (TWT). An integrated electron gun with control electrode for planar distributed three-beam array has been constructed based on the grid loaded method, which is a general method to obtain planar multibeam array by 1-D compression. Then, the uniform magnetic focusing system is constructed for planar distributed three-beam array, where the peak value of axial magnetic field ${B}_{z}$ can be achieved 4600 Gs. The pole piece with novel stepped hole is considered in this magnet system, which can reduce the transverse magnetic field disturbance effectively. The optimization of the magnet structure and magnetic saturation analysis of the pole piece is fully considered to ensure the transmission stability of the three-beam array and reduce the volume of the whole system. The simulation results show that the three-beam array can transmit 70 mm with the transmission rate of 100% under the uniform magnetic focusing system. The whole system stability is verified, including the assembly error, working voltage fluctuations, and variations of magnetic field. The designed electron optics system can be used for the fundamental-mode staggered double vane traveling wave tube in W-band to improve the high output power in future.

Highly charged ion sources play an important role in the advancement of heavy-ion accelerators worldwide. Demands of highly charged heavy ions for new and existing accelerators have driven the performance of ion sources to their limits. A new high charge state ion accumulating trap concept is proposed that converts a dc ion beam from an electron cyclotron resonance (ECR) ion source into a short-pulsed ion beam with suitable compression ratios. With a simple trap composed of an electron gun, a solenoid, and a set of drift tubes (DTs), the injected ions from a dc operation ECR ion source will be trapped radially and axially. By manipulating the potential of the DT, highly charged ions can be accumulated with multiple injections and extracted with augmentation of ion intensity in pulses of tens of $\mu \text{s}$ . This article presents the simulations and design features of the envisioned ion trap.

Although scanning transmission electron microscopy (STEM) images of individual heavy atoms were reported 50 years ago, the applications of atomic-resolution STEM imaging became wide spread only after the practical realization of aberration correctors on field-emission STEM/TEM instruments to form sub-Ångstrom electron probes. The innovative designs and advances of electron optical systems, the fundamental understanding of electron–specimen interaction processes, and the advances in detector technology all played a major role in achieving the goal of atomic-resolution STEM imaging of practical materials. It is clear that tremendous advances in computer technology and electronics, image acquisition and processing algorithms, image simulations, and precision machining synergistically made atomic-resolution STEM imaging routinely accessible. It is anticipated that further hardware/software development is needed to achieve three-dimensional atomic-resolution STEM imaging with single-atom chemical sensitivity, even for electron-beam-sensitive materials. Artificial intelligence, machine learning, and big-data science are expected to significantly enhance the impact of STEM and associated techniques on many research fields such as materials science and engineering, quantum and nanoscale science, physics and chemistry, and biology and medicine. This review focuses on advances of STEM imaging from the invention of the field-emission electron gun to the realization of aberration-corrected and monochromated atomic-resolution STEM and its broad applications.

Purpose Recently, high-precision radiotherapy systems have been developed by integrating computerized tomography or magnetic resonance imaging to enhance the precision of radiotherapy. For integration with additional imaging systems in a limited space, miniaturization and weight reduction of the linear accelerator (linac) system have become important. The aim of this work is to develop a compact medical linac based on 9.3 GHz X-band RF technology instead of the S-band RF technology typically used in the radiotherapy field. Methods The accelerating tube was designed by 3D finite-difference time-domain and particle-in-cell simulations because the frequency variation resulting from the structural parameters and processing errors is relatively sensitive to the operating performance of the X-band linac. Through the 3D simulation of the electric field distribution and beam dynamics process, we designed an accelerating tube to efficiently accelerate the electron beam and used a magnetron as the RF source to miniaturize the entire linac. In addition, a side-coupled structure was adopted to design a compact linac to reduce the RF power loss. To verify the performance of the linac, we developed a beam diagnostic system to analyze the electron beam characteristics and a quality assurance (QA) experimental environment including 3D lateral water phantoms to analyze the primary performance parameters (energy, dose rate, flatness, symmetry, and penumbra) The QA process was based on the standard protocols AAPM TG-51, 106, 142 and IAEA TRS-398. Results The X-band linac has high shunt impedance and electric field strength. Therefore, even though the length of the accelerating tube is 37 cm, the linac could accelerate an electron beam to more than 6 MeV and produce a beam current of more than 90 mA. The transmission ratio is measured to be approximately 30% ~ 40% when the electron gun operates in the constant emission region. The percent depth dose ratio at the measured depths of 10 and 20 cm was approximately 0.572, so we verified that the photon beam energy was matched to approximately 6 MV. The maximum dose rate was measured as 820 cGy/min when the source-to-skin distance was 80 cm. The symmetry was smaller than the QA standard and the flatness had a higher than standard value due to the flattening filter-free beam characteristics. In the case of the penumbra, it was not sufficiently steep compared to commercial equipment, but it could be compensated by improving additional devices such as multileaf collimator and jaw. Conclusions A 9.3 GHz X-band medical linac was developed for high-precision radiotherapy. Since a more precise design and machining process are required for X-band RF technology, this linac was developed by performing a 3D simulation and ultraprecision machining. The X-band linac has a short length and a compact volume, but it can generate a validated therapeutic beam. Therefore, it has more flexibility to be coupled with imaging systems such as CT or MRI and can reduce the bore size of the gantry. In addition, the weight reduction can improve the mechanical stiffness of the unit and reduce the mechanical load.

Purpose The purpose of this study was to deposit Bi4Ti3O12 films by electron gun evaporation technique starting from Bi3.25La0.75Ti3O12 as a target without annealing. The films have been deposited on Si(100), on thin film buffer layer of Pt and glass substrates. X-ray diffraction (XRD) was used to analyze structure of the films, which possesses a good structure with (0010) preferred orientation. Electronic behavior of the samples has been studied. Design/methodology/approach The dependence of both the structure and quality of the BLT thin films on different substrates is studied using XRD. The electrical characteristics were determined using capacitance–voltage (C–V) and current–voltage (I–V) measurements at the frequency of 1 MHz. Optical properties of the grown films deposited on glass substrates were characterized by optical transmittance measurements (UV-Vis). Findings The XRD analysis approved the crystallographer structure of the prepared Bi4Ti3O12 films. The optical properties of deposited film (transmittance and the band gap value) are extracted by UV-Vis spectrum. Originality/value High crystalline quality Bi4Ti3O12 films have been obtained using different substrates at room temperature by means of electron gun deposition. The electrical and ferroelectric properties of thin films were studied using I–V and C–V measurements. The band gap has been found to be about 3.62 eV for the studied film deposited on glass substrate. Electron beam evaporation technique is the most interesting methods, once considering many advantages; such as its stability, reproducibility, high deposition rate and the compositions of the films are controlled.

The electron beam of a ${K}$ -band space traveling-wave tube (TWT) has been investigated in a beam measurement system in this article. The primary beam emitted from a Pierce-type electron gun is scanned by a Faraday cup probe, and the beam current density distribution and envelope are determined. The spent beam is also diagnosed with a novel retarding field energy analyzer (RFEA) by using the monopulse measurement method, and a comparison of velocity distribution between the experimental result and simulation is presented.

In this article, a trigger unit has been implemented to generate a high-current-density electron beam from a pseudospark (PS) discharge-based electron gun. A trigger pulse power supply unit has been designed and developed to provide the seed electrons from the ferroelectric cathode (FEC). The FEC has been used inside the hollow cathode cavity of a single-gap PS discharge-based electron gun. The electron gun has been operated in the self-breakdown as well as the trigger-based breakdown mode. A comparative analysis has also been performed between self-breakdown and trigger breakdown modes with the developed trigger unit’s help for different applied gap voltages ranging between 0 and 16 kV. The designed trigger unit is based on a high-voltage-gain isolated dc–dc converter and a pulse-forming network. It is compact and capable of generating a negative pulse of ~–5 kV with a pulsewidth of ~500 ns. It provides better control over PS discharge to produce a high-current-density electron beam.

The 220-GHz continuous wave (CW) folded waveguide (FWG) traveling wave tube (TWT) is presented as the high-power amplifier for the terahertz (THz) communication system in this article. This tube is designed and fabricated including FWG circuit, electron gun, periodical permanent magnet system, coupling window, and thermal management structure. The test results show that with the pencil beam of 20.5 kV and 52.4 mA, the output power is 16 W and the corresponding bandwidth is 7 GHz from 213 to 220 GHz, and the maximum power and the corresponding gain are 30 W and 31.2 dB at the frequency of 217 GHz.

We present experimental characterization of a 20-kV, 130-mA thermionic electron gun, which is a component of a ${W}$ -band traveling-wave tube (TWT) power amplifier. The electron beam is strongly focused by a 6.6-kG permanent magnet solenoid, producing a peak current density up to 800 A/cm2. The cathode temperature, focus electrode voltage, and modulating anode voltage are varied to characterize the emitted cathode current and beam transport through the beam tunnel of the TWT RF circuit. We observe the variation of the cathode current from 107 to 155 mA and peak beam transmission of 95% measured at the collector. Experimental results are compared to 2-D simulations with the electron gun and collector design code MICHELLE.

Field emission cathode electroluminescent lamp is a light source with multiple advantages including continuous light spectrum and high efficiency. However, it needs a high operation voltage of the order of kilovolts with transformer, because its emitters have limited cathode - anode distance at hundreds of microns and high operation electric field. This study makes graphene and carbon nanotubes (CNTs) hybrid field electron emitter with ultra-low turn-on field down to 0.1 V/μm. Their diode-structure field emission lamp can be directly driven by 110 V and 220 V household electricity supply and has bright luminescence with a very low power consumption of 14 mW. The emitters are made of alternated graphene/CNTs sandwich material, and their good field emission properties are attributed to these alternated graphene layers. During field emission, the graphene layers switch their function as spacers to reduce the screening effect at low operation field and also participate in electron emission at high operation field. This study offers a new strategy to make low power consumption and healthy light sources. Meanwhile, this study also raises the requirement to develop low voltage and high efficiency electronic luminescent phosphor.

The results of a theoretical study of a high power W-band extended interaction klystron with a hollow electron beam are presented. Numerical studies were carried out using the PARS computer code, taking into account the thermal spread of electron velocities at the cathode. As a result of the research and optimization of the parameters, the design of the electron-optical system and the interaction system of the 6-cavity klystron was developed, which provides a record output power of 8.6 kW for a given frequency with a gain of 56 dB, an electronic efficiency of 32 $$\%$$ and a full efficiency of 26 $$\%$$ . Using the developed two-stage depressed collector with a recovery efficiency of 54 $$\%$$ in dynamic mode, it is possible to provide the full efficiency of the device at the level of 40 $$\%$$ . The results of numerical calculations of the dynamics of electrons and their interaction with electromagnetic fields from the cathode to the collector in the quasi-three-dimensional approximation are presented.

State-of-the-art electrodynamic tethers reach a steady electric current by using a bare segment to capture electrons passively from the ambient plasma (anodic contact) and an active electron emitter or a tether segment coated with a low-work-function material (cathodic contact) to emit electrons back and close the electrical circuit. This work proposes to take advantage of recent developments on thin-film solar cells and insert a photovoltaic (pv) tether segment in between the anodic and the cathodic contacts. Since thin-film solar cells can be folded and manufactured with any desired length and the same cross-section dimensions as the bare segment, i.e. width and thickness around few centimeters and tens of microns, the resulting device is compact and preserves bare tether simplicity. Detailed analysis of the current and voltage profiles throughout the tether shows that the electrical power introduced by the pv-segment into the tether-plasma circuit improves the performance and makes them less dependent on ambient conditions. The pv-segment decreases considerably the tether-to-plasma bias at the cathodic contact, thus opening the possibility to emit substantial current while using consumable-less electron emitters like thermionic and electron field emitters. The pv-segment also favors the current collection by increasing the tether-to-plasma bias at the bare segment. Propulsion and power generation applications and alternative architectures of bare-pv tethers are briefly discussed. This work received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 828902 (E.T.PACK project). GSA work is supported by the Ministerio de Ciencia, Innovación y Universidades of Spain under the Grant RYC-2014-15357.

The results of experimental studies on the generation of x-rays when operating a piezoelectric kitchen lighter in a vacuum are presented. For the first time, a new method for increasing the intensity of x-ray radiation in the piezoelectric effect in a high vacuum through the use of an additional electron emitter is proposed and demonstrated. The maximum energy of x-ray bremsstrahlung reaches 14 keV. This means that electrons are accelerated in vacuum in the field of a piezoelectric ceramic to energy of at least 14 keV.

A sheet beam electron gun with high compression ratio and long transmission distance performance for $W$ -band traveling-wave tube (TWT) is presented. A beam focusing electrode (BFE) with two pairs of unequal length outstretched structures is designed to provide equal positions of beam waist in both horizontal and vertical planes, which is beneficial to obtain large compression ratio and keep the beam cross section shape over a long distance. The operational voltage is set as 30 kV. The beam current is 0.505 A, and the corresponding cathode current density is about 5.59 A/cm2. The simulation results show that the electron gun can provide a stable sheet beam under a 0.85-T magnet field. The compression ratio of the obtained sheet beam can be over 35, and the sheet beam can be transported through a 126-mm beam tunnel without interception with a 0.6 fill factor. The parameter sensitivities of the gun are analyzed and discussed as well.

In this article, the design and experimental verification of a 200-kW ${Q}$ -band gyrotron traveling wave tube (gyro-TWT) amplifier are presented. A low-velocity spread magnetic injection electron gun (MIG), a new type of multichannel TE01 mode input coupler, and a broadband double-disk output window are adopted in the design to improve the performance of the gyro-TWT. At the same time, the lossy ceramic ring-loaded high-frequency interaction circuit is constructed to provide the required loss for stable operation, and the potential oscillations are effectively suppressed. Saturated peak power of 208 kW and 12.5-kW average output power are measured at 47 GHz by hot test, corresponding to a saturated gain of 50.2 dB, an efficiency of 29.4%, and a −3-dB bandwidth of 5.5 GHz.

This article presents the results of a design study of an electron-optic system (EOS) for a sheet-beam ${G}$ -band traveling-wave tube. An electron gun providing a 0.1-A, 20-kV sheet beam emitted by a 0.8 mm $\times0.8$ mm curved cylindrical cathode is designed. The beam dimensions at waist position are 0.05 mm $\times0.8$ mm with a compression ratio of 16 in the vertical direction. A magnetic system providing 1.1 T magnetic field, which is nearly seven times higher than the Brillouin field, is designed, and beam transmission in the 0.1 mm $\times0.85$ mm beam tunnel is studied by 3-D particle-in-cell (PIC) simulation. It is demonstrated that the beam has a complex structure of particle distribution, i.e., a high-density central part (core) and a peripheral low-density part (halo). The effect of assembly tolerance on beam transmission is studied. The prototype gun is fabricated, which compresses the beam to 0.1 mm by electrostatic field only. The 135-mA current with 95% transmission through the 0.2-mm anode aperture is measured.

A field electron emitter is a promising cold electron source that can be applied in various vacuum micro/nanoelectronic apparatus. On the other hand, triboelectric nanogenerators (TENGs) harvest me...

With the potential to be an excellent field electron emitter, few-layer graphene (FLG) has to avoid Joule heat induced vacuum breakdown during high current field electron emission. Creating a good heat dissipation path is the key factor maintaining the heat equilibrium of a field emitter. In this work, a graphite interlayer was grown between the FLG and the tungsten substrate. The graphite interlayer with its good in plane electrical and thermal conductivities helps FLG dissipate the heat in the lateral direction efficiently and broaden the heat dissipation path. As a result, both the temperature of the FLG and the chance of vacuum breakdown were reduced. The destructive in situ TEM field emission test of a single FLG showed that the breakage of the graphite interlayer during field emission blocks up the lateral heat dissipation path, causes heat accumulation and finally induces the vacuum breakdown of FLG. Benefiting from the graphite interlayer, the high current field emission characteristics of a single FLG were achieved. The maximum field emission current of six single FLG samples was between 78 and 233 μA with the corresponding current densities in the range of 1.2 × 107-5.85 × 108 A cm-2. This finding demonstrates that interface heat engineering is crucial for nanomaterial-based field emitters that work under high current and high temperature conditions.

Results are presented from a theoretical study on optimizing the parameters of an electron gun of a powerful multicavity extended interaction klystron at a frequency of 95 GHz, ensuring the formation of a dense annular electron beam and its transport through interaction region with a current transmission coefficient of 99%, with taking into account of the thermal spread of electron velocities at the cathode.

In this article, the design approach for a ${V}$ -band miniaturized oscillator with a pseudospark-based high-current-density sheet electron beam source is presented. The hollow cathode electron gun has been designed and developed. In the experiment, the ~10-A current in the hollow-cathode phase has been measured. The high-frequency structure comprised of a truncated sine waveguide slow wave structure (TSW SWS) with wideband-matched output couplers has been designed, optimized, and simulated. The simulations show good transmission characteristics of the structure. The operation of a backward-wave oscillator with the designed TSW SWS driven by a 10-A, 40-kV sheet electron beam has been investigated by using 3-D particle-in-cell simulations. The maximal output power of 70 kW has been attained in the simulation. Frequency tuning within the 10-GHz frequency band has been demonstrated.

The perveance, ${K}$ , one of the Pierce electron gun (PEG) outputs, is completely dependent on geometric features, including the anode–cathode spherical distance, ${D}_{\text {ac}}$ . If the measured ${K}$ is not desirable after assembling, or the center of the cathode is not aligned with the anode axis, the PEG should be disassembled. In this article, with respect to the effects of spherical aberration and thermal velocity, a PEG is designed, simulated by computer simulation technologies (CSTs)-particle studio (PS) software, and manufactured for an ${S}$ -band klystron with ${K} = 1.5\,\,\mu $ and variable ${D}_{\text {ac}}$ . A new part in the PEG is designed that is called the spring film. It can move the cathode ±1 mm in the ${z}$ -direction while the other components are fixed and the vacuum of PEG does not change. The initial design leads to ${D}_{\text {ac }}$ to be 3.6 mm, but since ${K}$ is not expected as what we were looking for, so the desired ${K}$ is obtained by changing ${D}_{\text {ac}}$ , also the other parameters changing with ${D}_{\text {ac}}$ are examined and their values are estimated from the simulation. Finally, it is concluded that with the newly designed electron gun, unlike conventional PEGs, some parameters like perveance, cathode current, cathode lifetime, and body current are not fixed and they can be changed or improved.

High Power S-band pulsed klystrons with peak power greater than 6 MW are widely used as RF sources in particle accelerators. This paper presents an electron gun (pierce type) design for such a klystron with an output power of 8 MW peak and 30 kW average with its intended applications in accelerators for food processing. The targeted device is currently under design at CSIR-CEERI and will be developed later on. The results of electron gun simulation through computational codes like Trak, CST particle studio, and Opera are compared to find an optimum design for the electron gun to be fabricated for the klystron.

Proceeding of: Sixth International Conference on Tethers in Space, Madrid, June 12-14, 2019 The Electrodynamic Tether Technology for Passive Consumable-less Deorbit Kit (E.T.PACK) is a project aimed at the development of a deorbit kit based on low-work-function Tether (LWT) technology, i.e., a fully passive and electrically floating system made of a long conductive tape coated with a low-work-function material. The LWT interacts passively with the environment (ambient plasma, magnetic field, and solar radiation) to exchange momentum with the planet's magnetosphere, thus enabling the spacecraft to de-orbit and/or re-boost without the need for consumables. The main goal is to develop a deorbit kit and related software with Technology Readiness Level 4 and promote a follow-up project to carry out an in-orbit experiment. The planned kit in the experiment has three modes of operation: fully passive LWT and conventional electrodynamic tether equipped with an active electron emitter in passive and active modes. Several activities of the project pivot around the C12A7 : e- electride, which will be used in four hardware elements: (i) LWT (ii) hollow cathode, (iii) photo-enhanced thermionic emission device to convert solar photon energy into electrical energy, and (iv) a hollow cathode thruster. These elements, some of which do not belong to the deorbit kit, are synergetic with the main stream of the project and common to some tether applications like in-orbit propulsion and energy generation. This work explains the activities of E.T.PACK and the approach for solving its technological challenges. After reviewing past progresses on electrodynamic tethers and thermionic materials, we present a preliminary concept of the kit for the in-orbit experiment, some simulation results, and the key hardware elements. This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 828902 (E.T.PACK project). GSA work is supported by the Ministerio de Ciencia, Innovaci on y Universidades of Spain under the Grant RYC-2014-15357. SN work is supported by Comunidad de Madrid (Spain) under the Grant 2018/T2IND/11352

Bu çalışmada, elektron spektrometresi kullanılarak, Helyum (He) atomunun rezonans düzeylerinin açısal değişimleri ölçülmüştür. 200 eV enerjili elektron demeti, yüksek vakum ortamında He atomları ile çarpıştırılarak koparılan ve saçılan elektronlar dedekte edilmiştir. Elektron spektrometresi deney düzeneği; vakum sistemi, elektron tabancası, hedef gaz He, saçılan ve koparılan elektronları dedekte eden iki elektron enerji analizörü, elektron dedektörleri, sinyal işleme ünitesi ve Faraday Elektron Toplayıcıdan (FET) oluşmaktadır. Bu çalışmada, soygaz element serisinde olan Helyum atomunun kendiliğinden iyonlaşma enerji seviyeleri 10o-80o açı aralığında incelenmiştir. Enerji değerleri 32,5-35 eV olarak alınmıştır. Küçük açılarda rezonans profillerinin simetri durumlarının daha baskın olduğu görülürken, büyük açılara doğru kayıldıkça hem simetrik hem asimetrik yapıda oldukları görülmüştür., In this work, the angular variations of the He atom for the resonance levels were experimentally measured by electron spectrometer. 200 eV energetic electron beam collided with Helium (He) gas in high vacuum and scattered electrons were detected. Measurements were taken for angular variation for fixed incident electron energy. The experimental setup in the electron collision laboratory consists of an electron gun, as target He atom, two electron energy analyzers, electron detectors, signal processing units and Faraday Electron Cup (FEC). Here, the auto ionization energy levels of the He atom (in the rare gas element series) for 10o-800 angular range were examined. Differential cross section measurements (DCS) of resonance energy levels were inspected for 32,5-35 eV. Although the symmetry states of resonance profiles are more dominant in the small angle range, both symmetrical and asymmetrical structures are observed for larger angles.

The use of titanium-sapphire-laser radiation with a low pulse repetition rate made it possible to operate a metal tip (without its destruction) as an electron emitter at an increased intensity of laser radiation on the tip. As a result, an emission of electrons with a charge in the range of tens of picocoulombs per laser pulse was obtained from a metal tip with a characteristic radius of a curvature of ~1 μm.

The key subsystems of a high efficiency material processing gyrotron are designed at an operating frequency of 27.885 GHz. A triode-type electron gun is designed to launch hollow spiraling electron beam. The outer diameter of the gun is kept at 50 mm to lower inside diameter of the magnet. Start oscillation current for TE02 operating as well as competing modes is plotted. The output power and efficiency are predicted to be 18.4 kW and 46%, respectively, based on single mode time-dependent analytical equation. Beam–wave interaction is studied by employing particle-in-cell (PIC) simulation. Electronic efficiency and output power are increased by operating the tube in hard excitation region. An axially slotted cavity is adopted to abridge mode competitions. The output power and electronic efficiency are obtained to be 20.08 kW and 50.2%, respectively, without considering any velocity spread of the electron beam. However, the efficiency is reduced to 45%, when a moderate transverse velocity spread of 5% is considered. The power efficiency is enhanced to 67.07% by introducing a 3-staged depressed collector.

The High Energy Photon Source (HEPS) is a synchrotron radiation source with an ultrahigh brightness and under construction in China. Its accelerator system is comprised of a 6-GeV storage ring, a full energy booster, a 500-meV Linac and three transport lines. With deepening investigations on the physics designs of the storage ring and the booster, the physics scheme of the Linac has evolved through multiple versions. The final version of the Linac, including the electron gun, bunching system and main accelerator, has been determined. The Linac is an s-band normal conducting electron linear accelerator with a very high bunch charge and a large bunch charge range. Based on simulations, the Linac could provide electron bunches with charge greater than 8.5-nC, meeting the energy spread and emittance requirements. This paper first reviews the evolution and main considerations for different design versions and then describes the physics design and dynamic simulation results of the final scheme in detail.

A pumped vacuum apparatus is described that contains an electron gun with an adjustable high-voltage voltage source, interchangeable metal targets, and flanges to which the object under study is connected. The apparatus is especially designed to measure the spatial and temporal characteristics of high-speed image converter streak cameras that operate in the soft X-ray range. It can be used for research and measurements in the design of soft X-ray photodetectors and their main parts, for example, microprobe detectors, imaging devices, solid-state linear and matrix photodetectors, photoemitters operating in vacuum, etc.

Gas-filled neutron tubes generating pulses with specified parameters are needed for neutron well-logging. These parameters are affected most by the ion-pulse shape. The results of numerical modeling of the dynamics of the electron beam, secondary ions, and electrons generated in the volume of the Penning ion source with an electron emitter and their effect on the ion-pulse parameters are examined. The calculation was performed in an axisymmetric geometry with the aid of the KARAT software package. The physical processes occurring in the ion source and their influence on the growth of the ion current extracted from the plasma as a function of the maximum current of the injected electrons and the geometry of their source were analyzed. It was found that the steady-state ion current is independent of the electron current and is mostly due to the geometry and radius of the electron beam.

The Ka -band extended interaction klystrons (EIK) have been developed at the Institute of Electronics, Chinese Academy of Sciences (IECAS), to satisfy the requirement for the high-power millimeter-wave sources in scientific researches. In this work, two kinds of high compression electron gun with the solid or hollow beams, the derivative electron optics systems using the compact permanent magnet uniform focusing and the shared efficient interaction circuit based on the multigap ladder cavity, have been studied in detail and well designed through a mass of calculations. After the mechanical design, finely manufacturing, and a series of technical processes, the Ka -band EIK prototype tubes have been successfully built and tested. For the solid beam scheme, the maximum output power achieves 20 kW in the bandwidth of 60 MHz, and, correspondingly, the gain of 53 dB and the efficiency of 24% are observed. The measured −1 and −3 dB bandwidths are about 220 and 350 MHz, respectively. Meanwhile, the beam transmission is excellent, that is over 97% in dc state and over 90% in RF operation. For the hollow beam case, an over 91% dc transmission test has finished.

In this article, a novel approach for optimizing a practical 270° bent electron gun has been proposed by using JUPYTER NOTEBOOK, an open-source web application utilizing PYTHON script, aiding faster data processing and mathematical computations. For this purpose, a 3-D cost function has been formulated to optimize the position of the anode with respect to the filament which aims at maximizing the beam power density, maximizing beam parallelism or laminar flow and optimizing beam shape. CST Studio-Particle Tracking Module is used for gun design, magnetic field design, and for the study and analysis of generated electron beam trajectories by performing both electrostatic and electromagnetic 3-D gun simulations. Unlike the conventional 270° bent transverse electron guns using Helmholtz coils for generating uniform magnetic fields, here permanent magnets have been used for generating nonuniform magnetic fields making the overall system compact along with electromagnets and magnetic shunts for precise beam maneuvering. Magnetic fields are experimentally measured by using Gauss meter which match well with that of the simulated values. The electron gun was fabricated and trial experiments were conducted under high vacuum environment. Experimental validation was done by puncturing a stainless steel plate kept at 90° and 270° positions above the crucible and the results match well with the simulated results.

A new scheme of the cathode assembly of a high-current electron gun is presented. The initiation of explosive emission is carried out using of 69 parallel triggered spark gaps, the electrodes and tubular ceramic insulators of which are built into the disk explosive-emission cathode. The efficiency of the proposed scheme and the high emissivity of the cathode assembly, which is approximately 1.5–1.7 times higher than the emissivity that is characteristic for a traditional gun scheme with a plasma anode and a copper-braided explosive emission cathode, are demonstrated.

A multitube configuration for a gyrotron traveling-wave amplifier (gyro-TWA) that is based on the use of one multibeam electron gun and several parallel helically corrugated interaction waveguides operating with axis-encircling-like electron beamlets at the second cyclotron harmonic is proposed. This new gyro-TWA concept, similar to that for multibeam or clustered linear-beam klystrons, can provide a multifold decrease in the thermal loading and increase in the RF breakdown strength for each tube at the same average or pulse output powers or a significant increase in the output power at a moderate level of the mentioned factors. It is shown that the multibeam electron flow appropriate for such a multitube gyro-TWA can be formed by a single magnetron-injection gun (MIG) using selectively emitting regions on the cathode. In some cases, such a gun can be less sensitive to the influence of space-charge forces and other disturbing factors and generate a beam of better quality than a single-beam cusp gun. In particular, a gun for the ten-tube ${W}$ -band gyro-TWA, which ensures generation of a beam with a total power of about 1.3 MW, a pitch factor from 1.2 to 1.5, and a root-mean-square (rms) transverse velocity spread of about 8%, was designed and numerically modeled.

We have demonstrated and developed a W-band 30 W continuous-wave folded waveguide traveling wave tube (CW FWTWT) with 13.5-kV operation voltage and 4.8 dB gain flatness. In this paper, we quantitatively study the relationship between operating voltage and the key geometric dimensions of a folded waveguide, which is the key to the design of the low-voltage TWT. In addition, problems of improving beam transmission and suppressing oscillations are also studied, and the related design methodologies of the long-range electron gun, periodic permanent magnet (PPM) focusing system, low-voltage standing wave ratio (VSWR) coupling system, and horseshoe attenuator are discussed. On the basis of the above analysis, we have designed and fabricated two types of W-band CW TWTs. The test results show that beam transmissions are over 98.5% at DC and better than 96.5% at the highest peak RF power. Measured saturated output powers are greater than 33.6 W with saturated gain more than 42.2 dB within frequency range of 91–99 GHz, and an improved gain flatness of 4.8 dB is achieved.

In this work, we have discussed a novel electron gun beam method used for the preparation of an Osmium foil sample at Daresbury Target Preparatory Laboratory, UK, which was used during the 192Os(18O, 16O)194Os 2 neutron transfer reaction at IFIN-HH Bucharest. The successful measurement of gamma energies associated with the 194Os isotopic nucleus recorded from the experiment with the high resolution HPGe detectors from this clean target of 192Os showed that this method has proven very efficient in preparing the most difficult osmium target which other methods like the sputtering, thermal evaporation could not get it prepared due to the high melting point of about 3000 0C found in the Osmium foil.

The VEPP-5 injection complex, consisting of two linacs and a damping storage ring, delivers electron and positron beams to the VEPP-4M and VEPP-2000 colliders operating at BINP. Over three years of injector operation, its efficiency has significantly increased and the maximum positron-storage rate has reached 1.2 × 1010 s–1. This progress was reached through tuning the constituent machines, upgrading the accelerator technology, and deploying a new 11-MHz station of RF cavities. By the start of the next running season, a new electron gun with a significantly increased maximum current and cathode lifetime will be installed.

This article presents a design of the triode coaxial magnetron injection gun (CMIG) for a 170-GHz MW-class gyrotron. The trade-off equations have been used to initialize the design of gun geometry and beam parameters. The operating mode of gyrotron is TE34,11 at fundamental harmonic. The 3-D electron tracing code CST Particle Studio has been employed to simulate and optimize the CMIG design. An optimum electron beam with transverse to longitudinal velocity ratio $\alpha = 1.3 $ and transverse velocity spread $\delta \beta _{\bot }= 3.29\%$ has been obtained. The sensitivity analysis of electron gun parameters are also investigated including geometric deviations and misalignments.

The design of a magnetron-injection gun (MIG) suitable for using in the CW 3-rd harmonic gyrotron with an output frequency of 1.185 THz and an output power about 100 W, intended for DNP/NMR spectroscopy applications is described. To improve the mode selection, several electron optics schemes are investigated. The MIG allows using both single-beam and double-beam schemes of the gyrotron operation with two different operating modes. Requirements for the electron beam parameters were found. The design of the triode MIG forming two generating beams with a quality suitable for 3-rd harmonic operation is suggested and optimized. The specific feature of the MIG is the possibility to form either two beams or one beam using the same electrode geometry and different number of emitting rings. The suggested MIG is not sensitive to small misalignment and reasonable manufacturing errors. A key feature of the design is that to improve the mode selection an electron beam with increased velocity spread is proposed. It is shown that it is possible to form two beams with practically equal and quite high pitch factors in all range of operating currents and at the same time small enough coefficient of reflection from the magnetic mirror in spite of large enough value of velocity spread.

The paper presents the results of a study of a glow spatial structure and temporal dynamics of a hybrid discharge combining a high-current reflective discharge with vacuum arcs at a voltage supplying the discharge up to 9 kV and working gas (argon) pressures of 0.1–1 mTorr. The possibility of forming a plasma anode with enhanced ion density at the periphery has been demonstrated with the use of this discharge. Preliminary results of measurements of the energy density distribution over the cross section of a low-energy (up to 30 keV) high-current (up to 25 kA) electron beam formed in an electron gun with explosive emission cathode and plasma anode based on the hybrid discharge are also presented. The promise of the proposed method for improving the beam homogeneity has been shown.

The studies of thermal-dependent properties, including the high-efficiency heater, thermal deformation of the cathode and focusing electrode (FE), and the associated beamforming problems of a sheet beam gun (SBG) for a ${W}$ -band sheet beam extended interaction oscillator (W-SBEIO), are presented. A simple but efficient method is proposed to complete the 3-D thermal simulations of SBG, including the contact thermal resistance. The heater efficiency is greatly improved by a three-layer folded cathode supporter. Almost 50% reduction in heating power (31.6–15.9W) is achieved at 1100 °C cathode temperature. The corresponding test was conducted on the optimized structure, and the experiment results validated its effectiveness. Besides, the axial thermal expansion is decreased by 38.9% and 47% for the cathode and the FE separately. The sheet beamforming deterioration caused by thermal deformation is studied by 3-D simulations. The prepositioning of cathode and bias potential of FE is applied to keep ideal beamforming with a 45-kV 2-A and 6.8 mm $\times0.36$ mm sheet beam.

Spatial structure of glow and time dynamics of a hybrid discharge that combines high-current reflective discharge and vacuum arcs induced by spark breakdown on dielectric surface are studied at a supply voltage of up to 9 kV and working gas (argon) pressures of 0.1–1 mTorr. A plasma anode with an increased peripheral concentration of ions can be formed, in particular, with the aid of an auxiliary shield. Distributions of energy density are measured over the cross section of a nonrelativistic (up to 30 keV) high-current (up to 25 kA) beam generated in an electron gun with an explosive emission cathode and a plasma anode based on this (hybrid) discharge. The results are comparable with the results obtained using concentrators of magnetic field. It is expedient to employ the proposed method for improvement of uniformity of the beam, since application of the concentrators may be impossible.

In this article, the design and simulation of an electron injector based on a thermionic RF-modulated electron gun for particle accelerator applications is presented. The electron gun is based on a gridded thermionic cathode with the geometry based on a Pierce-type configuration. Both theory and numerical simulation were used to explore the relationship between the bunch length and the charge. The reasons for the pulse widening were also analyzed. The beam dynamics simulations showed that a minimum pulselength of 106 ps could be achieved with a bunch charge of 33 pC when the driving RF frequency was 1.5 GHz. The average transverse emittance was about 17 mm·mrad from the particle-in-cell simulations. Operating at a higher RF frequency did not significantly reduce the micro pulselength.

The short wavelength of far ultraviolet C (UVC) light sources is effective for various applications that include sterilizing bacteria and viruses, water purification, and sensing. Here, a triode structure UVC light source tube operating at ∼270 nm using a carbon nanotube (CNT) electron emitter as an excitation source is achieved to overcome the known issues with a conventional UVC-LED. The cathodoluminescence (CL) layer-based AlGaN MQW heterostructure is evaluated for UVC light emission. For comparison, the AlGaN-based MQW heterostructure was grown on a conventional sapphire substrate (CSS) and a nanopatterned sapphire substrate (NPSS). The NPSS efficiently enhanced the emission efficiency of UVC light, compared to that grown on a CSS. The output power of the UVC light source tube with AlGaN MQWs grown on NPSS was 2.33 times higher than that grown on CSS. Correspondingly, a high-power efficiency of 1.87% was demonstrated through a 2 inch light-emitting area with a low consumption energy of 18 W (anode voltage 9 kV; anode current 2 mA).