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Dissociative electron attachment (DEA) of a molecular target XY, e− + XY → XY− → X + Y−, is an important process in plasma, atmosphere, interstellar space, and ionizing radiation. DEA dynamics, i.e., the formation and fragmentation of an electron–molecule resonant complex, can be unveiled by measuring the product Y− with the velocity map imaging (VMI) technique. However, it is still challenging to achieve a high-resolution VMI measurement. Recently, we developed a high-resolution DEA apparatus that combined the VMI technique with a trochoidal electron monochromator. The energy spread (around 500 meV) of thermally emitted incident electrons can be reduced remarkably, but the monochromatized electrons become diffuse again in energy when being pulsed with an electric pulse applied on the grid electrode because the electron beam must be pulsed in the VMI measurement. Now this long-standing technical contradiction is settled by introducing a parallel resistance-capacitor circuit to the electrode of an electron gun. A delay-line detector is used for the VMI measurement, which allows the three-dimensional velocity or momentum images of multiple anionic yields to be recorded efficiently. Our high-resolution VMI apparatus works at a pulse frequency of 5 kHz and an energy spread of about 120–150 meV, and its credible performances are exhibited by the measurements of the DEA processes of CO(a3Π) and NO2. [ABSTRACT FROM AUTHOR]

In this work, we have made experimental measurements of multiple-hump total electron emission yield (TEEY) curves on SiO2 thin films. A Monte-Carlo electron transport model, published in Gibaru et al., J. Electron Spectrosc. Relat. Phenom. 261, 147265 (2022), has been developed to analyze the physical reasons of such atypical behavior. It is shown that the multiple-hump TEEY curves of thin dielectric layers are due to internal recombination effects. However, such kind of phenomenon is demonstrated to be strongly correlated to the incident current density. This analysis reveals that the double-hump TEEY curves observed commonly on insulators are also most probably a measurement artifact, tied to the operating parameters of the electron gun. A careful choice of experimental parameters can eliminate this artifact, by using a constant current density that is also low enough to limit recombination effects. [ABSTRACT FROM AUTHOR]

The accelerating electrode of a four-dimensional transmission electron microscope electron gun is modeled. The general expression of the electric-field distribution is derived for any point on the axis in a cylindrical coordinate system, and equations for the shape parameters of the electrode plate are obtained. The accuracy of the field expression is determined for different electrode plate parameters, and the shape parameters of the electron gun electrode are further investigated. This work can provide a theoretical basis for the initial design of a transmission electron microscope electron gun and the retrofit design of a four-dimensional electron gun. [ABSTRACT FROM AUTHOR]

The carbon nanotube cold cathode has important applications in the X-ray source, microwave tube, neutralizer, etc. In this study, the characteristics of carbon nanotube (CNT) electron gun in series with metal-oxide-semiconductor field-effect transistor (MOSFET) were studied. CNTs were prepared on a stainless steel substrate by chemical vapor deposition and assembled with a mesh gate to form an electron gun. The anode current of the electron gun can be accurately regulated by precisely controlling the MOSFET gate voltage in the subthreshold region from 1 to 40 µA. The current stability measurements show the cathode current fluctuation was 0.87% under 10 h continuous operation, and the corresponding anode current fluctuation was 2.3%. The result has demonstrated that the MOSFET can be applied for the precise control of the CNT electron gun and greatly improve current stability. [ABSTRACT FROM AUTHOR]

Temperature control is important in second harmonic generation (SHG) based on non-critical phase matching, which is widely used in the accelerator field to generate drive lasers. To further improve the stability of the drive laser for the DC-SRF photocathode electron gun at Peking University, a high-precision temperature control oven for lithium borate (LBO) crystals was developed. The oven's structure was designed to minimize heat exchange with the external environment. The temperature control circuit uses a thermoelectric cooler to ensure the temperature stability of the sampling circuit. The program utilizes a cascaded proportional-integral-derivative and an anti-saturation integral algorithm to achieve high-precision temperature control. Experiments showed that fluctuation at the working temperature of the LBO crystal in this oven was within ± 0.009 °C, corresponding to a root mean square (RMS) jitter of 0.003 °C, and the long-term power fluctuation of the 13.7 W green laser generated with SHG was less than 1%. [ABSTRACT FROM AUTHOR]

The design and development of the electron gun for vacuum electronic devices is a critical and challenging task having a profound impact on device performance. Current state-of-the-art electron gun simulation codes employ the concept of a virtual cathode for the simulation of space charge-limited electron guns, where the virtual cathode distance is to be provided as an input by the user. In this report, an approach to calculate the virtual cathode position through analytical formulation and simulation is presented. The effect of inaccurate virtual cathode on gun parameters is studied through simulation and its repercussions are explained. The approach has been applied in the simulation using three-dimensional tracking solver to design a 50 kV, 10 Amp electron gun, which is to be used in a C-band Klystron. Based on the design, a Gun-Collector-Test-Module (GCTM) has been developed and hot-tested for experimental validation. A good agreement between the simulated and measurement results validates the design approach of the electron gun. [ABSTRACT FROM AUTHOR]

The design, simulation, and beam dynamics analysis of the integrated illumination system of the scanning electron microscope (SEM) have been reported. The dimensions and capacity of the SEM components, such as the electron gun, electron column, and lenses, were determined using the finite element method. The optimization of the illumination system was performed, and characteristics beam parameters were studied analytically. The gun consisted of a simple diode structure having; cathode, Wehnelt, and anode electrodes. A tungsten cathode of diameter 150 μm was used to emit the electrons thermionically. The electrons beam was generated at 2700 K with acceleration potential of 15 kV. Pair of electromagnetic lenses producing field strengths, 221 mT and 253 mT, respectively, focused the beam at 56.5 mm from cathode, with beam diameter of 9 μm in the post anode region. The calculated value of beam brightness was 2.97 × 106 A/(mm-rad)2. The final beam spot thus obtained was stable and perfectly symmetric along the two transverse directions. Gun assembly and lenses are thermally stable at the operational temperature. The illumination system geometry offers full-beam collimation control with reduced column length, making it suitable for electron diffraction studies, where focusing of the beam onto a sample is desired. [ABSTRACT FROM AUTHOR]

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We investigated electron emission characteristics of a hafnium carbide [HfC(100)] single-crystal tip at various temperatures toward finding a candidate of the next generation of emitters for electron microscopes. The emission mode changed from cold-field emission (CFE) to low-temperature and high-temperature thermal-field emission and, finally, to extended Schottky emission. The energy width at full width of half maximum of the emitted electrons was 0.2 eV in the CFE mode at an angular current of 20 μA/sr, and it showed good emission stability with current noise less than 3.5% in an electron gun of a scanning electron microscope (SEM). Spatial resolution of the SEM at an acceleration voltage of 0.5 kV improved 14% by using the HfC(100)-CFE tip instead of a conventional W(310)-CFE tip. High monochromaticity and stable electron emission of the HfC(100)-CFE tip are suitable for the next generation of emitters for ultrahigh-resolution field emission SEMs. [ABSTRACT FROM AUTHOR]

The polarized electron source is a critical component in accelerator facilities such as the electron–ion collider, which requires a polarized electron gun with higher voltage and higher bunch charge than existing sources. One challenge we faced was the surface charge limit of the distributed Bragg reflector GaAs/GaAsP superlattice (DBR-SL-GaAs) photocathode. We suppressed this effect by optimizing the surface doping and heat cleaning procedures. We achieved up to 11.6 nC bunch charge of polarized electron beam. In this report, we discuss the performance of tests of a DBR-SL-GaAs photocathode in the high voltage direct current gun. Possible reasons for the observed peak quantum efficiency wavelength shift are analyzed, and we addressed it by using a wavelength tunable laser. In addition, the impact of the DBR layer and laser on the lifetime is investigated in this paper. The optimal DBR-SL-GaAs operating zone has been proposed, which gave us a long lifetime and high polarization at 30 μA operation. The success of this polarized gun will be key to the future of the nuclear sciences. [ABSTRACT FROM AUTHOR]

An electron gun that can produce MHz repetition rates and nanosecond pulses is described. The gun uses a Pierce grid in combination with an anode to extract electrons from a tungsten filament cathode. The electrons emerging from the anode are accelerated and focused using two triple-aperture lenses to form a beam. By applying a high slew rate grid pulse that transitions through the extraction voltage region of the grid/anode combination, pulses of electrons are produced from the gun that have temporal widths less than 5 ns. The pulsed beams are produced at both the rising and falling edges of the driving pulse. The characteristics of the emerging electron beams have been determined using an (e, 2e) coincidence spectrometer, and examples where they are used for time of flight decay measurements are presented. [ABSTRACT FROM AUTHOR]

Current day x-ray photoelectron spectroscopy (XPS) instrument makers have made significant advances in charge compensation systems over the last 20 years, which makes it easier to analyze insulators, but samples still have many differences in chemistry, dielectric properties, sizes, surface roughness, etc. that force instrument operators to tweak flood gun settings if they want or need to obtain high quality chemical state spectra that provide the most information. This guide teaches which flood gun variables to check, and how to optimize electron flood gun settings by presenting high energy resolution, chemical state spectra that show the result of using a poorly aligned flood gun on modern XPS instruments equipped with a monochromatic aluminum Kalpha x-ray source. This guide is focused on the XPS measurement of insulators—nonconductive metal oxides and polymers. This guide shows that by measuring commonly available polymers (polypropylene and polyethylene terephthalate) or ceramic materials (SiO2 and Al2O3), the operator can easily characterize the good and bad effects of XY position settings and other settings provided by modern electron flood gun systems. This guide includes many original, never-before-published XPS peak full width at half maximum (FWHM) that will greatly assist peak-fitting efforts. This guide reveals a direct correlation between electron count-rate and best charge-control settings. This guide discusses sample and instrument issues that affect surface charging and explains how to check the quality of charge control by measuring the FWHM and binding energy of C (1s) or O (1s) spectra produced from the sample currently being analyzed. A list of other charge-control methods is provided, along with advice and a best-known method. The availability of large extensive databases of actual spectra is extremely beneficial to users who need real-world examples of high quality chemical state spectra to guide their in-house efforts to collect high quality spectra and to interpret valuable information from the peak-fits of those spectra. [ABSTRACT FROM AUTHOR]

Low-emittance photoinjector-enabled cutting-edge scientific instruments, such as free-electron lasers, inverse Compton scattering light sources, and ultrafast electron diffraction, will greatly benefit from the improved repetition rate. In this paper, we proposed a specifically designed S-band radio frequency (RF) photoinjector to obtain low emittance and kilohertz (kHz) high-repetition rates simultaneously. By lowering the gradient, much lower RF power is needed to feed the electron gun, and then the heat problem is much easier to handle. Meanwhile, by optimizing the length of the gun's first cell from the normal case of 0.6-cell to 0.4-cell, the launch phase and the extraction field are significantly improved, thus ensuring the generation of low-emittance electron beams. In our design, the proposed 1.4-cell RF gun can work effectively under different field gradients ranging from 30 MV/m to 100 MV/m. For a standard case of 60 MV/m, 2.5 MW peak RF power with ys level pulse width is sufficient, thus offering the feasibility of improving the repetition rate to kHz level with a standard 5 MW irradiation klystron. In addition, simulated electron beams with a low emittance of 0.29 mm.mrad@200 pC can be generated by this proposed photoinjector, showing that this high-repetition rate injector holds the potential to deliver high-quality beams comparable to those of state-of-the-art S-band photoinjectors. Combining the merits of low emittance and high-repetition rate, this proposed photoinjector will provide a new possibility for future free-electron laser facilities operating at repetition rates ranging from kHz to tens of kHz. [ABSTRACT FROM AUTHOR]

The time evolution of beam properties in an electron bunch with the duration of a nanosecond was measured with a time resolution of several tens of picoseconds. A combination of horizontal and vertical slits cuts the beamlet from the original beam, with the current waveform of the beamlet measured using a fast wall-current monitor. The reconstruction of the waveform data obtained by scanning these two slits over the entire beam area provided the time evolution of the spatial profile. A similar measurement using two horizontal (vertical) slits separated by a certain distance also provides the time evolution of the phase–space profile. Using this method, the initial beam extracted from the CeB6 thermionic electron gun of the x-ray free-electron laser (XFEL) SACLA was evaluated. Although the slice emittance in the bunch was measured to be constant, the centroid of the spatial profile moved in the transverse direction by a few hundred micrometers in the 0.6 ns flat-top region. This movement arises from the temporal variation in the rectangular high-voltage pulse of the beam chopper and can cause an increase in the projected emittance. These measurements are important for evaluating the conditions of the initial beam emitted from the cathode and processed downstream of the gun. Hence, the proposed diagnostic system will play an important role in developing an extremely low-emittance electron beam or an artificial electron beam with a multi-bunch or micro-bunch structure that enhances the brightness of the XFEL light. [ABSTRACT FROM AUTHOR]

This paper presents the design and experiment results for a W-band sheet beam electron gun of the extended interaction oscillator (EIO). A 3D simulation has been performed, and then, the structure parameters of the electron gun have been optimized. The simulation results show that the beam waist (BW) and transmission ratio are extremely sensitive to the distance between the cathode and the focus electrode. By observing the beam waist and the beam range, the maximum beam range is up to 46 mm, which is measured at the beginning of the beam-wave interaction cavity. In addition, the thickness of the beam waist decreases rapidly when the cathode is moved along the positive axial direction by 0.03 mm. Moreover, the voltage on the focus electrode has a significant impact on the beam trajectory. At last, by considering the deviation, experiment results show that the transmission is improved to 98%. [ABSTRACT FROM AUTHOR]

A novel design methodology based on a current-tunable magnetic focusing system that can flexibly switch between Brillouin and immersive flow focusing modes is presented in this paper. Such a magnetic system, which comprises cascaded solenoid coils and pole pieces, could be used in beam optics systems of vacuum tubes, particle accelerators, and free-electron lasers. Although the profile of this magnetic system is not brand new, the novel way proposed in this paper to establish and manipulate such a system to fit versatile purposes has never been reported in the literature to the best of the authors' knowledge. The specific structure of the magnetic system should be optimized, starting from the immersive flow focusing mode together with the electron gun design, which will be determined on successful optimization. According to our analysis, such systems could be transformed into the Brillouin bunching mode by simply adjusting the coil currents without modifying the hardware. To verify such an approach, single-beam and multi-beam optical systems are demonstrated in this paper. Moreover, the beam radius in such systems could also be conveniently adjusted via a similar technique. [ABSTRACT FROM AUTHOR]

A superradiant FEL in the THz (3 THz) region is currently operating at Ariel University. It is based on the novel ORGAD accelerator, which is a hybrid linear RF photo-cathode 6 MeV electron gun. The hybrid term stands for its unique standing wave (SW)—traveling wave (TW) structure. The undulator generates spontaneous superradiance, which corresponds to spontaneous emission when the electron bunch duration is shorter than the radiated frequency, resulting in a much higher photon yield. However, the efficiency of this scheme is still quite low. In order to achieve higher emission (by improved efficiency), we intend to implement a new and promising radiative interaction scheme: tapering-enhanced superradiance (TES). This particular undulator design employs a tapered (amplitude) undulator in the zero-slippage condition to obtain a significantly more powerful and efficient THz radiation source. At the current stage, the scheme is designed for emission at approximately 0.5 THz. The design and start-to-end simulations demonstrate significant enhancement of superradiant energy and extraction efficiency using this method compared to a reference uniform case. [ABSTRACT FROM AUTHOR]

Current characteristics of a plasma-filled, high-current electron gun at different accelerating voltages and densities of plasma preliminary filling the space between the cathode and collector have been investigated. Multi-gap initiation of explosive emission is performed with the use of parallel operated, resistively decoupled arc plasma sources which electrodes and tube ceramic isolators are built-in to the explosive-emission cathode. Experiments have demonstrated operability of high-current electron gun with a new cathode assembly at accelerating voltage up to 30 kV and its good emissivity (average in area current density) which was approximately 1.4–2.4 times higher than an emissivity of traditional electron gun with plasma anode and multi-wire copper cathode. [ABSTRACT FROM AUTHOR]

This paper presents new structural data about mitochondria using correlative light and electron microscopy (CLEM) and cryo-electron tomography. These state-of-the-art structural biology methods allow studying biological objects at nanometer scales under natural conditions. Non-invasiveness of these methods makes them comparable to observing animals in their natural environment on a safari. The paper highlights two areas of research that can only be accomplished using these methods. The study visualized location of the Aβ42 amyloid aggregates in relation to mitochondria to test a hypothesis of development of mitochondrial dysfunction in Alzheimer's disease. The results showed that the Aβ42 aggregates do not interact with mitochondria, although some of them are closely located. Therefore, the study demonstrated that mitochondrial dysfunction is not directly associated with the effects of aggregates on mitochondrial structure. Other processes should be considered as sources of mitochondrial dysfunction. Second unique area presented in this work is high-resolution visualization of the mitochondrial membranes and proteins in them. Analysis of the cryo-ET data reveals toroidal holes in the lamellar structures of cardiac mitochondrial cristae, where ATP synthases are located. The study proposes a new mechanism for sorting and clustering protein complexes in the membrane based on topology. According to this suggestion, position of the OXPHOS system proteins in the membrane is determined by its curvature. High-resolution tomography expands and complements existing ideas about the structural and functional organization of mitochondria. This makes it possible to study the previously inaccessible structural interactions of proteins with each other and with membranes in vivo. [ABSTRACT FROM AUTHOR]

Background: Ultra‐high dose rate radiation (UHDR) is being explored by researchers in promise of advancing radiation therapy treatments. Purpose: This work presents the commissioning of Varian's Flash Extension for research (FLEX) conversion of a Clinac to deliver UHDR electrons. Methods: A Varian Clinac iX with the FLEX conversion was commissioned for non‐clinical research use with 16 MeV UHDR (16H) energy. This involved addition of new hardware, optimizing the electron gun voltages, radiofrequency (RF) power, and steering coils in order to maximize the accelerated electron beam current, sending the beam through custom scattering foils to produce the UHDR with 16H beam. Profiles and percent depth dose (PDD) measurements for 16H were obtained using radiochromic film in a custom vertical film holder and were compared to 16 MeV conventional electrons (16C). Dose rate and dose per pulse (DPP) were calculated from measured dose in film. Linearity and stability were assessed using an Advanced Markus ionization chamber. Results: Energies for 16H and 16C had similar beam quality based on PDD measurements. Measurements at the head of the machine (61.3 cm SSD) with jaws set to 10×10 cm2 showed the FWHM of the profile as 7.2 cm, with 3.4 Gy as the maximum DPP and instantaneous dose rate of 8.1E5 Gy/s. Measurements at 100 cm SSD with 10 cm standard cone showed the full width at half max (FWHM) of the profile as 10.5 cm, 1.08 Gy as the maximum DPP and instantaneous dose rate of 2.E5 Gy/s. Machine output with number of pulses was linear (R = 1) from 1 to 99 delivered pulses. Output stability was measured within ±1% within the same session and within ±2% for daily variations. Conclusions: The FLEX conversion of the Clinac is able to generate UHDR electron beams which are reproducible with beam properties similar to clinically used electrons at 16 MeV. Having a platform which can quickly transition between UHDR and conventional modes (<1 min) can be advantageous for future research applications. [ABSTRACT FROM AUTHOR]

The possibility of forming helical electron beams (HEBs) for multi-mirror and multi-barrel gyrotrons using systems with non-adiabatic injection of an electron beam into a magnetic field is analyzed. Systems where emission comes from circular arcs or from individual emission circles are considered. The possibility of implementing a HEB with a large (1.5–1.8) pitch factor, an acceptable velocity spread and a reduced influence of particles reflected from the magnetic mirror on the quality of the beam has been studied. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing technologies, such as electron beam powder bed fusion (PBF-EB), rely on layer heating to overcome the so-called "smoke" phenomenon. When scaled up for industrial manufacturing, PBF-EB becomes less productive due to the lengthy preheating process. Currently, only the electron beam (EB) is used for preheating in PBF-EB, resulting in increased manufacturing times, energy consumption, and in some cases limiting the applicability of the technology. In this study, a new preheating approach is suggested that incorporates a near-infrared radiation (NIR) emitter inside an PBF-EB system. The NIR unit eliminates the need for EB heating, reducing build time and powder charging. Successful builds using 316 L and Ti6Al4V precursor powders validate the feasibility of the proposed approach. The produced samples exhibit similar properties to those obtained by the standard PBF-EB process. The introduction of NIR technology also reduced build cost and increased the service intervals of the electron gun. [ABSTRACT FROM AUTHOR]

The article discusses the various methods of estimating the surface cathode temperature of the high-voltage glow discharge electron gun, which forms a ribbon electron beam with a linear focus. Numerical estimations have been made to design the cathode assembly of an industrial gun. It is shown that the most effective way to make approximate estimates of the temperature of the cathode surface in high-voltage glow discharge electron guns for various technological purposes is to use arithmetic-logical ratios for modeling the geometry of the cathode assembly and locus functions for estimating the temperature distribution. The accuracy of such estimates, made using the heat balance equation, was 5–10%, sufficient at the initial stage of designing an electron gun. It is shown that using the SolidWorks CAD software complex for designing high-voltage glow discharge electron guns is effective only for solving the complex engineering design tasks and preparing the corresponding technical documentation. The results of the theoretical research published in the article are of interest to a wide range of specialists engaged in developing electron beam equipment and its implementation in industrial production. [ABSTRACT FROM AUTHOR]

A comprehensive methodology for designing a magnetic deflection system for a technological electron gun is proposed. The feasibility of using deflection systems with an internal magnetic circuit and toroidal coil sections to form deflection fields that ensure azimuth beam rotation with a constant angle of deviation from the vertical axis is substantiated. The potential of computer modeling is shown both at the stage of calculating the deflection field and beam displacement and at the stage of creating the design of the system frame for its subsequent manufacture based on 3D printing. The main coil parameters are determined, and the circuit diagram of a current stabilizer with external control from a digital-to-analog converter is developed. Dependences are presented showing the relationship between control signals and deflection angles in the developed unit prototype. It is shown that the proposed technique is universal and can be used to create electron-optical gun elements providing deflection, scanning, parallel transfer or adjustment of technological electron beams. [ABSTRACT FROM AUTHOR]

Energetic characteristics of a high-current electron gun with a cathode assembly based on multi-gap initiation of explosive emission by dielectric surface flashover in the mode of vacuum and gas-filled diode were investigated. It has been shown that it is better to measure high-current electron beam pulse energy using a calorimetric (thermal imaging) method than to calculate it from the waveforms of accelerating voltage and beam current onto collector (target) since the beam current values may be essentially overstated because of decay current of a dense plasma emergent under the bombardment of a collector by the beam electrons. The best efficiency of the energy transfer from the capacitive storage of the high-voltage pulsed generator supplying an electron gun was observed in the case of gas-filled diode at a moderate pressure of the working gas (argon, 0.093 Pa). [ABSTRACT FROM AUTHOR]

The WCLL Breeding Blanket of DEMO and the Test Blanket Module (TBM) of ITER require accurate R&D activities, i.e., concept validation at a relevant scale and safety demonstrations. In view of this, the strategic objective of the Water Loop (WL) facility, belonging to the W-HYDRA experimental platform planned at C.R. Brasimone of ENEA, is twofold: to conduct R&D activities for the WCLL BB to validate design performances and to increase the technical maturity level for selection and validation phases, as well as to support the ITER WCLL Test Blanket System program. Basically, the Water Loop facility will have the capability to investigate the design features and performances of scaled-down or portions of breeding blanket components, as well as full-scale TBM mock-ups. It is a large-/medium-scale water coolant plant that will provide water coolant at high pressure and temperature. It is composed by single-phase primary (designed at 18.5 MPa and 350 °C) and secondary (designed at 2.5 MPa and 220 °C) systems thermally connected with a two-phase tertiary loop acting as an ultimate heat sink (designed at 6 bar and 80 °C). The primary loop has two main sources of power: an electrical heater up to about 1 MWe, installed in the cold side, downstream of the pump and upstream of the test section, and an electron beam gun acting as a heat flux generator. The WL has unique features and is designed as a multi-purpose facility capable of being coupled with the LIFUS5/Mod4 facility to study PbLi/water reaction at a large scale. This paper presents the status of the Water Loop facility, highlighting objectives, design features, and the analyses performed. [ABSTRACT FROM AUTHOR]

As the central component of the traveling wave tube (TWT), the thermal deformation of the electron gun is a critical concern. This paper presents a method for analyzing the electromagnetic characteristics of electron gun after thermal deformation. The method adopts multiple grid acceleration technology. Based on this method, a three-dimensional thermal stress analysis tool called the Thermal Stress Simulator (TSS) is developed. In addition, the TSS can be seamlessly coupled with the Thermal Simulator (TS) and the Electron Optical Simulator (EOS) previously developed by our team to realize the analysis of electromagnetic characteristics changes after thermal deformation and provide support for the reliable design of TWT. [ABSTRACT FROM AUTHOR]

The carbon nanotube cold cathode has important applications in the X-ray source, microwave tube, neutralizer, etc. In this study, the characteristics of carbon nanotube (CNT) electron gun in series with metal-oxide-semiconductor field-effect transistor (MOSFET) were studied. CNTs were prepared on a stainless steel substrate by chemical vapor deposition and assembled with a mesh gate to form an electron gun. The anode current of the electron gun can be accurately regulated by precisely controlling the MOSFET gate voltage in the subthreshold region from 1 to 40 µA. The current stability measurements show the cathode current fluctuation was 0.87% under 10 h continuous operation, and the corresponding anode current fluctuation was 2.3%. The result has demonstrated that the MOSFET can be applied for the precise control of the CNT electron gun and greatly improve current stability.

Field emission electron probe microanalyzers (EPMA) and scanning electron microscopes (SEM) have improved in both the hardware and software. They have become workhorse instruments for imaging secondary (SE) and backscattered (BSE) electrons. Recent advancements in technology provide qualitative quantitative analysis and X-ray maps at lower kVs and higher beam current without significantly enlarging the beam diameter. On EPMAs and SEMs with W and LaB6 electron guns, spatial resolution for microanalysis was ∼1 micron. Now, with field emission (FE) guns, resolution of 300 nm for quantitative analysis and mapping of elements well below 100 nm are possible. Software has also become more user-friendly and has advanced automation algorithms that allow the "non-expert" EPMA user to collect data. However, the best part of automation sits in the user's chair. The new EPMAs and SEMs can collect very good data, but if they don't answer the question that is being asked, they have no use. [ABSTRACT FROM AUTHOR]

In this work, a Spindt cold cathode electron gun with a PPM (periodic permanent magnet) focusing system for a terahertz TWT (traveling wave tube) was designed and simulated based on the Pierce electron gun structure. More specifically, a new 3D (three dimensional) emission model was used, where the cathode radius of the electron gun was 1 mm and the cathode current was 30 mA, with an emitting half angle of about 28°. It was demonstrated that the electron beam was well focused with an electron beam radius of 0.3 mm and a filling ratio of 0.5 when the maximum value of the PPM field along with the axis was 0.122T. According to the simulation results, a planar cold cathode electron gun was developed. Measurements demonstrated that the I/V characteristics of the cold cathode gun were consistent with that of a cold cathode, revealing that the electrons emitted from the cathode are not intercepted when passing through the electron gun. [ABSTRACT FROM AUTHOR]

In order to implement the electron beam melting technologies the E.O.Paton Electric Welding Institute of NASU developed a multifunctional electron beam unit UE-5810 of megawatt class, designed for producing ingots of titanium and its alloys of up to 20 tons weight. Description of a multipurpose universal electron beam unit UE-5810 and its specification are given. Functional features of the components of the unit, technological fixtures and electron guns are described. Electron beam unit UE-5810 is a reliable highly efficient installation of industrial type for melting highly reactive metals and alloys, as well as treatment of the produced ingots by glazing. [ABSTRACT FROM AUTHOR]

This study evaluates dosimetric data such as PDD, dose profile and tissue phantom rate (TPR20/10) after replacing the LINAC device's electron gun and ion chamber pump. These values obtained after the change were compared with the standard PDD protocol, British Journal of Radiology Supplement 25 (BJR 25) report, Beam Data (measured and recorded as reference values during the setup phase, BD) and simulation results. In additional, uncertainty results were obtained for absorbed doses to water using different calculation tools. The experimental setup was created in the GATE/Geant4 simulation program, and the experimentally obtained TPR20/10, beam profile and PDD values were compared with the simulation. The difference between TPR20/10 values for 6 and 18 MV photon energies was found to be below 1% for 6 MVs and 3% for 18 MV. When different calculation tools were used, uncertainties were found in the absorbed dose measurements ranging between 0.8% and 1.87%, which is compatible with the uncertainties (1.4-2.1%) specified in the IAEA report. Even though small uncertainties were observed in the results, the differences between the calculations in the measurements of absorbed doses were insignificant. Estimated uncertainties for GATE was a little smaller than those measured using experimental methods, BD and BJR 25. Although the values obtained are within the tolerance, after such significant materials are changed in the LINAC device, a water phantom should be set up, the measurements should be repeated, and the results should be confirmed to be within the limit values. [ABSTRACT FROM AUTHOR]

Novel photocathode materials like ordered surfaces of single crystal metals, epitaxially grown high quantum efficiency thin films, and topologically non-trivial materials with dirac cones show great promise for generating brighter electron beams for various accelerator and ultrafast electron scattering applications. Despite several materials being identified as brighter photocathodes, none of them have been tested in electron guns to extract electron beams due to technical and logistical challenges. In this paper, we present the design and commissioning of a cryocooled 200 kV DC electron gun that is capable of testing a wide variety of novel photocathode materials over a broad range of temperatures from 298 to 35 K for bright electron beam generation. This gun is designed to enable easy transfer of the photocathode to various standard ultra-high-vacuum surface diagnostics and preparation techniques, allowing a full characterization of the dependence of beam brightness on the photocathode material and surface properties. We demonstrate the development of such a high-voltage, high-gradient gun using materials and equipment that are easily available in any standard university lab, making the development of such 200 kV electron guns more accessible. [ABSTRACT FROM AUTHOR]

A test-Accelerator as Coherent Terahertz Source (t-ACTS) has been under development at Tohoku University, in which an intense coherent terahertz radiation is generated from the short electron bunches. Velocity bunching scheme in a traveling wave accelerating structure is employed to generate the short electron bunches. The in-phase and quadrature (IQ) modulator and demodulator were installed to the low-level RF systems of t-ACTS linac to control and measure the amplitude and phase of RF power. The amplitude and phase of the RF power applied to an RF electron gun cavities and the accelerating structure are controlled to produce the electron bunches with a uniform and small momentum spread suitable for the velocity bunching. By installing the feed-forward control system using IQ modulators for the beam conditioning, we have successfully generated flat RF pulses and improved beam quality, including the energy spectrum of the beam. The details of feed-forward control system of the amplitude and phase using the IQ modulator and the beam experiments are presented in this paper. [ABSTRACT FROM AUTHOR]

Nowadays, by expanding the application of thin layers in industry and medical sciences, their fabrication methods have also received attention. One of those methods is the vaporizing material method with the help of an electron gun. The most important part in the electron gun is the electron optic, which is responsible for producing and accelerating electrons, so that it becomes possible to vaporize refractory materials in a shorter period of time by better modifying and controlling the electron beam (the shape and diameter of the electron beam) at the target location. The reduction and control of the beam diameter in this evaporation source depends on various parameters such as device geometry, magnetic field intensity, electric power, etc. Therefore, in this research, the effect of those parameters was investigated by conducting experiments and using finite element and modeling software. The simulation results revealed that the effect of the effective parameters on the beam diameter can be predicted to a good extent, so that the diameter of the electron beam decreases by changing the geometrical shape, size and displacement of the output beam components. Then, the new electron gun, compared to the existing prototype, is optimized by applying these changes in the construction of the device and conducting experiments, and its beam diameter is reduced by 40% to be more focused.

An experimental and computational study of the secondary electron yield (SEY) of copper foam is presented. Ray-tracing Monte Carlo (MC) simulations, based on primary electron transport and interactions with the electron system in solid and foam-type copper, are also included. The 3D reticulated foam geometry is explicitly represented in the MC model. This allows the influence of the complex copper surface on the energy and angular dependence of the SEY to be determined. Experimental measurements of SEY were performed in a high-vacuum electron gun chamber. Solid copper and copper foam with 100 pores per inch and a 4.6% volume fraction were tested for energy and angular dependence of SEY. Incident angles were varied from 0 ° to 75 ° and electron beam energy ranged from 20 eV to 570 eV. The agreement between MC simulations and experiments suggests that a general reduction of the SEY by around 20% is due to the interaction and subsequent adsorption of a fraction of emitted secondary electrons on the internal surfaces of the reticulated foam. Moreover, it is found that the SEY becomes nearly independent of the incident electron energy above 200 eV for steep angles of incidence (θ > 45 °). [ABSTRACT FROM AUTHOR]

The scanning electron microscope (SEM) is a powerful tool for analyzing the surface of various specimens. SEM observation at low voltage, which is typically lower than the 1 kV range, is very effective for obtaining surface information of specimens. However, at the low voltage range, resolution is restricted by the brightness and energy spread of electron sources. Therefore, to improve the resolution, a bright and monochromatic electron source is indispensable. In this work, we focused on an electron gun with a negative electron affinity photocathode using p-type GaAs and Cs–O adsorbates. The resolution of a prototype SEM was improved by approximately 16% compared with a SEM using a conventional Schottky emission (SE)-type emitter at the acceleration voltage of 1 kV. In addition, results showed that the measured brightness was as high as an SE-type emitter (∼107 A/m2/sr/V) and the estimated energy spread was less than 0.2 eV, which was narrower than that of a cold field emission-type emitter. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The energy characteristics of a high-current electron gun with a radially converging beam have been studied. The cathode unit of the gun consisted of one or two ring sections with an inner diameter of 8 cm, each of which included 18 resistively decoupled arc plasma sources initiated by discharges over the dielectric surface. It is shown that electrostatic shielding that prevents the liberation of electrons and ultraviolet radiation from cathode and anode plasmas to the space behind the cathode decreases the probability of the breakdown development along the resistors of arc plasma sources and increases the beam pulse energy released in the anode approximately two times. In the case of two-sectioned cathode unit, the width of the beam autograph on the anode (melting trace) was ~7 cm at an axial distance between the centers of the sections of 4 cm. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to implement the electron beam melting technologies the E.O. Paton Electric Welding Institute of NASU developed a multifunctional electron beam unit UE-5810 of megawatt class, designed for producing ingots of titanium and its alloys of up to 20 tons weight. Description of a multi-purpose universal electron beam unit UE-5810 and its specification are given. Functional features of the components of the unit, technological fixtures and electron gun are described. Electron beam unit UE-5810 is a reliable highly efficient installation of industrial type for melting highly reactive metals and alloys, as well as treatment of the produced ingots by surface melting. 12 Ref., 8 Fig. [ABSTRACT FROM AUTHOR]

We consider an example of implementation of a multi-barrel gyrotron. The simplest scheme of the multi-barrel gyrotron combines the advantages of both the canonical gyrotron and the gyrotron with the near-axis beam as the system of formation of helical electron beams and efficient selection of modes synchronous with high gyrofrequency harmonics, respectively, and is attractive from the viewpoint of applications that require moderate power levels. The design of a multi-barrel gyrotron with the possibility of simultaneous generation at frequencies of 263, 395, and 526 GHz is presented. Additionally, the possibility of generating the radiation at a frequency of 594 GHz is considered. Such frequencies are required for DNP/NMR facilities with proton Larmor frequencies of 400, 600, 800, and 900 MHz, respectively. Along with the conventional scheme of radiation output towards the collector, the features of the scheme with the radiation output toward the electron gun are considered. [ABSTRACT FROM AUTHOR]

Summary: We report on our progress to develop and optimize electron sources for practical applications. A simple fabrication process is introduced based on a wafer dicing saw and a wet chemical etch step without the need for a clean room. Due to the formation of crystal facets the samples show a homogeneous geometry throughout the array. Characterization techniques are developed to systematically compare various arrays. A very defined measurement procedure based on current controlled IV‐sweeps as well as lifetime measurements at various currents is proposed. To investigate the current distribution in the array a commercial CMOS detector is used and shows the potential for in depth analysis of the arrays. Finally, a compact hermetically sealed housing is presented enabling electron generation in atmospheric pressure environments. [ABSTRACT FROM AUTHOR]

We present the design and performance of a compact ultrafast electron diffraction instrument. The diffractometer provides a means of examining time-resolved ultrafast dynamical properties of solids. The system's utilization is discussed in terms of instrument parameters and diffraction data from selected condensed matter samples. The difractometer's performance is highlighted in terms of detection sensitivity, instrumental temporal resolution, and the electron beam transverse coherence length. Following specific details of the construction, we present a practical discussion of parameters such as repetition rate and provide advice on general construction approaches for laboratory-based, keV ultrafast electron diffractometers. In addition, design guidance for constructing a compact electron gun source that is well-suited for studying diffraction from hard condensed matter is given. A unique data acquisition scheme, utilizing high laser repetition rates, is presented. [ABSTRACT FROM AUTHOR]

In this work, we present observations about the transport of 15.2 keV electrons with a beam current of 21 μA through macroscopic dielectric capillaries. These capillaries are made of borosilicate glass with an inner diameter of about 6 mm, and samples with a bending angle of 90° and 360° were investigated. The electron gun was adjusted, and the beam injected into the capillary had a current of 21 μA and a divergence half angle of about 0.75°. A retarding field analyzer (RFA) was installed at the outlet of the capillary to collect the transported current and to investigate the particle energy of exiting electrons (Fig. 1). The transport of electrons to the outlet occurred nearly instantaneous in both capillaries, and the RFA at the outlet detected a current of around 20 μA for both capillary samples resulting in a transmission coefficient of over 95%. Energy measurements showed that the particle energy at the outlet is only at several electron volts, which reveals that electrons lost almost all of their incident energy while traveling through the capillary. A large amount of exiting particles are most likely secondary electrons emitted from the capillary sample. The fact that transmission coefficients for both samples are similarly high, and that the particles can still be transported through the 360° capillary although most of their energy is already lost at 90°, results in many questions that shall be investigated in further studies. The capillaries showed a blueish glow during electron transmission due to cathodoluminescence effects. [ABSTRACT FROM AUTHOR]

In this paper, an angular radial extended interaction amplifier (AREIA) that consists of a pair of angular extended interaction cavities is proposed. Both the convergence angle cavity and the divergence angle cavity, which are designed for the converging beam and diverging beam, respectively, are investigated to present the potential of the proposed AREIA. They are proposed and explored to improve the beam–wave interaction capability of W-band extended interaction klystrons (EIKs). Compared to conventional radial cavities, the angular cavities have greatly decreased the ohmic loss area and increased the characteristic impedance. Compared to the sheet beam (0°) cavity, it has been found that the convergence angle cavity has a higher effective impedance and the diverging beam has a weaker space-charge effect under the same ideal electron beam area; the advantages become more obvious as the propagation distance increases. Particle-in-cell (PIC) results have shown that the diverging beam (8°) EIA performs better at an output power of 94 GHz under the condition of lossless, while the converging beam (−2°) EIA has a higher output power of 6.24 kW under the conditions of ohmic loss, an input power of 0.5 W, and an ideal electron beam of 20.5 kV and 1.5 A. When the loss increases and the beam current decreases, the output power of the −2° EIA can be improved by nearly 30% compared to the 0° EIA, and the −2° EIA has a greatly improved beam–wave interaction capacity than conventional EIAs under those conditions. In addition, an angular radial electron gun is designed. [ABSTRACT FROM AUTHOR]

This paper presents the design, prototype engineering, and initial testing of a relatively low-voltage, high aspect ratio electron gun for versatile pulsed power applications. The sheet beam, diode electron gun is designed for (23–25) kV voltage and 6 µA/V1.5, as is required for x-band klystron, as a part of a compact Klylac delivering electron beam energy in the MeV range. The gun prototype was engineered, built, and tested using a Scandinova M1-0.5 modulator. Beam loss on the anode aperture is evaluated from transient waveforms and equivalent circuit modeling. [ABSTRACT FROM AUTHOR]

An algorithm is presented that extends the application of ray optics to charged particle guns, where particles are emitted with a wide range of angles and relative energies. The extension is made possible by replacing the ray tangent as a coordinate with the directional sine, which remains finite for all take-off angles, and if necessary, by simulating the ray optics for multiple segments of the energy distribution. Consequently, an electron gun comprising a cathode, an extractor, and an anode, for example, may be characterized by its focal length, the location of its image plane, the magnification of the emission spot at this plane, and the primary and higher-order aberrations of the module, which reshape this spot. This description is realized by modeling the particle trajectories as a power series in their initial conditions and by using standard algebraic techniques, namely, the binomial and Taylor expansions, to transform the relativistic Newton's equation, which describes the evolution of the trajectories in the electromagnetic fields of the gun, into a differential equation for the evolution of the series coefficients. In addition to providing the optical parameters, the series coefficients produce an algebraic map between the particle coordinates along the gun axis and their initial values at the plane of emission, thereby circumventing the need to launch a multitude of trajectories in a particle simulator to model the source that the gun presents to the optical elements downstream. The algorithm may be enhanced in the future by incorporating some effects of space charge from the emission current. [ABSTRACT FROM AUTHOR]

A large research effort is currently ongoing within the framework of the EUROfusion consortium for the study and design of a water-cooled lithium–lead (WCLL) breeding blanket (BB). This concept will be tested in ITER through the installation of a test blanket module (TBM) and it is one of the two candidates adopted as driver BBs in DEMO. In this framework, at the ENEA research centre of Brasimone, the realization of the experimental platform, W-HYDRA, is envisaged. The platform is dedicated to the support of the development of WCLL BB and ITER TBM and the investigation of the DEMO balance of plants. One of the most important experimental infrastructures is the water-loop facility, the aim of which is to provide water at a high pressure and temperature (PWR conditions), with a sufficient mass-flow rate and power for the experimental testing of BB and TBM components. The facility will be equipped with a vacuum chamber and an electron beam gun for the reproduction of high surface heat flux on plasma-facing components. In the present work, the design of a prototypical mock-up (MU) of the WCLL BB first wall is described. The MU is used to investigate the thermal, hydraulic and structural behavior of the current first-wall design under relevant heat loads at the expected operational conditions. The delineation of the main experimental test's features and the instrumentation needed is assessed in the paper. A preliminary CFD calculation on the prototypical MU and the computational results are also presented. [ABSTRACT FROM AUTHOR]