Electron Beam Source Research Articles

Solving the auroral-arc-generator question by using an electron beam to unambiguously connect critical magnetospheric measurements to auroral images

An active mapping mission is described that unambiguously connects measurements in the Earth's magnetosphere to visible aurora in the atmosphere. The core of the mission is an electron-beam source operated on a spacecraft in the equatorial magnetosphere, with the electron beam traveling along the Earth's magnetic-field lines to the atmosphere, depositing its energy to create an optical beam-spot in the atmosphere at the footpoint of the spacecraft's magnetic-field line. This optical spot can be imaged by ground-based cameras, putting the location of the spacecraft's magnetic footpoint into the context of the optical aurora. Scientific instruments carried on the spacecraft make critical measurements of the properties of the magnetosphere at the locations where the magnetosphere powers the aurora, allowing the determination of the plasma-physics mechanisms by which the magnetosphere drives the aurora, in particular answering the outstanding question of how the magnetosphere drives low-latitude auroral arcs. Long-standing questions in magnetosphere-ionosphere coupling that have not been answered because we could not unambiguously connect locations in the magnetosphere with their image in the ionosphere will finally be addressed. In this paper the properties of a “standard” growth-phase auroral arc are collected, theories of the magnetospheric generation of auroral arcs are reviewed, and critical magnetospheric measurements to discern the mechanisms that drive auroral arcs are determined. Further, the plasma physics of the experiment is investigated, including spacecraft-charging mitigation, beam stability, beam scattering, and electron orbit theory. Tradeoffs (keV versus MeV) concerning the energy of the electron beam are enumerated.

Preparation and comparative study of eco-friendly anticorrosion inhibitors based on aliphatic and aromatic compounds for electron beam curable steel coatings

PurposeIn this paper, two promising corrosion inhibitors based on natural and eco-friendly materials such as peanut fatty acids (PFA) were prepared and challenged with a common efficient commercial inhibitor. Two amino derivatives based on aliphatic and aromatic compounds such as 2-amino-2-methyl-1-propanol (AMP) and 2-amino-2-phenyl-1-propanol (APP), respectively, were used and reacted with PFA under controlled conditions to produce the corrosion inhibitors. The prepared inhibitors, namely, PFA-AMP (inhІ) and PFA-APP (inhІІ), were confirmed and characterized by Fourier transfer infrared spectroscopy, acid value determination and viscosity measurements.Design/methodology/approachFirst, different coating formulations free from any inhibitors were prepared and irradiated under different doses of electron beam source to select the best dose. Several concentrations of synthesized anticorrosion materials were then added to coating formulations to estimate them as anticorrosion materials for mild steel panels. Then, all formulations were coated and polymerized at a dose of 10 kGy. The corrosion tests, weight loss and water uptake were studied for all films after immersion in 3.5% sodium chloride. Moreover, the chemical and physico-mechanical properties were determined for all films.FindingsThe results exhibited that the different concentrations of two inhibitors did not show any significant change on the different properties of all films, and the best concentration, which gives the better protection for steel panels, was to be 1.0 g for two inhibitors.Originality/valueIt was found that the protection efficiency of the inhІ is better and higher than that of the inhІІ and also of the commercial inhibitor with the following order: inhІ > commercial inhibitor > inhІІ.

First demonstration of a cryocooler conduction cooled superconducting radiofrequency cavity operating at practical cw accelerating gradients

We demonstrate practical accelerating gradients on a superconducting radiofrequency (SRF) accelerator cavity with cryocooler conduction cooling, a cooling technique that does not involve the complexities of the conventional liquid helium bath. A design is first presented that enables conduction cooling an elliptical-cell SRF cavity. Implementing this design, a single cell 650 MHz Nb3Sn cavity coupled using high purity aluminum thermal links to a 4 K pulse tube cryocooler generated accelerating gradients up to 6.6 MV m−1 at 100% duty cycle. The experiments were carried out with the cavity-cryocooler assembly in a simple vacuum vessel, completely free of circulating liquid cryogens. We anticipate that this cryocooling technique will make the SRF technology accessible to interested accelerator researchers who lack access to full-stack helium cryogenic systems. Furthermore, the technique can lead to SRF based compact sources of high average power electron beams for environmental protection and industrial applications. A concept of such an SRF compact accelerator is presented.

Etching of Si3N4 induced by electron beam plasma from hollow cathode plasma in a downstream reactive environment

An etching system based on the interaction of electrons extracted from a direct current hollow cathode (HC) Ar plasma and injected toward an Si3N4 covered silicon substrate located in the downstream reactive environment created by an additional remote CF4/O2 plasma source was developed and evaluated. By controlling the properties of the injected beam electrons, this approach allows to deliver energy to a surface functionalized by exposure to reactive species and initiate surface etching. The energy of the primary beam electrons is controlled by the acceleration voltage relative to the HC discharge. Ar atoms flow from the high-pressure HC discharge into the low pressure downstream reactive environment in the process chamber. For an acceleration voltage greater than the ionization potential of Ar and/or process gas species, the energetic primary beam electrons produce a secondary plasma in the process chamber and can also cause additional dissociation. The authors have characterized the properties of the secondary plasma and also surface etching of Si3N4 as a function of process parameters, including acceleration voltage (0–80 V), discharge current of the HC discharge (1–2 A), pressure (3.5–20 mTorr), source to substrate distance (1.5–5 cm), and feed gas composition (20% and 80% O2 in CF4/O2). The electron energy probability function measured with a Langmuir probe about 2.5 cm below the extraction ring suggests several major groups of electrons for this situation, including high energy primary beam electrons with an energy that varies as the acceleration voltage is changed and low-energy electrons produced by beam electron-induced ionization of the Ar gas in the process chamber. When a remote CF4/O2 plasma is additionally coupled to the process chamber, Si3N4 surfaces can be functionalized, and by varying the energy of the beam electrons, Si3N4 etching can be induced by electron-neutral synergy effect with plasma-surface interaction. For conditions without beam electron injection, the remote plasma etching rate of Si3N4 depends strongly on the O2 concentration in the CF4/O2 processing gas mixture and can be suppressed for O2-rich process conditions by the formation of an SiONF passivation layer on the Si3N4 surface. The combination of the HC electron beam (HCEB) source with the remote plasma source makes it possible to induce Si3N4 etching for O2-rich remote plasma conditions where remote plasma by itself produces negligible Si3N4 etching. The electron enhanced etching of Si3N4 depends strongly on the O2/CF4 mixing ratio reflecting changing arrival rates of O and F species at the surface. Optical emission spectroscopy was used to estimate the ratio of gas phase F and O densities and found to be controlled by the gas mixing ratio and independent of HCEB operating conditions. At this time, the detailed sequence of events operative in the etching mechanism is unclear. While the increase of the electron energy is ultimately responsible for initiating surface etching, presently, the authors cannot rule out a role of ions from the simultaneously produced secondary plasma in plasma-surface interaction mechanisms.

Plasma electron source for generating a ribbon beam in the forevacuum pressure range.

We describe a plasma-cathode electron beam source based on a hollow cathode glow discharge and operating in the forevacuum pressure range that produces a steady-state ribbon beam. The electron beam is generated in the pressure range of 10-30 Pa. A multi-aperture electron extraction and beam formation system is used to provide beam stability and enhanced uniformity of beam current density, allowing the use of this kind of device for beam-plasma surface modification over relatively large areas.

Microstructure modification and corrosion improvement of [formula omitted] steel induced by pseudospark electron beam treatment

The pseudospark electron beam is a kind of pulsed electron beam characterized by fast and stable repetitive operations. It is able to achieve high rate of energy rise and plasma quenching. Thus, when used as an intense electron beam source for material processing, some unique properties are induced. The mechanism analysis of microstructure modification and corrosion improvement of AISI1045 steel treated by pseudospark electron beam are investigated. Results show that the amorphous phase is formed on the top surface of melted layer. The treated layer is several microns deep with nonuniform interface. Besides, material’s grain sizes are significantly reduced after pseudospark treatment. The average grain size in the heat affected zone is smaller than that in the melted zone, which is attribute to the combination effect of temperature-induced dynamic thermal stress fields and the highest temperature gradient. Furthermore, electrochemical impedance spectroscopy (EIS) and potential polarization analysis are used to study the corrosion behavior of samples pre and post pseudospark electron beam treatment. The improvement of corrosion resistance is due to the combination effects of the formation of austenite, the removement of impurities during the electron beam surface treatment process and the formation of the amorphous phase acted as a homogeneous passive film.

Obtaining of High-Power Electron Beams in a Plasma Anode Source Powered by the Marx Generator with Matched Loads

Experiments have been carried out to obtain high-power microsecond electron beams with high energy using an electron beam source with an explosive emission cathode and a plasma anode. The beam was formed and transported in a longitudinal magnetic field. The voltage source was the Marx generator with stages based on artificial long lines with matched loads connected to them. The possibility of realization of operation modes of the electron beam source with quasi-constant values of the accelerating voltage and current without highcurrent arc discharge formation in the interelectrode gap is demonstrated. Electron beams with circular and rectangular cross sections of ~100–200 cm2 with current up to 1–1.5 kA and duration of 5 μs were obtained at a quasi-constant accelerating voltage of 200 kV. The rotation of the beam around its axis was recorded. The possibility of electron beam extraction through a foil window into the atmosphere has been tested.

Forevacuum-pressure plasma-cathode high-power continuous electron beam source.

We describe a plasma-cathode electron beam source based on a hollow-cathode discharge that is capable of generating a 9 kW dc electron beam at an accelerating voltage of 20 kV, with helium as a working gas at a pressure of 30 Pa. A test run of ∼50 operational hours did not indicate any significant degradation of the electron source extraction system or other structural components, and we estimate the operational lifetime of the source at about 100-120 h.

Correlative Study of Enhanced Excitonic Emission in ZnO Coated with Al Nanoparticles using Electron and Laser Excitation

Recently, metal nanoparticle surface coatings have been found to significantly enhance the ultra-violet luminescence intensity from ZnO, providing a viable means to mitigate optical losses and improve LED performance. Although there is general agreement that resonantly excited Localized Surface Plasmons (LSPs) in metal nanoparticles can directly couple to excitons in the semiconductor increasing their spontaneous emission rate, the exact mechanisms involved in this phenomenon are currently not fully understood. In this work, LSP-exciton coupling in bulk and nanostructured ZnO coated with a 2 nm Al nanoparticle layer is investigated using correlative photoluminescence and depth-resolved cathodoluminescence and time-resolved photoluminescence spectroscopy. Temperature-resolved cathodoluminescence and photoluminescence measurements from 10 K to 250 K show free exciton (FX) emission enhancement factors up to 12x at 80 K, and reveal that the FX couple more efficiently to the LSPs compared to the localized donor-bound excitons. A strong polarization dependence between the LSPs and FX is observed where FX transitions are more strongly enhanced when polarized in the same direction as the electric field of the incident excitation, which is different for laser and electron beam sources. This result indicates that selective enhancement of the excitonic emission peaks in the ZnO coated with Al nanoparticles can be achieved by choosing the appropriate ZnO substrate orientation.

Development of high performance, high-current pulsed electron beam sources

As a core part, the performance of a high-current electron beam source is inevitably essential for high-power sources and accelerators. The attractive features are high-electric field vacuum interface, high quality high current density electron emission, and high peak thermal load collector, which are compatible with high repetition rate operations. This paper presents an optimized ceramic insulation structure with hold-off voltage pulse of 600 kV, 100 ns, and 5 Hz. Mechanisms and surface improvements are developed. Large-scale, well-aligned SiC nano-wires as high-current, pulsed electron beam emitters are explored. They show an superior advantage on cathode lifetime and emission quality. In addition the thermal control and cooling methods for a repetitively operated high current collector are gathered, and the specially designed device can work stably with a heat flux of 1012 W/m2. These efforts make solid contributions to the HPM sources for practical use.

Effect of Tapered Interelectrode Gap Region on Pseudospark-Sourced Electron Beam Emission

In this article, a comparative experimental and simulations analysis has been carried out to understand the role of tapered gap region on current density and energy of pseudospark (PS)-based electron beam emission. These studies have been performed for 5-gap and 8-gap regions in a tapered multigap multiaperture-based PS electron beam source, keeping the same electron beam fill factor, and other geometrical parameters identical. The source has been operated in a self-breakdown mode. Around four-times increase in the beam current has been observed in the 8-gap case at the fixed applied gap potential ranging between 20 and 25 kV, whereas the tapered interelectrode gap angle has been reduced from 7.5° to 4.5°. The field penetration inside the hollow cathode cavity and tapered region have also been analyzed using simulations, and the obtained results are explained based on built-up space charge in these regions.

Developments of Pulsed Electron Beam Sources for High-Power Microwave Applications

High-current pulsed electron beam sources are the core components of high-power microwave systems. In order to meet the requirements of future applications, one needs to improve the performance of electron beam sources in terms of vacuum insulation, beam transportation, and thermal management. In this paper, we report about our recent progress in the development of high-current vacuum electron beam sources. In order to meet the vacuum maintenance requirements of high-power microwave tubes, a high-electric field ceramic vacuum interface is designed and fabricated based on the ceramic metal brazing technique. In our experiments, a stable operation of the ceramic vacuum interface is demonstrated in the 10 Hz repetition mode with withstand voltage of larger than 600 kV and pulse width of about 100 ns. Besides, a cold cathode is developed using SiC nanowires, and an average beam current density of 1.2 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is achieved under the electric field strength of 90 kV/cm. Compared with traditional velvet cathodes, the characteristics of the SiC nanowire cathode, such as macro-electrical stability, emission uniformity, and operating life have been significantly improved. Furthermore, a high-current electron beam collector has been developed for relativistic backward wave oscillator tubes. A spiral flume is designed in the collector to meet the requirement of both high specific energy and low flow rate. It shows that the withstand heat flow density is in the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> W/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is suitable for the long pulse and repetitive operation of the system. These results represent a significant step towards the practical application of long-life high-power microwave systems.

Developing a desk-top electron beam micro-machining system in the low- pressure argon atmosphere

Electron beam machining (EBM) is a well-established technology for various industries. Conventional EBM systems use high-voltage for electron beam generation. The EBM could be used for various processing such as drilling, welding and surface modification by converting kinetic energy of electrons to thermal energy of the substrate. The core technology of EBM is electron beam generation. Traditionally, magnetic lens systems are used to focus the electron beam and magnetic coils are used for beam deflection. However, most EBM systems available on the market are designed for macro size work-piece machining purposes. These machines have large chambers and equipped with high power supplies. Thus causes difficulty for micro-machining on small work-pieces. Therefore, in order to perform micro-machining for tiny work-piece, a desk-top EBM system with a vacuum chamber smaller than 5 L was developed dedicated for micro machining processes. A transformer of microwave oven is used as power supply. As an electron beam source by using concave cathode, which focuses the resulting electron beam in argon ambient. Argon ambient also allows to avoid contamination during the process of machining. In order to obtain excellent results of micro machining operation on smaller work-pieces, the electron beam behavior of the desk-top EBM was investigated in this study. The experimental results show that dissimilar materials welding, small hole drilling and surface modification could be carried out by this desk-top EBM. It is expected that the desk-top EBM can be used for commercial applications especially for micro machining in near future.

О роли рассеяния электронного пучка в аддитивных технологиях

The prospects of using combined-type installations equipped with laser and electron-beam sources in the field of additive technologies are shown. The problem of broadening of the electron beam acting on the surface of the workpiece in a vacuum medium due to its scattering by particles of the evaporating material is considered. An analytical solution is obtained of the paraxial equation of the envelope of an electron beam undergoing scattering in the atmosphere of evaporated particles. The conditions are established that ensure stable transportation of the electron beam to the surface to be treated.

Electron–beam ion trap/source for ion–molecule collisions in the non-perturbative regime

SynopsisAn Electron Beam Ion Trap and Source has been installed at the Indian Institute of Science Education and Research Pune. The source, manufactured by Dreebit GmbH, will provide ions up to Ar16+ at energies up to 30 keV/q. These will be used for studying ion-molecule collisions in the non-perturbative regime.

Effects of Pseudo-spark Discharge Pulsed Electron Beam Irradiation on the Microstructure and Properties of 6061 Aluminum Alloy

The evolutions of the microstructure and properties of 6061 aluminum alloy irradiated by the pulsed electron beam generated by pseudo-spark discharge is the main focus of this paper. The pseudo-spark discharge is a low-pressure, transient discharge which has been recognized as a high efficient electron beam source with the rapid current growth of ~1012A/s, high power density of ~109W/cm2, short-duration pulse of 102~103ns and self-focusing beam diameter of 0.5~6mm. These characteristics enable the material treated by the pseudo-spark pulsed electron beam to melt and cool rapidly, and form the fine grain structure. In this work, the evolutions of the micromorphology and surface properties of 6061 aluminum alloy and the influences of the beam parameters are investigated and analysed. The corrosion resistance of the surface is investigated by the electrochemical corrosion experiments. The mechanism of the “crater” in the surface microstructure formed by the pseudo-spark pulsed electron beam under varying beam accelerating voltages is also analysed and discussed. The experimental results in this paper demonstrate that the re-melting layer of the material surface appears after the given pseudo-spark pulsed electron beam irradiations, and "large crater" morphology forms under higher voltage. The homogenization of the element distributions on the surface and reduction of the impurity on the re-melting layer after given pulsed electron beam treatments are capable of improving the mechanical properties of the alloy workpiece surface, and the corrosion resistance of the surface is also increased after given pulsed electron beam treatments.

Forevacuum plasma source of ribbon electron beam with a multi-aperture extraction system

The article presents the results of modernization of the accelerating interval of the forvacuum plasma electron source. The source generates an electron beam in the form of a sheet at pressures of 10–30 Pa. To increase the homogeneity, a multi-aperture extraction system was used. The optimal distances between the anode and the extractor, as well as the ratio between the cell sizes of the multi-aperture system, allowing to obtain a homogeneous electron beam width of 30 cm are determined.

Formation of pulsed large-radius electron beam in the forevacuum pressure range by a plasma-cathode source based on arc discharge

The research on generation and propagation of large-radius low-energy (up to 10 keV) electron beam with millisecond pulse duration by the plasma-cathode electron source in the forevacuum pressure range (3–30 Pa) is presented. An arc discharge with cathode spot has been used to generate emission plasma with millisecond pulse duration. Large hollow anode and ball-shaped redistributing electrode have provided formation of arc plasma with emission surface of 100 cm2; emission plasma boundary has stabilized by metallic mesh. It is established, that gas type and gas pressure affect the parameters of the arc discharge. In case of gases with greater ionization cross section (argon, nitrogen), an increase of gas pressure has led to a decrease of arc voltage and to an increase of emission plasma density. Gas with small ionization cross section (helium) had weak effect on the arc discharge parameters. An increase of emission window in the anode has provided an increase in radius of the electron beam and an increase of efficiency of electron extraction from the arc plasma; on the other hand it has led to an increase of influence of back-streaming ion flow on the electron emission and led to a decrease of maximal operating gas pressure. Reducing the geometric transparency of the emission mesh, as well as the use of gas with small ionization cross section have provided an increase in the maximal operating pressure of the source of large-radius electron beam. It is established, that in the forevacuum pressure range, large-radius electron beam is efficiently generated in the investigated range of distances from the extractor up to 35 cm.

Atomic Structure Probing of Thin Metal Films via Vacuum Holographic Microscopy

A vacuum holographic microscope is designed to probe the atomic structure of thin metal films. The experimental setup is based on the use of a source of a monochromatic low-energy electron beam induced by a tip cathode spaced from the sample at a distance of several tens of nanometers. The visual resolution of atoms of the object requires a microscope magnification of at least 105, which necessitates high-accuracy movement of the electron source. The parameters of principal nodes of the microscope, which are responsible for the generation and recording of useful signals, are studied and optimized, as well.

Single-pass non-destructive electronic detection of charged particles.

We have devised an experimental method and apparatus for the simultaneous nondestructive determination of the absolute ion number, ion kinetic energy, and length of bunches of charged particles. We have built and operated a corresponding electronic detector that is based on induced charges and their subsequent low-noise amplification at cryogenic temperatures. We have performed measurements with bunches of low-energy highly charged ions from an electron-beam ion source that show the capability of the methods and their implementation. We discuss requirements for, and applications of, such detectors with a particular view on the obtainable information and their sensitivity.