Electron Optical System Research Articles

Design of a pulsed 0.5 THz gyrotron and preliminary test of its electron gun with field emitter

The paper presents the design of sub-THz gyrotron with field emitter and preliminary tests of its electron-optical system. In contrast with traditional tubes with thermionic cathodes, such a device can be switched on immediately, which looks promising for some applications. The theoretical investigation of mode excitation and results of trajectory analysis of the electron beam formed by the non-adiabatic electron-optical system are presented. The experimental tests of original field cathode confirm that it can stably operate at technical vacuum conditions inside the tube and provide beam current that exceeds starting current of operation mode. The output power of about 50 W at 0.5 THz has been predicted for obtained electron beam parameters.

Design of uniform permanent magnet electronic optical system for 220\xa0GHz sheet electron beam traveling wave tube

The sheet electron beam (SEB), for which is the low current density and large current, is highly attractive in the region of millimeter wave and terahertz vacuum electronic devices (VEDs). A uniform permanent magnet (UPM) electronic optical system (EOS) driven by a SEB for 220 GHz traveling wave tube (TWT) is designed in present work, in which the voltage and current for SEB is 17 kV and 0.3 A, respectively. For obtaining the stable high transmission rate EOS, the characteristics of SEB in UPM EOS are studied, including the emittance, orbital angle, and beam trajectories, which are discussed through the CST simulation. The results show that the emittances in the x-direction are varied from 0.003 to 0.016 mm rad and in y-direction are various from 1 × 10−4 to 3 × 10−4 mm rad, respectively, keeping below than 2.5 × 10−4 mm rad during transmission, which guarantees the stability of SEB in y-direction. For the design of complete EOS, the normal rectangular collector is used, in which the SEB is uniformed scattering.

Demonstration of a High-Power Ka-Band Extended Interaction Klystron

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.

A new test specimen for the determination of the field of view of small‐area X‐ray photoelectron spectrometers

Small‐area/spot photoelectron spectroscopy (SAXPS) is a powerful tool for the investigation of small surface features like microstructures of electronic devices, sensors or other functional surfaces, and so forth. For evaluating the quality of such microstructures, it is often crucial to know whether a small signal in a spectrum is an unwanted contamination of the field of view (FoV), defined by the instrument settings, or it originated from outside. To address this issue, the d80/20 parameter of a line scan across a chemical edge is often used. However, the typical d80/20 parameter does not give information on contributions from the long tails of the X‐ray beam intensity distribution or the electron‐optical system as defined by apertures. In the VAMAS TWA2 A22 project “Applying planar, patterned, multi‐metallic samples to assess the impact of analysis area in surface‐chemical analysis,” new test specimen was developed and tested. The here presented testing material consists of a silicon wafer substrate with an Au‐film and embedded Cr circular and square spots with decreasing dimensions from 200 μm down to 5 μm. The spot sizes are traceable to the length unit due to size measurements with a metrological SEM. For the evaluation of the FoV, we determined the Au4f intensities measured with the center of the FoV aligned with the center of the spot and normalized to the Au4f intensity determined on the Au‐film. With this test specimen, it was possible to characterize, as an example, the FoV of a Kratos AXIS Ultra DLD XPS instrument.

A model-driven system interface design method based on MVC pattern

In Electronic optical tracking system human-machine interface design process is used to simulate the console more digital implementation, not for a variety of interface between model design and model conversion problems and analyzing the availability of this situation, this article based on the interface of model-driven development research field, puts forward a new model based on the drive and friendly human-computer interaction interface design framework, studied how the presentation model set and using the MVC pattern of the organization’s program tools, in addition to the view model independent from the general MVC pattern, add visual information structured design module. At the same time, the feasibility and advantages of the new framework are proved by an example.

NUMERICAL SIMULATION OF MULTIBEAM SYSTEMS BY EL&ION CODE

Based on the tube method, taking into account the three second law for the current in each tube, the program EL&ION for preliminary rapid numerical analysis of the electron-optical system was developed, using which the system was developed for generating an ion beam of reactive gases with an energy of up to 50 keV and a current of 10...20 mA in the presence of high-density electron beam.

Avalanche leds based on nanostructured silicon for optical interconnections

The paper analyzes the parameters of silicon avalanche LEDs and their use for electron-optical signal transmission systems. The advantages of silicon avalanche LEDs are shown, among which high speed and compatibility with silicon technology should be highlighted. Experimental avalanche LEDs based on nanostructured silicon were fabricated and studied. The results of controlling the electroluminescence spectrum of avalanche LEDs due to the choice of production conditions to form nanostructured silicon are presented. It was found that the temperature of the substrate during the deposition of the surface nanocomposite aluminum + silicon film affected the size of the formed silicon nanoparticles determining the spectral characteristics of avalanche LEDs. This allows shifting the maximum of their emission spectrum to a shorter wavelength region of the visible range due to the forming of smaller silicon nanoparticles. The authors have developed an optical interconnection system consisting of avalanche LEDs based on nanostructured silicon and a microchannel silicon wafer used to transmit a light signal. The study of various operating modes of the developed optoelectronic system was performed and an increase in the efficiency of optocouple based on avalanche LEDs to 0.2% due to the pulsed operating mode was achieved. It is shown that the efficiency of the optocouple increases with LED current and it is the pulsed mode of its operation that is characterized by the maximum current, which is due to more efficient removal of Joule heat in the intervals between pulses, ensuring stable operation of the entire system. The results obtained open up new opportunities for the development of optical interconnections between silicon chips and silicon optoelectronics in general.

On the Effect of Transverse Thermal Velocities of Electrons in the Converging Sheet Electron Beams Formed by Guns with Partial Magnetic Shielding of a Cathode

We report on the results of investigations of the effect of the initial thermal velocities of electrons in the converging sheet electron beams formed by guns with partial magnetic shielding of a cathode. The results are presented in the form of generalized dependences, which can be used to control the thermal beam configuration with different beam parameters and focusing magnetic fields and simulate the electron-optical systems that ensure a required current flow of such beams in the transit channel.

Comparison of Large-Area Low-Energy Electron Accelerators Based on a High-Voltage Glow Discharge with Accelerators Based on Longitudinal Filaments

Abstract—A wide-aperture low-energy electron accelerator based on a high-voltage glow discharge (HVGD) is considered in comparison with accelerators based on a number of longitudinal filaments. The basic design features and advantages of HVGD-based accelerators are presented. These studies showed that it is possible to obtain high values of the density of the electron beam current extracted from the foil (56 µA/cm2) and rather high values of the beam extraction efficiency (35%) in comparison with the previously attained results. The obtained characteristics are comparable with the parameters of the accelerators based on a number of longitudinal filaments. The ability of the accelerator to operate with HVGD is demonstrated both in continuous and pulse–periodic modes without a change in its design. Various ion–electron optical systems of HVGD accelerators have been studied and the advantages of slit-type systems are shown.

Guest Editorial for the special issue on devices and circuits for millimeter‐wave and THz applications

Guest Editorial for the special issue on devices and circuits for millimeter‐wave and THz applications

OPTIMIZATION OF THE FUNCTIONAL EFFICIENCY OF THE ELECTRON-OPTICAL SYSTEM

We suggest statement of the problem of optimization (hereinafter in the information sense) of classification setting in terms of efficiency for a complex object of control and management. An algorithm to solve it has been developed using the example of autofocusing a scanning electronic microscope as part of the method of functional-statistical tests, based on assessment of the information ability of the trainable support and decision-making system. The tuning process is considered as an iterative procedure for finding the maximum informational measure of diversity of the initial (defocused) and current image classes. The disadvantage of this algorithm is the appearance of a long oscillatory process when the value of the tuning parameter changes in the range of its extreme value, which leads to a decrease in the efficiency of auto-tuning of the electronic-optical system. We propose an approach to increase the efficiency of image autofocus for the classification auto-tuning of the electronic-optical image recognition system. It is shown that the increase in efficiency is achieved by determining the increment system of the control setting parameter – the winding current of the objective lens. The Fibonacci numbers are used as the increment system. The results of experimental verification of the proposed algorithms are presented. Improving the automation of data processing in combination with methods and models of pattern recognition allows to use a hardware-software complex, which forms the basis for researching at the synthesis of artificial intelligence systems, in order to design an autofocus image system for new models of a scanning electron microscope.

Calculation algorithm of the trajectories of electrons in electrostatic and magnetostatic fields of electron-optical systems

An algorithm for numerical calculation of the trajectories of electrons emitted by plasma in the electron beam moving in axially symmetric electrostatic and magnetostatic fields is proposed. This algorithm is based on the technology of charged particle beam discretization by current tubes and the decomposition method of the computational domain. Field simulation and numerical solution of equations for particle motion are carried out with the use of quasi-structured grids.

Ways to Increase the Beam Energy Concentration in the Electron-Optical System of a Welding Gun

Possibilities of increasing the electron beam energy concentration in the electron-optical system of a welding gun characterized by a traditional scheme in which a focusing lens and a deflecting system are installed sequentially along the beam and a new scheme based on a focusing–deflecting system with combined fields are considered. A technique based on solving the paraxial equations of trajectories and calculating aberration integrals is described, which allows one to determine the total diameter of the electron beam. Based on the described methodology, a model of a new focusing–deflecting system with combined fields has been developed. It is shown that the new scheme of the electron-optical system allows one to increase the energy concentration in the region of the interaction of the beam with the material in comparison with the traditional one.

Polishing of Precision Surfaces of Optoelectronic Device Elements Made of Glass, Sitall, and Optical and Semiconductor Crystals: A Review

Studies on the development of modern methods of precision surface polishing for the production of electronic device and optical system elements from glass and optical and semiconductor crystals are reviewed. The mechanisms that underlie material removal from the workpiece surface are described for polishing with a tool with bound abrasive, mechanical polishing with polishing powder suspensions, and chemicomechanical polishing. The results of the study of the mechanism that underlies the formation of the optical surface nanoprofile during polishing are presented and the relevance of studying the regularities of ultrasmooth surface formation during chemicomechanical polishing is emphasized.

Design and Simulation of a Multi-Sheet Beam Terahertz Radiation Source Based on Carbon-Nanotube Cold Cathode.

Carbon nanotube (CNT) cold cathodes are proving to be compelling candidates for miniaturized terahertz (THz) vacuum electronic devices (VEDs) owning to their superior field-emission (FE) characteristics. Here, we report on the development of a multi-sheet beam CNT cold cathode electron optical system with concurrently high beam current and high current density. The microscopic FE characteristics of the CNT film emitter is captured through the development of an empirically derived macroscopic simulation model which is used to provide representative emission performance. Through parametrically optimized macroscale simulations, a five-sheet-beam triode electron gun has been designed, and has been shown to emit up to 95 mA at 3.2 kV. Through careful engineering of the electron gun geometric parameters, a low-voltage compact THz radiation source operating in high-order mode is investigated to improve output power and suppress mode competition. Particle in cell (PIC) simulations show the average output power is 33 W at 0.1 THz, and the beam–wave interaction efficiency is approximately 10%.

Development of a High-Power Continuous-Wave Gyrotron for High-Efficiency Technological K-Band Microwave Complexes

We analyze the possibility to create new generation continuous-wave gyrotrons operating in the Kband (at frequencies of 28-30 GHz) at the fundamental cyclotron resonance with an output power of 25–30 kW and more. For a gyrotron with a magnetically shielded solenoid, the electron-optical and electrodynamic systems have been optimized, which ensures generation with high efficiency (about 50%) at acceptable thermal loads on the key device elements. The proposed design of the gyrotron ensures long-term continuous-wave operation of the technological complex with a total system efficiency of about 35%, which is significantly superior to the existing analogs.

Preparing a Celadonite Electron Source and Estimating Its Brightness.

The electron celadonite source described here performs well in a low-energy electron point-source projection microscope in long-range imaging. It presents major advantages compared to sharp metal tips. Its robustness affords a lifetime of months and it can be used under relatively high pressure. The celadonite crystal is deposited at the apex of a carbon fiber, maintained itself in a coaxial structure ensuring a spherical beam shape and easy mechanical positioning to align the source, the object and the electron-optical system axis. There is a single crystal deposition via generation of celadonite-containing water droplets with a micropipette. Scanning electron microscopy observation can be performed to verify the deposition. However, this adds steps and therefore increases the risk of damaging the source. Thus, after preparation, the source is usually inserted directly under vacuum in the projection microscope. A first high voltage supply provides the kick-off needed to start the electron emission. The field emission process involved is then measured: it has already been observed for dozens of electron sources prepared in this way. The brightness is under-estimated through an over-estimation of source size, intensity at one energy and cone angle measured in a projection system.

A 120-kV electron welding gun with plasma cathode: vacuum and non-vacuum application

The article studies the generation of small-diameter focused electron beams using electron-optical system of a welding gun with plasma cathode. The results show that the beams always form in the electron-optical system with plasma cathode when the gas in the region of beam emission, acceleration and transportation is present. The presence of the gas causes positive volumetric charge formation during the passage of electrons. This charge electrically neutralizes the beam, and in some cases can lead to overcompensation of its electron charge. The compensation of the volumetric charge in the region of beam formation and acceleration is the principal discrepancy of an electron-optical system with plasma cathode from a thermal cathode system. It is demonstrated that the brightness of the electron beam from a plasma cathode gun meets that of the beams from a thermal cathode gun. The paper describes the electron gun featuring voltage up to 120 kV and presents images of polished samples of weld penetration in stainless steel and titanium in vacuum. The gun served as the basis of a device for ejecting electron beam into the atmosphere. It is shown that the pressure rise up to the atmospheric one is provided through two gas-dynamic stages. The main characteristics of the atmospheric gun are given.

Plasma Source for Bipolar Electron-Optical System

The paper presents the experimental study of pulsed plasma source with hollow cathode intended for bipolar electron-optical system with open-boundary plasma. The proposed configuration of the plasma source includes two ring-shaped discharge cells based on plasma thruster technology. The plasma source can operate both in a low-current high-voltage mode and a high-current low-voltage mode. The main attention is paid to the highcurrent mode which is similar to the glow discharge positive column. It is found that along with the discharge in closed electron drift the ignition of additional, non-self-sustained hollow cathode discharge with electron oscillation is possible, thus considerably reducing the voltage of the closed-drift discharge. Current–voltage characteristics of the high-current discharge are measured for these conditions. Using the double probe technique, the local plasma parameters are measured together with their spatial distribution in the discharge region. The maximum plasma density along the plasma source axis is (6.5–6.8)•1012 сm–3.

Plasma source based on ring-shaped anode layer thruster for a bipolar electron-optical system

The conceptual design of pulsed plasma source for plasma-optic application and materials modification are investigated. The source is based on plasma thruster’s technology, that were developed by Goncharov’s group in Institute of Physics (Kiev, Ukraine). The plasma device with its two modified closed-drift anode layer thrusters can operate in low-current high-voltage mode and in high-current plasma mode. Most attention in the paper is focused on the latter mode being similar to a glow discharge with a positive column. The study shows that under certain conditions, the discharge with closed electron drift can be accompanied by non-self-sustained hollow-cathode discharges with oscillating electrons which greatly decrease the auxiliary discharge voltage. Presented in the paper the current–voltage characteristics of this type of high-current discharge and the spatial distributions of plasma parameters are measured in the discharge region with double Langmuir probe techniques. The maximum plasma densities on the central cathode axis are (6.5÷6.8)×1012 cm–3.