Electron Optical System Research Articles

Universal main magnetic focus ion source for production of highly charged ions

A novel room-temperature compact ion source has been developed for the efficient production of atomic ions by means of an electron beam with energy Ee and current density je controllable within wide ranges (100eV ≲Ee≲60keV, 10A/cm2≲je≲20kA/cm2). In the first experiments, the X-ray emission of Ir64+ ions has been measured. Based on a combination of two different techniques, the device can operate both as conventional Electron Beam Ion Source/Trap and novel Main Magnetic Focus Ion Source. The tunable electron-optical system allows for realizing laminar and turbulent electron flows in a single experimental setup. The device is intended primarily for fundamental and applied research at standard university laboratories.

Calculating a multipole cylindrical electrostatic system

The results of simulations of a multipole electron-optical system has been considered. The electrodes of the system consist of an even number of identical parts of one circular cylinder that is cut parallel to the generatrix with infinite length. To determine the potential distribution, the Laplace equation has been solved by the method of variable separation in the polar coordinates. All of the geometrical dimensions of the system and the number of electrodes are parameters of the problem.

Study of electron beam uniformity in large-area multi-aperture diode with arc plasma cathode

The use of plasma emission cathode in the conjunction with a multiple apertured electron optical system (EOS) is promising for the multi-MW class electron beams of a large cross-sectional area. In a multi-aperture source, the beam parameters could be raised simply due to increase of the number of apertures (i.e. an effective emission area), if a uniformity of the electron emission over a large-area plasma cathode is ensured. In the presented paper, the cross-sectional distribution of the emission current density was investigated using the X-ray diagnostic technique for two versions of the diode-type EOS, with electrodes performed as flat molybdenum “grids”. The first one had 241 apertures arranged hexagonally inside a circle with a diameter of 8.3 cm and the second had 499 apertures within a circle of 11.8cm diameter. The emission plasma is produced using a single arc-discharge plasma generator placed on the axis at 20 cm from the EOS. It was demonstrated that multi-aperture systems with a single on-axis plasma generator can be effectively employed to obtain large-area beams, even in the presence of the guiding magnetic field. All apertures are emitting in the 499-apertured EOS. The beam current density is quite uniform up to the radius 2.5cm and gradually decreases to the periphery.

The principle of similarity of trajectories for the motion of charged particles with different masses in electric and magnetic fields that are homogeneous in Euler terms

An electric field with potentials that is homogeneous in Euler terms satisfies the principle of similarity of trajectories that was derived by Yu.K. Golikov. Such fields are a useful tool for the development of electron and ion optical systems with unique properties. In this paper, the principle of similarity of trajectories is generalized to the case of a magnetic field and a combined electric and magnetic field that are homogeneous in Euler terms.

Electron motion analysis of a radial-radiated electron beam in a radial-line drift tube with finite magnetic field conducted

Radial-radiated electron beam is widely employed in radial-line structure microwave devices. The quality of the electron beam has a crucial effect on the operating performance of these devices. This paper analyzes theoretically this electron motion in a radial-line drift tube with finite magnetic field conducted. The beam width, spatial period, and fluctuation amplitude are quantitatively analyzed with different beam current parameters. By the particle-in-cell simulation, we examine the theoretical analysis under the condition of a designed realistic coil configuration. It indicates that the derived beam envelope function is capable of predicting the radial-radiated beam trajectory approximately. Meanwhile, it is found that the off-axial z-direction magnetic field, in spite of its greatly slight amplitude, is also one necessary consideration for the propagation characteristic of the radial-radiated electron beam. Furthermore, the presented electron motion analysis may be instructive for the design of the electronic optical system of the radial-line structure microwave devices.

Development of advanced electron optical systems for novel gyrotrons

Development of advanced electron optical systems for novel gyrotrons

Non-adiabatic electron-optical system for 170GHz/1MW/CW gyrotron

Non-adiabatic electron-optical system for 170GHz/1MW/CW gyrotron

On Studying the Possibility to Improve the Output Characteristics of W-Band Traveling-Wave Tubes

We have studied and calculated design variants of the slow-wave and electron-optical systems of a W-band traveling-wave tube. The manufactured experimental prototypes of such tubes were based on the slow-wave system of the “modified winding waveguide” type. Electric parameters of the prototypes were measured.

Analyzers of charged particles flows with different functional capabilities

Parameters of instruments developed on the basis of previously calculated different electron-optical systems for the analysis of charged particle flows were considered in the present work. Recommendations for their application in various fields of electron spectroscopy for the analysis of a solid surface were given.

Electron optics design of an 8-in. spherical MCP-PMT

This paper discusses the electron optical system of an 8-in. spherical MCP-PMT. The MCP assembly, the supporting pole and the supply voltages are carefully designed to optimize the photoelectron collection efficiency and the transit time spread. Coating the MCP nickel-chromium electrode with an additional high secondary emission material is employed to make a breakthrough on the collection efficiency. With the simulation software CST, the Finite Integration method and the Monte Carlo method are combined to evaluate the collection efficiency, the time properties and the Earth's magnetic field effects. Simulation results show that the photocathode active solid angle is over 3.5 πsr, the average collection efficiency can exceed 95% with the coated MCP and the mean transit time spread is 2.2ns for a typical electric potential of 500V applied between the photocathode and the MCP input facet. The prototype and the measured single photoelectron spectrum are also presented.

Theoretical Study of a Broadband Quasi-Optical Mode Converter for Pulse Gyrotron Devices

Theoretical investigation of a broadband quasi-optical mode converter for 330-GHz TE62 mode gyrotron application is presented. The converter consists of a Vlasov launcher and three reflector mirrors. Special considerations, including a Vlasov launcher with reasonably large aperture radius and optimized combination of two elliptic reflectors and a bifocal parabolic reflector, are the keys to achieve broadband mode converting. The optimized internal converter is well compatible with the gyrotron electron-optical system and generates Gaussian beam with efficiency higher than 80% in an extraordinary broadband range between 310 and 340 GHz. The principle of the broadband converter can also be applied to gyrotron amplifiers.

Experimental study on stress concentration of nickel-base superalloy at elevated temperatures with an in situ SEM system

The increasing research focus on micro- or nano-mechanics at high temperature poses new challenges for researchers to realize the deformation measurement by means of microscopic devices. SEM (Scanning Electron Microscope)-based optical methods are desirable approaches due to their full field, high magnification and high sensitivity. The SEM with an electron optical system is to some extent preferable for high temperature experiments compared with those traditional optical methods. In this study, a novel SEM-based measurement method aiming at the characterization of mechanical properties of high temperature alloys is proposed. By designing and employing a dual frequency grids pattern, the in-plane and out-of-plane deformation measurement of a specimen with U-shaped notch (U-notch) can be realized simultaneously at temperature up to 650°C. The mechanical parameters of the tested specimen are determined and the stress concentration effect at elevated temperatures is analyzed. The Baratta-Neal stress concentration solution is adopted to be compared with the experimental results. The measurement accuracy is also discussed in detail.

Effect of the Geometrical Shape of the Magnetic Poles and the Distance between Them on the Focal Properties of the Condenser Magnetic Lens in the Scanning Electron Microscope (SEM)

The research aims to study the effect of changing the geometric shape of the poles and the distance between them on the focal properties in the condenser magnetic lens and thus the efficiency of the scanning electron microscope through its impact on the amount of miniaturization in the electronic beam passers-through optical column system lenses as well as the amount of aberrations that contribute to reducing the clarity and precision in the resulting image for the sample to be tested. We used six condenser lenses equal in the internal and external geometry and the length of the lens as well as for the coil area and vary the poles and the distance between them to get out the best model.

Foucault imaging and small-angle electron diffraction in controlled external magnetic fields.

We report a method for acquiring Foucault images and small-angle electron diffraction patterns in external magnetic fields using a conventional transmission electron microscope without any modification. In the electron optical system that we have constructed, external magnetic fields parallel to the optical axis can be controlled using the objective lens pole piece under weak excitation conditions in the Foucault mode and the diffraction mode. We observe two ferromagnetic perovskite-type manganese oxides, La0.7Sr0.3MnO3 (LSMO) and Nd0.5Sr0.5MnO3, in order to visualize magnetic domains and their magnetic responses to external magnetic fields. In rhombohedral-structured LSMO, pinning of magnetic domain walls at crystallographic twin boundaries was found to have a strong influence on the generation of new magnetic domains in external applied magnetic fields.

Design of a Sheet-Beam Electron-Optical System for a Microfabricated <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math> </inline-formula>-Band Traveling-Wave Tube Using a Cold Cathode

A design of a sheet-beam electron-optical system (EOS) for a microfabricated $W$ -band traveling-wave tube (TWT) is presented. The proposed TWT is based on a rectangular field-emitter array (FEA) and a planar helix slow-wave structure with straight-edge connections (PH-SEC). The PH-SEC is designed to work with a 5-kV and 10-mA sheet electron beam. The particle-in-cell simulation results show that the TWT can give 3.7-W peak power at 110 GHz with a 3-dB bandwidth of 60%. The EOS consists of a novel beam-forming electrode, a novel anode, a magnetic circuit to provide solenoidal focusing magnetic field, and a depressed collector. Except for the magnetic circuit, all components are compatible with microfabrication. Moreover, the anode and the collector can be fabricated together with the PH-SEC using the same process steps. Using an FEA with the dimensions of $1000 \times 500\mu \text{m}^{2}$ , a beam of cross section $160 \times 40\mu \text{m}^{2}$ is generated and under ideal conditions 100% transmission is achieved through a 25-mm-long drift tunnel of cross section $240 \times 100\mu \text{m}^{2}$ . The effects of misalignments of the FEA, anode, and the magnetic circuit are investigated, and the limits on misalignments are determined to achieve satisfactory beam transmission.

Application of aluminum and titanium foils in low-energy wide-aperture electron accelerators

We have reported on the results of theoretical and experimental investigations of characteristics of aluminum and titanium foils used in devices to extract electron beams from wide-aperture low-energy accelerators with a high current density. The mechanical properties of foils at different temperatures and the electron beam transmission and absorption coefficients have been compared. The results of analyzing the dependences of the efficiency of the electron beam extraction from accelerators on the type of the electron–optical system, material, and thickness of the foil for various sizes of extraction windows and the same type of the slot support grids have been presented. We have proposed an analytic model for calculating the temperature of the foil in the unit cell of the support grid. The electron transmittance and absorbance, as well as the temperature regimes of the foils, have been calculated using different methods.

The concept of an electron-optical system with field emitter for a spectroscopic gyrotron

We propose a new version of the electron-optical system for a spectroscopic gyrotron, where the primary electron flux appears due to the field emission. Requirements to the choice of the design of a multi-tip cathode are substantiated. The shape of the electrodes and the geometry of the magnetic system, which provide the formation of a helical electron beam with parameters fit for the gyrotron operation are found.

Simulation of a three-millimeter-band pulse travelling wave tube

The results of numerical simulation of electrodynamic characteristics of a slow-wave structure shaped as a folded waveguide and an electron–optical system of a three-millimeter-band pulse travelling wave tube with an output pulsed power of up to 50 W are presented. The matching devices, the interaction space, and the electron–optical system are calculated, which allows determination of their constructive parameters. The effect of loss caused by the roughness of the surfaces of the walls of the electrodynamic system on the output characteristics of the device is estimated.

Cylindrical mirror energy analyzer with the input of charged particles through end-surface diaphragm

Computer simulation is used to study electron-optical properties of a cylindrical mirror analyzer with the input of charged particles through the end-surface diaphragm. Regimes with double crossing of the optical axis (two-stage analyzer) are considered to increase the linear dispersion. The external electrode of the electron-optical system under study can be divided into several insulated parts with independently controlled potentials. Such an approach allows the second-order tuning of focusing and wide-range variation in the dispersion. Optimal working regimes make it possible to increase the linear dispersion by a factor of 3–4 in comparison with the one-stage regime.

Foucault optical system by using a nondedicated conventional TEM

We have constructed an electron optical system for both Foucault imaging and small‐angle electron diffraction (SmAED) modes by using a nondedicated conventional transmission electron microscope. The objective lens is switched off as for Lorentz microscopy. An objective mini‐lens is utilized in order to make a crossover on the plane where a selected area aperture is located. The aperture works for an angular selection in the Foucault mode. The present electron optical system has two advantages: one is the independent control of the illumination and the imaging optics, and the other is the application of external magnetic fields to the specimen parallel to the optical axis with the objective lens. In SmAED mode, the maximum camera length is estimated to be approximately 1300 m. We succeeded in the observation of magnetic domain structures and SmAED patterns of the rhombohedral phase of La0.7Sr0.3MnO3 by using the present electron optical system. Copyright © 2016 John Wiley & Sons, Ltd.