Electron Optical System Research Articles

Bacterial degradation kinetics of poly(Ɛ-caprolactone) (PCL) film by Aquabacterium sp. CY2-9 isolated from plastic-contaminated landfill

Despite the identification of numerous bioplastic-degrading bacteria, the inconsistent rate of bioplastic degradation under differing cultivation conditions limits the intercomparison of results on biodegradation kinetics. In this study, we isolated a poly (Ɛ-caprolactone) (PCL)-degrading bacterium from a plastic-contaminated landfill and determined the principle-based biodegradation kinetics in a confined model system of varying cultivation conditions. Bacterial degradation of PCL films synthesized by different polymer number average molecular weights (Mn) and concentrations (% w/v) was investigated using both solid and liquid media at various temperatures. As a result, the most active gram-negative bacterial strain at ambient temperature (28 °C), designated CY2-9, was identified as Aquabacterium sp. Based on 16 S rRNA gene analysis. A clear zone around the bacterial colony was apparently exhibited during solid cultivation, and the diameter sizes increased with incubation time. During biodegradation processes in the PCL film, the thermal stability declined (determined by TGA; weight changes at critical temperature), whereas the crystalline proportion increased (determined by DSC; phase transition with temperature increment), implying preferential degradation of the amorphous region in the polymer structure. The surface morphologies (determined by SEM; electron optical system) were gradually hydrolyzed, creating destruction patterns as well as alterations in functional groups on film surfaces (determined by FT-IR; infrared spectrum of absorption or emission). In the kinetic study based on the weight loss of the PCL film (4.5 × 104 Da, 1% w/v), ∼1.5 (>±0.1) × 10−1 day−1 was obtained from linear regression for both solid and liquid media cultivation at 28 °C. The biodegradation efficiencies increased proportionally by a factor of 2.6–7.9, depending on the lower polymer number average molecular weight and lower concentration. Overall, our results are useful for measuring and/or predicting the degradation rates of PCL films by microorganisms in natural environments.

Development of G-Band Continuous-Wave Folded Waveguide Traveling-Wave Tube

A detailed development of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$G$</tex-math> </inline-formula> -band continuous-wave (CW) traveling-wave tube (TWT) with a 160-GHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot$</tex-math> </inline-formula> W product of bandwidth power is reported in the present work, in which the electron optics system (EOS), the tapered phase velocity folded waveguide (TPVFW) slow wave structure (SWS), the modified pill-box window (MPBW), and experimental results are described. The prototype of the proposed TWT is fabricated with optimized structural parameters obtained by particle-in-cell (PIC) simulations. Moreover, the experimental results show that TWT with 27-W output power at the frequency of 220 GHz at 100% duty cycle is obtained at the operation voltage of 17.1 kV and the current of 62 mA. The proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$G$</tex-math> </inline-formula> -band TWT will have broad applications in far-distance high-resolution imaging and large communications capacity.

Influence of the temperature state of the technological gun on the operation of the electron-optical system and elements on the parameters of the electron beam

Influence of the temperature state of the technological gun on the operation of the electron-optical system and elements on the parameters of the electron beam

Results of the Study of a New Generation Technological Gyrotron System With High Power and Efficiency

A series of work has been carried out to develop a new generation of technological gyrotrons on the first cyclotron harmonic with a radiation frequency of 28 GHz and a power beyond 20 kW. The generation efficiency reaches up to 55% at 6-kW power level without a system of recovery of residual electron energy. The efficiency of the entire setup is about 35% in the mode of maximum radiation power, which is achieved by using a magnetically shielded oil-cooled solenoid. The proper operation of the developed electron-optical system under conditions of a quasi-adiabatic magnetic field in the area of formation of a helical electron beam and a non-adiabatic one in the collector region is confirmed. The letter presents experimental data which is consistent with the results of numerical modeling. This allows us to further count on the implementation of generators up to the W-band frequency range using the magnetic system and high-voltage power sources.

Study of Beam–Wave Interaction in a Sub-THz Traveling Wave Tube with a Converging Sheet Electron Beam Focused by a Uniform Magnetic Field

A traveling-wave tube (TWT) with a sheet electron beam and staggered double-grating slow-wave structure (SWS) is a promising high-power, wideband terahertz amplifier. In such tubes, electron-optical systems (EOSs) with a converging sheet beam are mostly used, which allow a reduction of the cathode load, increase the lifetime, and enable operation in a continuous-wave (CW) mode. This paper presents the results of a 3D particle-in-cell (PIC) simulation of the 0.22 THz TWT driven with a converged sheet beam, which is compressed to less than 100 μm thickness in the EOS with a magnetically shielded cathode. The beam with high compression has a significant transversal velocity spread and essentially non-uniform current density distribution over the cross-section. These factors significantly affect the beam–wave interaction. We compare the performance of the TWT driven by the compressed sheet beam and by an idealized initially rectilinear beam without any velocity spread.

Analysis of a Hollow Electron Beam Focusing and Transmission

For vacuum electronic devices (VEDs), the use of a hollow electron beam (HEB) increases the beam-wave interaction efficiency and permits a prominent decrease of the cutoff voltage in the focusing-electrode controlled electron gun. To obtain an HEB electron optics system (EOS) with stable propagation, lower ripple, high compression, and good laminarity, the issues related to the HEBs transmission characteristics in a uniform magnetic field are deeply investigated in this article. The studies on the Brillouin flow, which are different from the conclusion of the previous literature, are presented. Through combining the theoretical analysis and the simulation, the distinct motion ways of each layer in the HEB are clearly exhibited in both cases of the immersed flow and the partially shielding flow. This work can provide a meaningful reference for the design of a hollow beam EOS with high transmission and compression.

Industrial safety monitoring in iron ore mining in the Kursk Magnetic Anomaly

The mining facilities of Lebedinsky GOK, Stoilensky GOK, Mikhailovsky GOK, Yakovlevsky GOK and KMAruda in the Kursk Magnetic Anomaly annually produce more than 170 Mt of iron ore, which is more than 60% of total iron ore production in Russia. Mining operations in KMA are the hazardous production facilities. High-rate mineral mining, as well as difficult geotechnical and hydrogeological conditions govern disequilibrium in the stress&ndash;strain behavior of rock mass. For preventing emergency situations at hazardous production facilities and in accordance with the federal legislation, it is required to carry out permanent geomechanical monitoring. Researchers of the Belgorod State University propose a geomechanical safety monitoring algorithm of iron ore mining in KMA. The monitoring of stability in mined-out voids in Gubkin Mine of KMAruda company is discussed. The recommendations are given for geomechanical monitoring using modern electron-optical and scanning systems. For the slope stability estimation of pitwall and dumps, the Belgorod State University has developed a package of programs OtkosKRUG, Otkos.log, Otkos1 and Slope Stability Calculator, which have passed the state certification. After updating for a few years, the programs include the recent achievement in programming, and enable calculation of safety parameters and stability factor (safety criterion) for slopes by the method of algebraic addition of forces, as is recommended by the Safety Rules for Pitwall and Dump Slopes in effect since 2021.

Experimental measurement of the meridian Petzval image plane of a streak tube.

For an electron-optical imaging system with wide beam focusing, the calculation of the field curvature can be performed only theoretically and requires the specific analytical expressions of the axial potential distribution in the streak tube and its corresponding derivatives, making the calculation cumbersome. Even when the electron trajectory is tracked using the numerical calculation method, the calculated results cannot be verified experimentally. A method for measuring the field curvature of the streak tube based on the spherical fluorescent screen is proposed for the first time, to the best of our knowledge. This method can directly measure the field curvature from the experimental image without requiring information on the internal structure of the streak tube, which is extremely useful for the design of the subsequent image reconstruction algorithm.

Electron-optical in-situ crack monitoring during electron beam powder bed fusion of the Ni-Base superalloy CMSX-4

Electron beam powder bed fusion (PBF-EB) of Ni-base superalloys such as CMSX-4 is a demanding process. Using conventional PBF-EB machines, process observation is done by mounting optical camera systems on viewing windows at the top of the build chamber. However, the concomitant metallization blocks optical observation methods with increasing build time. Therefore, build quality evaluation is normally done after the process utilizing visual inspection or subsequent metallurgical analysis. In this work, CMSX-4 is processed using a freely programmable PBF-EB machine with an electron optical (ELO) imaging system. It consists of a four-segment ELO detector and in-house developed imaging software. The ELO system works reliably for almost 30 h of build time and allows a layerwise monitoring of the build area. A comparison of in-situ ELO monitoring and the sample surfaces shows remarkable accordance. Furthermore, ELO imaging is applied to exemplarily document surface cracking over long build times. Therefore, the present study successfully demonstrates the application of ELO imaging for improved process control under the demanding test conditions of Ni-base superalloys.

Mathematical Modeling of Intense Beams of Charged Particles in Extended Electron-Optical Systems

Mathematical Modeling of Intense Beams of Charged Particles in Extended Electron-Optical Systems

Spin- and angle-resolved inverse photoemission setup with spin orientation independent from electron incidence angle.

A new spin- and angle-resolved inverse photoemission setup with a low-energy electron source is presented. The spin-polarized electron source, with a compact design, can decouple the spin polarization vector from the electron beam propagation vector, allowing one to explore any spin orientation at any wavevector in angle-resolved inverse photoemission. The beam polarization can be tuned to any preferred direction with a shielded electron optical system, preserving the parallel beam condition. We demonstrate the performances of the setup by measurements on Cu(001) and Au(111). We estimate the energy resolution of the overall system at room temperature to be ∼170meV from kBTeff of a Cu(001) Fermi level, allowing a direct comparison to photoemission. The spin-resolved operation of the setup has been demonstrated by measuring the Rashba splitting of the Au(111) Shockley surface state. The effective polarization of the electron beam is P = 30% ± 3%, and the wavevector resolution is ΔkF ≲ 0.06 Å-1. Measurements on the Au(111) surface state demonstrate how the electron beam polarization direction can be tuned in the three spatial dimensions. The maximum of the spin asymmetry is reached when the electron beam polarization is aligned with the in-plane spin polarization of the Au(111) surface state.

Sheet Electron Optical System for a 1.03-THz Traveling-Wave Tube

The electron optical systems (EOS) play a vital role in vacuum electron devices (VED). This letter reported the design and experiments of the sheet EOS for the 1.03 THz traveling wave tube (TWT). A high-current-density sheet electron beam (SEB) electron gun generating up to 20.3-mA at 22.4-kV is designed, based on the requirements of this TWT. Due to the very high operating frequency, more than 1 THz, the miniature tunnel and beam waist with a dimension of 0.05 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sup> 0.148 mm and 0.025 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sup> 0.114 mm, respectively, will lead to a very high beam current density (906.9 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). Therefore, a 1-Telsa uniform magnetic system is designed, to ensure such a high-current-density SEB passes through the 27-mm tunnel. Finally, the primary experiments indicate that 7.56-mA current reaches the collector.

Trajectory Analysis in a Gyrotron Electron–Optical System with Allowance for the Cathode Surface Roughness

Trajectory Analysis in a Gyrotron Electron–Optical System with Allowance for the Cathode Surface Roughness

Double-mode and double-beam staggered double-vane traveling-wave tube with high-power and broadband at terahertz band

In this paper, a 220 GHz broadband and high-power staggered double-vane traveling-wave tube has been designed and verified. Firstly, a planar double-beam staggered double-vane slow-wave structure is proposed. By using the double-mode operation scheme, the transmission performance and bandwidth have been almost increased with twice as the single mode. Second, to satisfy the high output power requirement and improve the stability of the traveling-wave tube, a double pencil-beam electron optical system has been designed, the 20–21 kV driven voltage and the 2 × 80 mA current are set as the design target. By using the mask portion and the control electrode in the double beam gun, the two pencil beams can be focused with a compression ratio of 7 along their respective centers with narrow distances of about 0.18 mm with good stability. The uniform magnetic focusing system has also been optimized. The stable transmission distance of planar double electron beams could reach 45 mm with the focusing magnetic field of 0.6 T, which was long enough to cover the whole high-frequency system (HFS). Then, to verify the availability of the electron optical system and the performance of the slow-wave structure, particle-in-cell (PIC) simulation has also been carried out with the whole HFS. Results demonstrate that the beam-wave interaction system can get a nearly 310 W peak output power at 220 GHz with a 20.6 kV optimized beam voltage and beam current of 2 × 80 mA, the gain is of 38 dB with the 3-dB bandwidth over 35 dB about 70 GHz. Finally, the high precision microstructures fabrication has been carried out to verify the performance of the HFS, the results show that the bandwidth and the transmission properties are in good agreement with simulation result. Thus, the proposed scheme in this paper is expected to develop the high-power and ultra-wideband terahertz band radiation source with potential applications in the future.

Analysis of evaluation index for the electron laminar properties in the electron optical system

In the simulation of the electron optical system of vacuum electronic devices, the evaluation of the electron laminar properties can only be judged by observing the electron trajectories. The quantitative evaluation index parameters for the electron laminar properties is lacking in the electron optical software. To achieve a quantitative analysis of the electron laminar properties in Egun simulations, the crossover rate evaluating the laminar properties of electron properties is presented in this paper. The simulation results show that the crossover rate index can accurately and quantitatively evaluate the quality of the electron laminar properties. When the crossover rate of electron properties is less than 3%, the designed electron optical system meets the engineering requirements. The crossover rate can be used as the target parameters in the automatic optimization of electron optical system.

Reserch on Optimization of Electronic Optical System of X-band Klystron

This paper has completed the simulation of the X-band 1 MW klystron electronic optical system, and optimized the electron gun and focusing system respectively. The electron gun adopts a single electron beam scheme. The voltage and current of the beam is 80 kV and 45 A respectively, the perveance is about 2.0 μP , and the average emission current density of the cathode is 6.81 A/ cm 2. The focusing system adopts the design of electromagnetic focusing, and the maximum magnetic field in the uniform area is about 0.33 T. The calculation results show that the distribution of the electric field lines in the electron gun area is uniform, the fluctuation of the electron beam is uniform, and the DC pass rate of the electron beam reaches 100%, which meets the design requirements.

Theoretical Analysis and Simulated Verification of Circular Beam Electron Optical System for Terahertz Vacuum Electron Devices

The micro-structure miniaturization of vacuum electron devices (VEDs) in terahertz band requires the high precision description of formation and transportation for the ultrahigh density electron beams with the novelty theoretical analysis and simulation. In this article, the 3-D spatial potential of circular electron beam formation is presented by adopting differential geometry and tensor analysis theory. The specific numerical solution of the circular electron beam potential can be obtained by establishing a moving coordinate frame, carrying out numerical calculation, series expansion with adopting of Riemann method. In order to verify the complex theory, a 0.34 THz vacuum electron tube using thin circular electron beam gun and corresponding optical system are designed and analyzed. The beam voltage and current are 23.8 kV and 0.28 A respectively, with beam channel radius of 0.16 mm and magnetic field of 5250 Gs. Using 3-D simulation of CST, the ultrahigh density electron beam can transport 30 mm with good stability. The spatial potential of numerical calculation with the obtained theoretical functions and the simulation model are compared to verify our theoretical description. Both the results are with good consistent which preliminary proves the effectiveness of the theoretical function. Furthermore, we combine the theoretical function potential with the electron beam envelope under the same coordinate frame, the detailed characteristics of ultrahigh density beam formation with the potential function can be directly understood easily, which will give the deep physical mechanics vision for the development of high power and high-efficiency terahertz tube in the future.

Design and Experiment of a Hollow Beam Electron Optics System for Ka-Band Extended Interaction Klystrons

In this article, the design and experiment of a hollow electron beam (HEB) electron optics system (EOS) for Ka-band extended interaction klystrons (EIKs) are presented. To realize the fast switch of the current emission at a low cutoff voltage, an electron gun with two focus electrodes (FEs) is chosen. The emitting surface of cathode is a ringed spherical surface. The first focus electrode (FE1) is around the cathode, and the second focus electrode (FE2) is set in the central hole of the cathode. The current emitted from the cathode surface is about 2A, when the operating voltage is 25 kV. Three simulation codes, Egun, Superfish, and CST, are used for designing the electron gun and the permanent magnet focusing system (PMFS). Some sensitivity analyses with respect to the PMFS’s critical parameters are presented. The simulation shows the dc beam transmission is 100%. The electron beam, confined by 6000 Gauss uniform field, propagates through the drift tube of 37 mm with good laminarity and small ripple. The emission current can be suppressed when the voltage of the FEs is −3.4 kV. According to the results of simulation, the Ka-band EIK had been constructed and the hot-test experiments had been fulfilled in succession. The experimental results exhibit that the dc beam transmission is about 99% and the beam can sustain 98% transmission at high frequency (HF) operation. In addition, the output power is higher than 8 kW in the bandwidth of over 100 MHz.

Electron-Optic System With High Compression of a Multiple Elliptic Electron Beam for a Miniaturized THz-Band Vacuum Electron Device

Electron-optic systems (EOSs) with high compression are required for THz-band vacuum-tube electron devices to reduce the cathode load, which is necessary to increase lifetime and enable operation in a continuous-wave (CW) mode. However, it is difficult to achieve high compression of multiple electron beams. In this article, we present the design and simulation of EOS with triple elliptic electron beam for a 0.2-THz traveling-wave tube. The triode electron gun with planar electrodes provides <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times 0.06$ </tex-math></inline-formula> -A electron beam with compression factor of 16. At the cathode, the current density is 26.31 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> while in the beam tunnel it is higher than 400 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The magnetic focusing system with 1.34-T axial magnetic field consisting of Nd–Fe–B permanent magnets and pole pieces is also designed. The numerical simulation predicts stable beam transmission at 25-mm distance.

Trajectory Analysis in a Gyrotron Electron-Optical System With Allowance for the Cathode Surface Roughness

Trajectory Analysis in a Gyrotron Electron-Optical System With Allowance for the Cathode Surface Roughness