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In this paper, a scheme by optimizing electric field distribution with a two-output structure of the extended interaction oscillator (EIOs) is proposed to permit a significant increase in the efficiency at Ka-band. The distribution of the axial electric field and the synchronous conditions are optimized to make more fast electrons of the entire two-beam EIO circuit fall into the deceleration region and transfer energy to the electric field. Simulation results show that the efficiency is firstly improved from 28 % to 41 % by optimizing the external Q ( Q e ), the beam perveance ( P t ) and the last period. To further increase the efficiency, a peak output power of 254 kW and an efficiency of 50.8 % at 54 kV voltage and 4.6×2 A current is obtained by optimizing the all-period synchronous conditions. The idea of the optimization method provides an effective way to improve the efficiency of multibeam vacuum electronic devices at millimeter-wave and higher frequencies.

As an essential vacuum electronic device for producing the microwave, the magnetron has various applications. This study developed a novel high-efficiency 12-vanes CW magnetron and anode resonance system that improved mode separation, expanded the working space of π-mode and made other modes more challenging to trigger, ultimately eliminating the possibility of mode jumping. A magnetron was simultaneously supplied with a particular quantity of anode voltage, and the cathode was generated by the electron, and high-frequency field interaction of a homogeneous magnetic field. The work efficiency of the 12-vanes CW magnetron was significantly enhanced. Given an anode voltage of 8000 V and a magnetic flux density of 3980 Gs as a consequence of particle simulation, the variation trend of a magnetron’s output power oscillation curve correlated with the development of hexagonal spokes. After a period of stable operation, the magnetron’s fundamental parameters were determined to be as follows: the primary frequency oscillation frequency was 2.466 GHz, the anode collision current was 1.08 A, the amplitude of sinusoidal oscillation was 125, the output power was 7812.5 W, and the corresponding power conversion efficiency was 90.42%. Changing the magnitude of the anode voltage or magnetic flux density resulted in a reduction in power conversion efficiency within a particular range; however, between 85% and 90% stability was maintained.

A novel method, which combines a multiple-beam extended interaction oscillator (EIO) with pseudospark-sourced (PS) sheet electron beams, is applied to generate high-power terahertz sources. For a multiple-beam EIO, the beam cross-section is significantly improved by replacing the commonly used pencil electron beams with sheet electron beams. The PS electron beams have the advantage of high current density and operate without a focus magnetic field. The volume of the cavity is larger when the EIO operates in the TM31-3π mode than in the conventional TM01-2π mode at the same operating frequency. The EIO operating at the terahertz frequency has a larger cavity volume, which means greater power capacity and lower manufacturing difficulty. For a PS multiple-beam EIO, the non-uniformity of electron beam currents is a common problem. In order to study this problem, an original high-order mode EIO driven by PS multiple sheet electron beams is presented with enhanced output power at 0.35 THz. The authors analyze electron beams with different currents through particle-in-cell (PIC) simulations. Simulation results show that the EIO can operate stably even in the case of non-uniform PS electron beam currents. When each current is 1.4 A, simulation results show the EIO’s output power of 4.9 kW at 0.35 THz. Considering the low conductivity of 1.1 × 107 S/m, the efficiency is still 1.42%.

This paper presents the first design that combines pseudospark-sourced (PS) electron beams with a multiple-beam extended interaction oscillator (EIO). The PS electron beam is an excellent choice for driving EIOs because it has high current density and does not require a focusing magnetic field. The EIO with coaxial structure adopts the method of multiple electron beams, which plays a crucial role in improving the average output power. At the same frequency, the EIO operating in the high-order TM[sub.31] -3π mode has a larger cavity size than the EIO operating in the traditional TM[sub.01] -2π mode. The high-order TM[sub.31] -3π mode solves the problem of the EIO’s manufacture at high frequency. In order to verify the above points, a G-band PS multiple-beam EIO operating in TM[sub.31] -3π mode has been designed. The beam–wave interaction particle-in-cell simulation results show that the EIO’s peak output power is 39.2 kW at 217 GHz, and that its efficiency is around 6.1%. The EIO with six pencil beams operates at a voltage of 43 kV. The total current of the six electron beams is 15 A (equally distributed among the six beams), and the corresponding current density is about 5000 A/cm[sup.2] . Considering the ohmic loss and the effect of skin depth, the conductivity used in these simulations is 2 × 10[sup.7] S/m. The design is an excellent way to improve the output power of EIO operating at high frequency.

Phase locking is an essential choice for building a coherent array, and a system of phase-locked magnetrons is relatively compact and cheaper than other microwave sources. Previous theoretical and experimental studies on phase locking are conducted using synchronized high-voltage pulses. Here, we investigate the characteristics of two phase-locked magnetrons using particle-in-cell (PIC) simulation software (CST STUDIO SUITE 2020) when two high-voltage pulses have delays. The results show that the magnetrons produced two-level RF signals because the operation could be divided into two stages. The first stage happened when one cathode emitted electrons; then, the electrons formed one spoke, traveling in synchronism with the 0-phase difference mode. Two output ports both produced half the output power of a free-running magnetron. The second stage happened after another cathode started to emit electrons, which were instantly pre-modulated by the electromagnetic field of the 0-phase difference mode produced during the first stage. In the second stage, simulations showed that pre-modulation accelerated the process of electron bunching. Eventually, two magnetrons were phase-locked, and the total output power of the two identical magnetrons nearly doubled the output power of the free-running magnetron, which demonstrated that the magnetrons were phase-locked in the high-efficiency phase-locking regime.

This paper proposes a simplistic, efficient, and low-cost method of millimeter-wave nondestructive testing (NDT) of dielectric material cracks based on millimeter-wave interference. A relationship between combining efficiency, phase difference, and amplitude difference was analyzed. We found that phase difference was the main factor that affects combining efficiency. A change in combining efficiency of more than 1% was caused by a phase-difference altering of greater than 1.2° in a specific range. A relevant model was simulated with CST, and the operating frequency and antenna spacing were optimized to enhance sensitivity of the measuring system. Then, a Ka-band NDT system was built to test the combining efficiencies of different cracks. The experimental results showed that for polytetrafluoroethylene (PTFE) plates with a thickness of 5 mm, cracks with a width of about 0.4 mm, which is about 0.07 λg, could be detected at 35 GHz. Experimental results, simulation results, and theoretical derivation are basically consistent. Large-scale online applications of this NDT method in various industries appear feasible due to the above characteristics.

This paper presents the first design that combines pseudospark-sourced (PS) electron beams with a multiple-beam extended interaction oscillator (EIO). The PS electron beam is an excellent choice for driving EIOs because it has high current density and does not require a focusing magnetic field. The EIO with coaxial structure adopts the method of multiple electron beams, which plays a crucial role in improving the average output power. At the same frequency, the EIO operating in the high-order TM31-3π mode has a larger cavity size than the EIO operating in the traditional TM01-2π mode. The high-order TM31-3π mode solves the problem of the EIO’s manufacture at high frequency. In order to verify the above points, a G-band PS multiple-beam EIO operating in TM31-3π mode has been designed. The beam–wave interaction particle-in-cell simulation results show that the EIO’s peak output power is 39.2 kW at 217 GHz, and that its efficiency is around 6.1%. The EIO with six pencil beams operates at a voltage of 43 kV. The total current of the six electron beams is 15 A (equally distributed among the six beams), and the corresponding current density is about 5000 A/cm2. Considering the ohmic loss and the effect of skin depth, the conductivity used in these simulations is 2 × 107 S/m. The design is an excellent way to improve the output power of EIO operating at high frequency.

High current density and high brightness are critical factors for high-power and compact extended interaction oscillators (EIOs) which are operated in the terahertz (THz) waveband. The pseudospark-sourced (PS) sheet electron beam, which combines merits including high current density, a relatively big beam cross-section and no requirement for the external focusing magnetic field, is a good choice for application to high-frequency EIO. The pulse generated by the PS electron beam can last around tens of nanoseconds or even less, thus the EIO’s oscillation start-up time (OST) should be short enough. This paper researched how to reduce OST in an EIO driven by the PS sheet electron beam. The authors realized that the OST of EIO was very sensitive to the gap length under the equal period. The distribution of the electric field is optimized by adjusting the length of the gap. The strong electric field strength is conducive to the beam-wave interaction, and the OST is affected by the beam-wave interaction. When the gap length reaches a suitable value, the OST becomes the shortest. The simulation results showed the EIO’s shortest OST was 8 ns and the corresponding peak output power was 2 kW at 0.19 THz, while the current density was 500 A/cm2. When current density reached 10,000 A/cm2, the shortest OST could even be 1.9 ns.

The development of multiple-beam devices is required due to the increasing demand of compact, high-frequency, and high-power vacuum devices. A Ka-band multiple-beam extended-interaction oscillator which operates in TM01 mode with a large diameter (as the value is 14.6 mm which is larger than the operating wavelength of 8 mm) to obtain high output power has been put forward. In previous studies, the performance differences of single-beam extended-interaction oscillator with different electric field uniformity can be as high as 70%. Simulation results predicted the multiple-beam device has an average output power of 7.594 kW when a total beam of 3 A, 18 kV and the uniformity parameter is 0.064. Meanwhile, it predicted that the difference of output power of multiple-beam devices with different field uniformity (corresponding uniformity parameter is within 0.064~0.278) is within 2.53% when other operating conditions are unchanged. The results show that the multiple-beam device substantially decreases the influence of the field uniformity, which is an important factor for the performance in the single-beam device. A cold test experiment has been carried out based on perturbation theory to obtain the electric field distribution curves of this device, and this provides a method for studying multiple-beam devices.

Micro-drilling in ballpoint pen tip production faces persistent challenges of tool wear and premature breakage, which limit manufacturing efficiency and dimensional accuracy. In this study, an integrated framework combining finite element simulation (FEM) and orthogonal experimental design was developed to optimize the geometry of micro twist drills. A three-dimensional FEM model was established in Deform‑3D to analyze the effects of apex angle, helix angle, chisel edge length, and chisel edge angle on cutting force and torque. Range analysis of the orthogonal design revealed that chisel edge length and apex angle were the most influential parameters. The optimal configuration (b = 0.05 mm, 2Φ = 135°, Ψ = 76.5°, β = 3°) reduced average torque by 22.2% and extended tool life by 43.9% compared with the original design, while maintaining hole dimensional accuracy within ± 0.01 mm. These results confirm FEM as a reliable predictive tool and demonstrate that the proposed FEM–orthogonal framework provides a structured and cost-effective strategy for micro-tool geometry optimization, with direct industrial applicability to precision manufacturing of ballpoint pen tips.