Design and Experiments of the Sheet Electron Beam Transport with Periodic Cusped Magnetic Focusing for Terahertz Traveling-Wave Tubes

The successful transport of a sheet electron beam under the periodic cusped magnet (PCM) focusing at the terahertz frequencies is reported. The sheet beam with a current density of 285 A/cm2 is intended for the developing G-band sheet-beam traveling-wave tube (TWT) whose operating voltage is nominally 24.5 kV. A beamstick was developed to validate the design of the electron optics system, which is considered as the most challenging part for developing a sheet-beam device. A beam transmission ratio of 81% is achieved over a distance of 37.5 mm at a cathode voltage of −25.0 kV. The total current and the collector current were measured to be 125 and 102 mA, respectively. The experimental results are promising, demonstrating that the PCM scheme is capable of focusing a high-current-density sheet beam and hence can find use in the terahertz TWTs, offering the advantages of compact size and light weight.

DYNAMICS OF THE ELECTRON BEAM GENERATED BY THE MAGNETRON GUN WITH DIFFERENT CONFIGURATIONS OF THE MAGNETIC FIELD IN THE TRANSPORTATION CHANNEL

The dynamics of the dimensions of the electron beam generated by the magnetron gun in the particle transport channel and the efficiency of focusing the tubular electron beam in the gradient magnetic field are investigated. The experiments were carried out with magnetron guns with secondary-emission cathodes (cathode diameters 36 and 16 mm, anodes diameters 78 and 36 mm) at cathode voltage of 20...80 kV. Magnetic fields were created both by the solenoid and jointly by the solenoid and the permanent magnet. The dependence of the radial distribution of the beam on metal targets on the amplitude and gradient of the magnetic field along the axis of the system is inves-tigated. The possibility of controlling the beam diameter by varying the magnetic field is shown. The imprints of collimated beams were obtained experimentally on targets located at selected distances. The obtained experimental data agree with the results of numerical simulation. It is shown that with an increase in the amplitude of the gradient magnetic field, the effect of radial focusing of the beam is more pronounced.

Regularities in the formation of wear-resistant coatings on steel samples when machining them with electrical discharge

This paper considers the technology of electrical discharge machining of steel friction pairs and reports the results of experimental studies. Analysis of the experimental studies has shown that increasing the "anode-cathode" voltage leads to a sharp decrease in the micro-hardness of the surface layer. The study has also made it possible to determine the characteristic dimensions of the structural elements, the height parameters of surface roughness. The elemental composition of the resulting surface of a steel 15KHGN2TA sample differs from the composition of coatings and the surface layers of samples modified by electrical discharge machining involving various electrodes. Under the "anode-cathode" system operation mode, a thin layer of coating with a stable modified structure forms on the surface of the cathode due to dissipative processes. It is shown that the height of surface irregularities on sections after friction is higher than on the surface sections outside the friction flow, which is associated with the formation of a friction transfer film on the samples' surface. It was established that the interaction of friction of steel samples treated by electrical discharge machining forms a thin film on the surface of friction of steel samples, which leads to a change in the relief of surfaces with an increase in the height of the micro-protrusions, as well as the structuring of the transfer film in the direction of sliding. The effect of machining steel surfaces by electrical discharge on the wear resistance of metal-polymer tribosystem was established. The implementation of the devised technology could provide a significant increase in the wear resistance of metal-polymer tribojunctions

Highly Reliable Memory Operation of High Density Three-Terminal Thyristor Random Access Memory

Three-terminal (3-T) thyristor random-access memory is explored for a next generation high-density nanoscale vertical cross-point array. The effects of standby voltages on the device are thoroughly investigated in terms of gate-cathode voltage (VGC,ST) and anode- cathode voltage (VAC,ST) in the standby state for superior data retention characteristics and low-power operation. The device with the optimized VGC,ST of -0.4 V and VAC,ST of 0.6 V shows the continuous data retention capability without refresh operation with a low standby current of 1.14 pA. In addition, a memory array operation scheme of 3-T TRAM is proposed to address array disturbance issues. The presented array operation scheme can efficiently minimize program, erase and read disturbances on unselected cells by adjusting gate-cathode voltage. The standby voltage turns out to be beneficial to improve retention characteristics: over 10 s. With the proposed memory array operation, 3-T TRAM can provide excellent data retention characteristics and high-density memory configurations comparable with or surpass conventional dynamic random-access memory (DRAM) technology.

Online Prediction Method of Molten Aluminium Height in Electrolytic Cell Based on Extreme Learning Machine with Kernel Function

An online prediction method of molten aluminium height is proposed based on extreme learning machine with kernel function (K-ELM). Firstly, relevant variables that can be measured online related to aluminium liquid fluctuations were obtained by analyzing the mechanism model of aluminium liquid fluctuations. Then, the online prediction method of molten aluminium height is proposed based on kernel function and ELM, which just use the anode-cathode voltage and the anode rod current data. Finally, the data collection and experiment of 3 sets of anode rods in the 200 kA series aluminium electrolytic cells are carried out on-site. The results show that the maximum absolute error is only 0.25 cm and relative error is less than 1.4%, which satisfied the production site requirements. Compared with existing methods, it has certain advantages in real-time and prediction accuracy and meets the real-time and accuracy requirements of the actual production process on-site.

Highly Reliable Memory Operation of High Density Three-Terminal Thyristor Random Access Memory

Three-terminal (3-T) thyristor random-access memory is explored for a next generation high-density nanoscale vertical cross-point array. The effects of standby voltages on the device are thoroughly investigated in terms of gate-cathode voltage (VGC,ST) and anode- cathode voltage (VAC,ST) in the standby state for superior data retention characteristics and low-power operation. The device with the optimized VGC,ST of -0.4 V and VAC,ST of 0.55 V shows the continuous data retention capability without refresh operation with a low standby current of 0.13 pA. In addition, a memory array operation scheme of 3-T TRAM is proposed to address array disturbance issues. The presented array operation scheme can efficiently minimize program, erase and read disturbances on the adjacent unselected cells by adjusting gate-cathode voltage. The standby voltage turns out to be beneficial to improve retention characteristics: over 10 s. With the proposed memory array operation, 3-T TRAM can provide excellent data retention characteristics and high-density memory configurations comparable with or surpass conventional dynamic random-access memory (DRAM) technology.

Design of Magnetic Focusing system for a Compact Ka band Helix TWT

In this paper we discuss the design of Magnetic focusing system (MFS) for a compact helix travelling wave tube (TWT) operating in Ka-band. Issues related to the design of the magnetic focusing system have been discussed in detail along with practical measurement results. The key design parameters considered for this TWT are: the cathode voltage is around 9.3kV, beam current is 200mA and total length of the tube not more than 6 inch with minimal weight.

INVESTIGATION OF THE EFFECTS OF DIFFERENT RETROGRESSION AND RE-AGING PARAMETERS APPLIED TO THE 7075 ALLOY ON THE MICRO-ARC OXIDATION PROCESS

In this paper, retrogression and re-aging (RRA) heat treatment was applied to 7075 aluminum alloy in T6 condition at different times (30 and 90[Formula: see text]min) and temperatures (180∘C and 240∘C). While RRA heat treatments increase the corrosion resistance of the material, it does not harm its mechanical properties. On the other hand, the surface resistance of aluminum is low. Surface modifications are applied to overcome this deficiency. Among these, the micro-arc oxidation (MAO) method increases the corrosion resistance and attains excellent values in surface hardness. To better understand the RRA/MAO relationship, heat-treated (RRA) samples with four different parameters were coated with the MAO method. In this way, a ceramic oxide coating layer was created on the material surfaces. In order to determine the RRA parameter effect, the MAO process parameters are kept constant (anode voltage ([Formula: see text]): 500[Formula: see text]V, cathode voltage ([Formula: see text]): 300[Formula: see text]V, anode voltage open time ([Formula: see text]: 300[Formula: see text][Formula: see text]s, cathode voltage open time ([Formula: see text]): 200[Formula: see text][Formula: see text]s, frequency: 160 coating with Hz, and process time: 20[Formula: see text]min). Surface properties (coating thickness, surface roughness, surface arc duct’s structure, etc.), phase analysis (X-ray diffraction (XRD)) and microstructures (coating cross-section studies: distance-dependent hardness, coating/backing material interface character, coating porosity ratio) were examined. XRD analysis showed that the main phase of the coatings is [Formula: see text]-Al2O3. A coating layer of around 125[Formula: see text][Formula: see text]m was achieved with the growth rate of 6[Formula: see text][Formula: see text]m/min. Surface roughness was between 5.5[Formula: see text][Formula: see text]m and 8[Formula: see text][Formula: see text]m for different RRA parameters. RRA/MAO relation with the characterization made was detailed, and predictions were made for the surface properties of the material (hardness, corrosion resistance, wear, etc.).

First result of orbit verification of Taiji-1 hall micro thruster

The Hall Micro Thrusters (HMTs) use cold gas or accelerated plasma dual mode to provide ultra-precise spacecraft altitude control. They were operated in space for the first time as part of the demonstration payloads on Chinese Academy of Science’s (CASs) Taiji-1 spacecraft since September 2019. Hall Micro Thruster Assemblies (HMTAs) were the actuators in drag-free control, and will compensate the nonconservative force for gravity wave observatories. The HMTAs meet the requirements of operating at 5–100 [Formula: see text]N of thrust with 0.7 [Formula: see text]N resolution and [Formula: see text]0.6 [Formula: see text]N/Hz[Formula: see text] (0.01–1 Hz) noise to deliver the nanometer-level precision control as fast as 30 ms measured by Gravitational Reference Sensor (GRS). A transfer function model in z-domain was fit and used to filter HMTs cathode voltage to predict GRSs thrust noise response. Simulations of a single or dual-frequency disturbance and the corresponding compensation demonstrated that HMTAs could deliver the required thrust profile expected. The capability to meet the requirements of thruster noise in drag-free control is critical for future missions because the acceleration noise on test mass directly relates to the gravity wave signa l. Preliminary in-orbit verification of Taiji-1 has showed HMTAs’ great potential in future, and the data in the experiments are presented in this paper.

Tribological researches of electroerosive processing of steel details of cars

The article considers the technology of electroerosive treatment of steel friction pairs and presents the results of experimental studies. Analysis of experimental studies has shown that an increase in the anode-cathode voltage leads to a sharp decrease in the microhardness of the surface layer. The study also allowed to determine the characteristic size of the structural elements, the height parameters of the surface roughness. The elemental composition of the initial surface of the sample made of steel 15HGN2TA differs from the composition of the coatings and surface layers of the samples modified by electroerosive treatment with different electrodes. In the mode of operation of the "anode - cathode" system on the cathode surface due to dissipative processes, a thin layer of coating of a stable modified structure is formed. It is shown that the height of surface irregularities in the areas after friction is higher than in the areas of the surface outside the friction track, which is associated with the formation on the surface of the samples of the friction transfer film. It was found that the frictional interaction of steel samples treated by electroerosion method forms a thin film on the friction surface of steel samples, which leads to a change in the topography of surfaces with increasing height of microroughnesses and structuring of the transfer film in the sliding direction. The influence of electroerosive treatment of steel surfaces on the wear resistance of the metal-polymer tribosystem was established and the optimal treatment modes were obtained: voltage U = 145-150 V, capacitor capacity C = 225-230 μF, treatment duration t = 3-4 min / cm2, providing the greatest reduction in speed wear of the polymer counterbody and recommended in the development of technological processes of electroerosive treatment.