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Graphite is the most commonly used large-area cathode material in the high-power vacuum electron device for its long life and good repetitive-frequency performance, but its particle size selection scheme has not been elucidated. Therefore, in the present work, the explosive electron emission properties of flake graphite large area explosive electron emission cathodes with varied particle sizes are studied. The 320 mesh flake graphite has a current delay reduction of 0.2–0.9 ns compared to other samples at the same peak voltage. According to the Murphy–Good equation, the emission performance of each sample during the priming stage was calculated, and the threshold characteristics of 320 mesh flake graphite were significantly better than the other samples. After the space charge limited current is formed, the plasma expansion rate of all samples is 1.2 ± 0.2 cm / μ s with a difference not exceeding 4 % between samples. Our research provides a strong basis for the selection of raw materials for graphite based large area explosive electron emission cathodes and contributes to the development of cross-field high-power vacuum devices. [ABSTRACT FROM AUTHOR]

The cathode emission surface (CSD) defect is one of the main reasons for the performance difference in relativistic magnetron multiple pulses operation, but its impact mechanism is unclear. In this work, the kinetics model and the particle in a cell method were used to explain the influence of the emission defect effect. The results indicate that the CSD effect causes deformation of the electron sheath and reduces the current. The emission defects in the azimuthal direction − π / 2 < n φ * < π / 2 region favor the electron bunching. Moreover, the emission defects on the cathode side near the accelerator in the axial direction weaken the axial drift issues. Our work will provide a basis for the large-area cathode design and facilitate the relativistic magnetron experimental analysis. [ABSTRACT FROM AUTHOR]

This document is an erratum for the article titled "Study of cathode emission surface defects in relativistic magnetrons" published in the journal Physics of Plasmas. The erratum corrects three writing errors in the original paper, specifically in the abstract and on pages 3 and 8. These errors are related to mathematical equations and have no impact on the rest of the paper. The authors of the original article are Tingxu Chen, Tianming Li, Hao Li, Haiyang Wang, Renjie Cheng, Hao Zhou, Biao Hu, and Hao Fu. [Extracted from the article]

Humidity of proton exchange membrane fuel cell, a critical underlying variable that affects stack efficiency and durability, is quite challenging to be well controlled due to the measuring difficulty and multiple couplings with other variables. For precise humidity description and control, this paper utilizes the internal water content as the feedback signal, whose dynamic model is developed by taking into account various auxiliary couplings. Based on the mechanistic model, the dynamic responses of the internal water content are exhibited and analyzed by manipulating the external current, air compressor voltage and humidifier electrical power, respectively. It is shown that the internal water content is able to better describe the real humidity environment, in contrast with the conventional method using cathode inlet relative humidity. Furthermore, a combined feed-forward and feedback control structure is proposed to maintain the internal humidity as close to the desired as possible. Simulation results show that the proposed control method is able to maintain the fuel cell operating within the safe and efficient region, and the humidification power consumption can be reduced because of the precise and less conservative description on the internal humidity. • A control-oriented model is developed to fully describe the humidity dynamics. • The soft sensing of the water content of cathode is used as the feedback signal. • New control structure is developed to maintain the relative humidity at 100%. • The proposed control strategy prevents flooding and reduces humidification power. [ABSTRACT FROM AUTHOR]

To set up an automatic hot test platform of gyrotron traveling wave tubes (gyro-TWTs), feedback controls of proportional–integral–derivative (PID) were applied. Simulation of the controlling process of operating voltage on the gyro-TWT cathode had been carried out by MATLAB and then was verified as well as compared by the hot test experiment. The PID control on cathode–anode voltage is typical and similar to the control of beam current achieved by the heater filament. The operating voltage controlling process includes two different stages, i.e., the voltage rise and voltage maintenance phase. By optimizing the operating parameters of the PID algorithm, the simulated voltage rise has a good agreement with the one in the hot test controlling. Furthermore, PID responses after feedback control with sinusoidal and random fluctuations are, respectively, investigated. This paper indicates that the proposed strategy can easily achieve a stable operating voltage. [ABSTRACT FROM AUTHOR]

In this paper, a novel triode-type magnetron injection gun (MIG) with three emitters designed for gyrotron traveling wave amplifiers has been presented. This MIG can be operated in Ku/Ka/Q single band or Ku-Ka/Ka-Q dual band. The optimization of the MIG is accomplished by a multiobjective genetic algorithm method. It is anticipated that this MIG possesses an axial velocity spread of <5% in all the operating frequency bands. The results of sensitivity study show that this MIG can work stably within reasonable parametric windows. Velocity spreads considering cathode surface roughness and initial thermal temperature are analyzed. Cathode configuration with heat insulation chambers is introduced to cut off the thermal flow among the emitters. Thermal analysis has been performed. [ABSTRACT FROM AUTHOR]

Layered manganese oxide represents one most potential cathode for sodium-ion batteries thanks to high theoretical specific capacity, low cost and environmental friendliness. Nevertheless, its surface structure degrades owing to the hydration reaction when being stored in the humid air. Herein, Na 0.67 Mn 0.92 Cu 0.04 Fe 0.04 O 2 (NMCFO) cathode material is functionalized by tetradecylphosphonic acid (TPA) on the surface to enhance the air stability. It is demonstrated that the TPA protection layer could improve the surface hydrophobicity, and further inhibit the hydration reaction to produce residual alkali, effectively maintaining modified material's crystal structure and electrochemical performance. After 28 days of placement in the humid air, the modified material delivers a specific capacity of 94.0 mAh g−1 at 5C, and exhibits a capacity retention of 92.22% after 100 cycles at 1C. In summary, we provide an effective pathway to protect layered manganese oxide and other moisture-sensitive materials without sacrificing cell performance. [ABSTRACT FROM AUTHOR]

Herein, a series of 6BaO·1CaO·2Al 2 O 3 + x wt% Sc 2 O 3 (x = 1, 3, 5, 7, 9) impregnants were synthesized by a liquid-phase co-precipitation method and subsequent sintering at 1200 °C. The as-synthesized emissive materials were impregnated into porous tungsten matrices at 1700 °C, and their phase composition and electron emission performance were investigated. The X-ray diffraction analysis of the sintered and melted impregnated products revealed that they comprised multi-phase structures consisting of (Ba,Ca) 3 Al 2 O 6 , Ba 2 ScAlO 5 , and BaAl 2 O 4 phases. Furthermore, the addition of 3 wt% Sc 2 O 3 to the impregnated test cathodes significantly increased the emission level of the test cathode to 11.4 ± 0.6 A cm−2 at 1100 °C B (i.e., brightness temperature). The relationship between the electron emission properties and phase concentration in the impregnants was analyzed, and the results revealed that the emission performance of the cathodes deteriorated with an increase in the Sc 2 O 3 content, which could be attributed to an increase in the concentration of non-active BaAl 2 O 4 phase in the impregnants. [ABSTRACT FROM AUTHOR]

(Ba,Ca) 2 ScAlO 5 compounds are synthesized and improved emission performance is achieved by virtue of their single-phase structure and low work function. The substitution of Ca2+ for Ba2+ effectively lowers the melting points of (Ba,Ca) 2 ScAlO 5 from over 1800 °C–1700 °C when the Ca2+ substitution reaches 20 at%. During sintering, the co-precipitation precursor first reacts to form (Ba,Ca) 3 Al 2 O 6 near 912 °C before reacting with BaCO 3 and Sc 2 O 3 at the higher temperature of 1186 °C to generate (Ba,Ca) 2 ScAlO 5. Emission tests reveal that the maximum full space charge current density is 9.6 A cm−2 at 1000 °C B (brightness temperature) for the cathode impregnated with single-phase (Ba,Ca) 2 ScAlO 5. Low work function (~1.5 eV) and good emission uniformity make such a cathode promising for applications in high-power microwave devices. [ABSTRACT FROM AUTHOR]

The effects of air, hydrogen, and CO 2 and O 2 mixture sintering atmospheres on the structure, micromorphology, electron emission capability and environmental stability of 612 type barium-calcium-aluminates have been investigated. Both the 6BaO-1CaO-2Al 2 O 3 aluminates sintered in air and hydrogen crystallize in the Ba 3 CaAl 2 O 7 phase. However, the aluminates with the same composition sintered in CO 2 and O 2 mixture crystallizes in the Ba 3 Al 2 O 6 phase with a small amount of BaCO 3 reactant. The microstructure for the aluminates sintered in air and H 2 show similar features while the sample sintered in CO 2 and O 2 mixture atmosphere shows better conglomeration. Emissivity tests indicate that the divergent current density J div for the dispenser cathodes impregnated with aluminates sintering in air, H 2 , and CO 2 and O 2 mixture atmospheres are 6.0, 6.1, and 7.6 A cm−2 at 1130 °C B , respectively. Finally, environmental stability tests indicate that the aluminates with the Ba 3 CaAl 2 O 6 phase sintered in air as well as hydrogen is more environmentally stable than that with Ba 3 Al 2 O 6 phase sintered in CO 2 and O 2 mixture. The process of sintering 612 aluminate in CO 2 and O 2 mixture is beneficial for superior emissivity on the condition of avoiding exposure to moisture. [ABSTRACT FROM AUTHOR]

In order to optimize the synthesis process of barium-calcium-aluminate (BCA) for the application of impregnated dispenser cathodes, the influence of two precipitants, ammonium carbonate (AC) and ammonium hydrogen carbonate (AHC), on the chemical composition, phase transformation, thermal behaviors and morphology of the precursors was systematically investigated by means of XRD, TG-DSC, FESEM, and EDS mapping analysis. The results revealed that AC precipitant facilities to form NH 4 Al (OH) 2 CO 3 (AACH) phase and barium calcium carbonate in the precursor, while the product precipitated by AHC comprises amorphous γ -AlOOH phase and the carbonate. Both precursors precipitated by the AC and AHC undergo various stages of phase transformations and finally converted to an emission-active material Ba 3 CaAl 2 O 7 phase after sintering at 1200 °C. DC emission current values have been measured and the maximum space charge limited current densities are 8.0 ± 0.3 and 6.5 ± 0.4 A/cm2 at 1130 °C b for the testing cathodes impregnated with the AC and AHC precursor aluminates, respectively. The difference in the emission capacity originates from the barium content in the aluminates prepared with different precipitants. [ABSTRACT FROM AUTHOR]