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Recently, chalcogenides have attracted much attention as electrocatalysts in hydrogen evolution reaction (HER). However, few studies have been conducted on the electrocatalytic properties of gallium oxides and chalcogenides. In this paper, a Ga 2 XY (X ≠ Y, X, Y=O, S, Se, Te) defect structure doped by non-metal B, C, N, P, Si, and As have been designed. According to the study, the doping of non-metal atoms can significantly enhance their HER properties, the Ga 2 OSe-As Xi -Xi structure and Ga 2 SeTe-Si Xi -NM structure possess intensely excellent HER properties in this study with the Gibbs free energy of 0.01 eV and 0.00 eV, respectively. It is found that the Ga 2 SeTe structure has a more concentrated electron transfer range compared to the Ga 2 OSe structure, leading to a superior HER performance. This work provides a new idea for the study of HER electrocatalytic performance of the Ga 2 XY system, and it is expected to be applied to HER catalysts affordably and efficiently. • Screening of non-metal doped Ga 2 XY defective structures for HER electrocatalytic performance. • The introduction of Ga vacancies significantly enhances the HER performance of Ga 2 XY structures. • The Ga 2 SeTe defective doped structure has a more concentrated electron transfer range compared to the Ga 2 OSe structure. • The As-doped Ga 2 OSe structure and the Si-doped Ga 2 SeTe structure containing Ga defect have a near-zero ΔG H. [ABSTRACT FROM AUTHOR]

As the effect of factors like temperature and stress on the magnetic properties of electrical steel materials are gradually being emphasized, many research teams are carrying out related tests. Currently, most studies focus only on the effect of a single factor on the magnetic properties, while in reality, multiple factors exist simultaneously in electrical equipment. Therefore, accurate data of alternating (1D) and rotational (2D) magnetic properties under simultaneous loading of temperature and stress are very important. In this paper, a system based on a vertical rotational single sheet tester (VRSST) with temperature and stress loading parts is designed and constructed. Then, the 1D and 2D magnetic properties under many combinations of different temperatures, uniaxial and biaxial stress are measured and analyzed. [ABSTRACT FROM AUTHOR]

The high power pulse generators have been widely used in high power microwave generation and plasma physics research. In this paper, a novel compact solid-state high power pulse generator is studied, numerically and experimentally. The generator is mainly composed of the primary energy supply, the magnetic pulse compressor, the Blumlein type low-impedance pulse forming network, and the square waveform pulse transformer. Especially, design considerations for a solid-state high power pulse generator are proposed. Experimental results show that pulses with a peak power of 2 GW, a duration of 150 ns, and a repetitive rate of 10 Hz are continuously achieved on a dummy load. The dimension is Φ60 × 210 cm2, and the average power density reaches ∼5 W/L. Experimental results show reasonable agreement with numerical analysis. [ABSTRACT FROM AUTHOR]

A pulse forming network (PFN) is a significant component, contributing a lot to the overall dimension of pulse generators. In order to both reduce the size of PFN and improve the output waveform quality, this paper proposes a compact low-impedance PFN with a rotational symmetry structure. The PFN consists of four groups of Blumlein pulse forming units (PFUs) connected in parallel along the angular direction, and the spline curve structure is applied in each PFU, which achieves a higher space utilization rate. The theoretical maximum energy density of PFN is 6.6 J/L as the dimensions of PFN are φ500 × 138 mm. Field-circuit co-simulation is carried out based on the spatial model of PFN and the double switch modulation circuit to analyze the effects of switch delay time (time between main switch and steep discharge switch), as well as the output port position affecting the output pulse waveform. The results show that the PFN is appropriate to achieve quasi-square wave pulse modulation as the switch delay time is 290 ns with the output port positioned at the periphery. The verification experiments are also carried out. The results show that the PFN can generate a quasi-square wave pulse with an output voltage of 49.6 kV, a pulse width of 83 ns, and a peak power of 1 GW on a matched load. The output pulse exhibits a distinct flat top, with the fluctuation of the plateau being less than 3%. [ABSTRACT FROM AUTHOR]

A pulse transformer has advantages of compactness and long lifetime achievability, and is considered an important candidate for the development of high voltage pulse generators. In this paper, a fast rise time high voltage pulse transformer with a compact structure is studied numerically and experimentally. Specifically, the structure of the pulse transformer was designed with paralleled winding groups. The response and insulation characteristics of the pulse transformer are investigated numerically. After that, a fast rise time high voltage pulse transformer was built, and scaling experiments were performed to analyze the influence of the feed structure of the pulse transformer. Importantly, the pulse transformer was successfully used in a low impedance generator, and high voltage pulses with a peak voltage of about 260 kV, a pulse duration of 170 ns, and a rise time of 65 ns were achieved on a resistive load of 32 Ω. The ratio of the transformer is approximately 1:3. Experiments show reasonable agreement with the numerical analysis. [ABSTRACT FROM AUTHOR]

Solid-state pulsed power systems are characterized by high repeatability, high reliability, long lifetime, free maintenance, and easy usage. Such systems with moderate peak power (100-MW level) are widely applied in the high average power region; however, many issues are still to be researched to obtain GW-level peak power. In this paper, a high power solid-state pulse generator delivering a GW-level quasi-rectangle pulse is developed to investigate the electrical characteristics of the generator: 1) the system design is accomplished based on a reasonable setting of a power compression ratio combining semiconductor switches and magnetic switches and verified via circuit simulation; 2) key technologies such as serially connected thyristor switches, magnetic pulse compressor (MPC), Blumlein type low impedance pulse forming network (LIPFN), and induction voltage adder (IVA) are investigated for subsystem construction; and 3) at present, the experimental results achieved on a dummy load are a peak pulsed power of 5.2 GW, a pulsewidth of 170 ns, a repetitive rate of 20 Hz, and an operation time of 5 s with good waveform repeatability. The generator can be potentially applied for high power microwave (HPM) generation, X-ray sources, and industrial applications such as material surface treatment and pulse electric field (PEF) sterilization. [ABSTRACT FROM AUTHOR]

Amorphous magnetic core has been widely used in pulsed power technology with applications including plasma science research, high-power microwave generation, and material surface treatment. For different applications, dynamic properties of the magnetic core will vary with stimulated magnetic field which determines by magnetization time and waveform of the driving voltage. In this paper, toroidal amorphous magnetic core ($\Phi ~540$ – $740\times25$ mm) was investigated theoretically, numerically, and experimentally. Specifically, the circuit is analyzed. A high-voltage test stand, which can generate different driving voltages with same components, was designed and developed in our laboratory. Dynamic properties, including magnetic induction change, coercive force and losses, were studied under three different typical waveforms with the same magnetic flux. Driving voltages of the pulses were 12, 12, and 6 kV and the magnetization rates were 0.6, 1.2, and 0.6 T/ $\mu \text{s}$ , respectively. Experimental results show reasonable agreement with the numerical analysis. [ABSTRACT FROM AUTHOR]

Hydrogen as a sustainable and clean energy source has been widely noticed, but it is urgent to find an efficient and stable electrocatalyst to increase its hydrogen production. For the catalytic performance of electrocatalysts, defects, doping, and stress are usually selected to enhance the catalytic performance, on the basis of which in this paper, MSi 2 N 4 (M = Mo, W) system containing vacancies and bimetallic doping was constructed and analyzed for its HER performance. The results show that the formation energy of all structures is stable and Ni doping can significantly improve the stability according to formation energy of the structures with vacancy. Both ipsilateral doping and contralateral doping can significantly improve the Gibbs free energy of MA 2 Z 4 materials, especially the MoSi 2 N 4 doped with double Co. In particular, the values of Gibbs free energy of C-Ni-V N @MoSi 2 N 4 -N in and C-Co-V N @WSi 2 N 4 -N in are −0.027 eV and 0.041 eV, significantly better than the performance of the recognized electrocatalyst Pt, which has a free energy of only 0.09 eV. After doped with transition metallic atoms, the energy bands of all materials present semiconductor property. Our work provides a novel method for the regulation of MA 2 Z 4 family materials and a theoretical strategy for designing efficient HER electrocatalysts. • Screening of bimetal-doped MA 2 Z 4 with defective structures for HER catalytic activity. • The HER performance of the ipsilateral doping is better than that of the contralateral doping. • The vacancies can significantly improve the formation energy of Ni doped materials. • The MoSi 2 N 4 defect structure doped with double Co has a near-zero ΔG H. [ABSTRACT FROM AUTHOR]

Ferromagnetic core based magnetic switches are widely used in various pulsed power facilities. The dynamic characteristics of high-power magnetic switches, which have important impacts on the pulse modulation process, are analyzed via an improved numerical model in this paper. The model is established by simultaneously solving the circuit equations and the magnetic field diffusion equations. An implicit finite difference method is used in solving the diffusion equations, which has no numerical convergence problems, and the Jiles-Atherton model is used to obtain an accurate hysteresis loop of the core. The improved model predicts the performance of the magnetic switch quite well. It is then used to analyze the detailed dynamic saturation process of a core, and the core's saturation time predicted by the model is consistent with the experimental data, the error being less than 5%. Furthermore, the interlamination electric field is calculated and analyzed, and it is predicted that breakdown is most likely to occur at the inner side of the core and at the edge of the lamination. [ABSTRACT FROM AUTHOR]

Magnetic pulse compressors, based on magnetic switches, are considered as competitive candidates for high-voltage pulse generation. It is generally believed that the lack of operating-parameter tunability of these devices is currently one of the crucial factors limiting their applications. In this paper, an adjustable high-power magnetic pulse compressor, which is deemed as the key component of a power supply system, is investigated theoretically and experimentally. Dominant parameters of the compressor, including the compression ratio, the saturation time, and the peak voltage, can be regulated, which is beneficial for widening the application areas of power supply systems. Specifically, the prepulse of the magnetic pulse compressor is studied as one of the key parameters. A two-stage magnetic pulse compressor was then setup and when the charging time of the primary source was alternated between 19 and 25 μs, pulses with rise-time of 1 μs were achieved with good repeatability. This in turn verified the tunable capacity of the device. When applied in a solid-state high-voltage pulse generator, the pulse compressor successfully enabled the generation of intense electron-beam with peak power over 5 GW, peak voltage of 380 kV, pulse width over 170 ns, and repetitive rate of 20 Hz. The device has been successfully used for research on plasma science and for driving the sources of high-power microwaves where the requirements on the device often vary substantially. In the latter application, based on the high reliability of the solid-state pulse generator, optical diagnosis has been conducted of the plasma expansion characteristics of the magnetically insulated coaxial diodes cathode, in order to analysis the mechanism of the pulse shortening phenomenon. Experimental results show reasonable agreements with the analyses. [ABSTRACT FROM AUTHOR]

In this paper, a compact solid-state high voltage pulse generator, composed of a pulse transformer and a magnetic pulse compressor, is investigated numerically and experimentally. The generator can achieve pulses with a peak voltage over several tens of kilovolts and a rise-time in the microsecond level, which can be widely used in plasma physics research, high power microwave generation, and material treatment. Specifically, PSpice software is used to analyze the performance of the generator. Then, the generator was constructed in our laboratory. The experimental results illustrate that when the charging voltage of the generator was changing from 10 kV to 14 kV, typical pulses with a peak voltage ranging from 67 kV to 95 kV and rise-time between 10 µs and 12 µs were obtained on a dummy load. The generator can continually work over 10 min with a repetitive rate of 20 Hz, and until now, it has been successfully achieving over 1 × 106 high voltage pulses. Experiments show reasonable agreement with numerical analysis. [ABSTRACT FROM AUTHOR]

Magnetic switches could improve the stability, reliability, repetition rate, and life of pulsed power systems, based on which, a high power, low impedance, and long pulse generator has been investigated numerically and experimentally. The generator accomplishes the power compression and the pulse forming at a relatively low voltage level, consisting of a core-type pulse transformer, a two-stage magnetic compression unit, a low impedance pulse forming network, and magnetic type main switches. A full circuit model was developed using PSPICE software to analyze key factors that influence output characteristics of the generator. Key subsystems were manufactured and experimental research was carried out on the whole system. Preliminary results achieved with a dummy load of 2.5 $\Omega$ show that the output pulse power is about 2.0 GW and the pulsewidth is about 170 ns, which are in reasonable agreement with the numerical analysis. [ABSTRACT FROM PUBLISHER]

A compact repetitive high-power pulse generator, which could be used for high voltage applications including high power microwave and low temperature plasma, is described. Stray resistances which influence the performance of the generator were discussed and numerically optimized. Then, the high-power pulse generator was built in our laboratory. Experimental results show that pulses with peak power of 30 MW, peak voltage of 87.6 kV, and rise time of 60 μs, approximately, were obtained on a capacitive load of 200 nF. The repetitive rate was 10 Hz and the generator has successfully worked for over 10 000 shots for high voltage applications. [ABSTRACT FROM AUTHOR]

Pulsed power generators utilizing magnetic switch technology within the 100 ns scale have become widespread for surface treatment, high power microwave generation, and food processing, in which the dynamic characteristics of the magnetic switch perform an important function. The saturation process, electric field between layers, and energy loss are closely associated with the applied time scale of the magnetic core, which affects the dynamic characteristics of the switch. However, compared with the study within the microsecond scale, the dynamic characteristics of magnetic switches within the 100 ns scale have not been studied in depth. In this paper, the dynamic characteristics of a coaxial magnetic switch modulating pulse forming networks (PFNs) are studied via both field-loop co-simulation and scaled experimental test. It is found that increasing PFN section number (Ns) leads to an acceleration in the saturation process of the core, which helps understand the switch performance of the magnetic core more clearly. With respect to a specific magnetic switch based on a ferromagnetic core, it is quantitatively analyzed that increasing Ns from 1 to 10 leads to a 16.1% reduction in core saturation time (tsat), a 13.4% increase in eddy loss (EET), and a 5.7% rise in maximum interlamination field strength (Emax) under the 100 ns scale; however, tsat is reduced by 19.3%, EET increases by 5.2%, and Emax rises by 2.3% under the microsecond scale. The results could provide a design reference for magnetic switches in pulsed power generators. [ABSTRACT FROM AUTHOR]

Given the elevated expense and constrained accessibility of platinum, the primary catalyst employed in electrocatalytic hydrogen evolution, it becomes essential to pinpoint an alternative catalyst demonstrating exceptional catalytic efficacy and broader scalability potential. In this study, we undertook an exhaustive inquiry into the electrocatalytic activity concerning hydrogen evolution of the monolayer Janus MoXTe (where X represents S and Se) utilizing first-principle calculation. Furthermore, an evaluation of the performance of defective MoXTe structures was conducted. Our findings illuminate that the incorporation of non-metallic elements like B, C, N, and P into MoXTe can be employed to finely adjust the Gibbs free energy (ΔG H) to approximately 0 eV. Particularly, the doping of B and P into the 1T phase of MoSTe (1T-MoSTe-B@ represents 1T phase of MoSTe-B@ and 1T-MoSTe-P@ represents 1T phase of MoSTe-P@), the doping of P into the 1T′ phase of MoSTe (1T′ phase of MoSTe-P@), and the doping of P into the 1T′ phase of MoSeTe (1T′ phase of MoSeTe-P@) exhibit ΔG H values that are in close proximity to zero (ΔG H = 0.02, −0.03, 0.06, and −0.14 eV, respectively). Through further analysis, we found that the pristine and defective structures all exhibit metallic properties. And the doping of P improved HER performance more effectively among four nonmetallic dopants. In details, H get 0.21, 0.29, 0.43 and 0.28 e on doping of B and P into 1T phase MoSTe (1T phase of MoSTe-B@ and 1T phase of MoSTe-P@) and the doping of P into 1T′ phase MoSeTe (1T' phase of MoSeTe-P@). This study provides strategies for the design of MoXTe monolayer electrocatalysts, and it is expected to be applied to HER catalysts in affordable and efficient manner. • Screening of Catalytic Activity of 1T, and 1T′ phases Janus MoXTe (X = S, Se) monolayers. • Nonmetallic atom doping can affect the interaction between H and the material surface. • The doping of B and P into the 1T phase of MoSTe, P into the 1T′ phase of MoSTe and MoSeTe can improve the conductivity. [ABSTRACT FROM AUTHOR]

Amorphous alloys are widely used as the core material for motors and transformers, which are subjected to stresses during manufacturing and operation processes. For instance, the compressive stress can influence the magnetic properties of amorphous alloys which leads to local overheating in the device and reduce the reliability. A high-frequency magnetizer with a stress application unit is designed and constructed to investigate the magnetic properties of amorphous alloys up to kilohertz range under stress conditions. The amorphous alloy sheets will fracture under stress because of their poor ductility and brittleness, so this paper uses laminated amorphous alloy sheets as the sample. The hysteresis loops and loss characteristics of amorphous alloys under stress ranging from 20 MPa tensile stress to 20 MPa compressive stress at a frequency of 50 Hz to 4 kHz are investigated. This research can provide data support for the design of cores in electromagnetic devices. [ABSTRACT FROM AUTHOR]

This paper puts forward a novel high-voltage pulse generator, which can output a near square waveform across the load. The generator is composed of a conventional Marx generator, an $LC$ filter and a metal–oxide varistor (MOV) in parallel with the load. The Marx generator and the filter form a two-section type-A Guillemin pulse forming network (PFN). The PFN outputs a near square waveform and the MOV further stabilizes the voltage because of the MOV’s nonlinear resistivity. Circuit simulation verifies the working principle. Design parameters for the conventional PFN are derived. Considering the stray inductance of the filter, a more realistic PFN circuit is proposed and its parameters are derived. Preliminary experiments are conducted and verify the concept. Typical output waveforms have 20–30-ns rise time, 1000–1100-ns pulsewidth, and ~7-kV peak voltage. The pulse generator based on this concept is suitable to be used as a compact, long-pulse high power microwave modulator as it has a simple design, a well-defined flat top and it can output near constant voltage even if the load’s impedance varies. [ABSTRACT FROM AUTHOR]

The generation of annular relativistic electron beams (AREBs) with a good uniformity and longitudinal consistency needs intensive investigations, especially when no guiding magnetic field is supplied. Without a guiding magnetic field, ring-shaped cathodes with a width of several millimeters were utilized to generate AREB instead of knife-edged cathodes because of the space-charge force. Results of the fast framing optical photograph experiments and high power microwave (HPM) experiments show that the quarter-circular shielding electrode can improve the uniformity of the AREB obviously, and the carbon fiber cathode is validated to be an appropriate choice, which showed better emission characteristics and better performance in generating HPM than the graphite cathode and the polymer velvet cathode. [ABSTRACT FROM AUTHOR]

In recent years, the pulse forming technology based on metal oxide varistors (MOVs) has been verified to be an effective way to generate high-voltage quasi-square pulses. Due to the limited varistor voltage of a single MOV brick, multiple MOV bricks connected in series are required to stabilize a pulse with high amplitude (larger than hundreds of kV), which leads to the rise of the series inductance of the MOV branch and the flat-top droop in the output waveform. This paper provides two solutions to reduce the influence of the MOV branch inductance on output waveforms. One is that a coaxial evolute structure of the MOV bricks connected in series is designed, which can not only improve the insulation capacity but also reduce the branch inductance. Another is that a flat-top compensation scheme named "PFN-MOV" (Pulse Forming Network) is proposed, which adds an LC filtering branch to shape the signal into a flat-top rising wave with ripple and then offsets the flat-top droop caused by the inductance of the MOV branch. Based on the above ideas, a high-voltage, long-pulse width, flat-top compensation pulse generator is designed and tested, and a quasi-square pulse with voltage amplitude of more than 500 kV, pulse width greater than 800 ns, rise time of less than 50 ns, and flat top of about 600 ns is obtained experimentally. This MOV based generator has the advantage of simple design, compact construction, and better flat top, which is promising to be used as a compact long-pulse driver in many fields, such as high-current accelerator, industrial dedusting, medical sterilization, and cancer treatment. [ABSTRACT FROM AUTHOR]

In this article, a self-breakdown repetitive gap switch based on the graphite electrodes with surface modified by TiC is investigated to improve the scattering of the breakdown voltage. The self-breakdown repetitive gap switch was experimentally studied with the graphite electrodes and two kinds of TiC modified graphite electrodes (hereinafter referred to as TiC-I electrodes and TiC-II electrodes). Results show that the scatterings of the breakdown voltages of the graphite, TiC-I and TiC-II electrodes were 2.49%, 1.80%, and 1.54%, respectively. Compared with the graphite electrodes, the mass losses of TiC-I and TiC-II electrodes are reduced by 50% and 68%. The influence of electrode surface morphology on the switch stability is analyzed based on the mechanism of switch conduction process. Compared with the graphite electrodes, the electric field amplification coefficients of TiC-I and TiC-II electrodes are more evenly distributed, which leads to the more evenly distributed field emission current density. Thus, the breakdown areas of TiC-I and TiC-II electrodes are smaller and the gas breakdown processes are more stable than those of the graphite electrodes, resulting in smaller scattering of the breakdown voltage. The method that decreases the scattering of the breakdown voltage and reduces the mass loss of the electrodes by modifying graphite electrodes surface can greatly improve the stability of the switch, which is of significance to the application of the switch in the compact, long time stable operation of high-power pulse power devices. [ABSTRACT FROM AUTHOR]

Most high-power gyrotrons are driven by the thermal cathodes, and the output power can only reach megawatt (MW) level. In the present study, a single anode explosive emission cathode (EEC) magnetron injection gun (MIG) with the high beam current, the pitch radio of 1.2 and the controlled beam velocity spread was designed. At the peak voltage of 300 kV, the peak beam current of 1.1 kA and pulsewidth of 170 ns were emitted by a carbon fiber array (CFA) emitter. Compared to the reported EEC MIG, large beam loss was avoided in this experiment. The guiding center radius of 14.1 mm was close to the simulation results. CFA has the stronger emission capability, the lower emission threshold electric field, and the better emission uniformity than sharpened edge graphite (SEG), so it is suggested as the emitter of the EEC MIG. [ABSTRACT FROM AUTHOR]

A pulse forming network (PFN) has the advantages of compactness and long pulse achievability, which could meet the requirements of military and industrial applications of pulsed power technology well. In this paper, a compact low impedance Blumlein-type PFN based on ceramic capacitors is investigated numerically and experimentally. Generally, in order to increase the compactness of the PFN, an angular distribution and an axially parallel connected structure with a theoretical peak energy density of up to 5.8 J/L are employed. The dimensions of the PFN are Φ 560 × 345 mm2. A sharpening switch, which can efficiently reduce rise-time of the output pulses, is utilized to improve the performance of the PFN. The compact low impedance Blumlein-type PFN was assembled in our laboratory. The results of low voltage experiments show that the PFN could generate quasi-square pulses with an output power of 50 MW and a peak voltage of approximately 13.2 kV on a matched dummy load. Impedance and output pulse duration of the PFN are 3 Ω and 135 ns, respectively. The results of high voltage experiments show that pulses with a power of about 1 GW and an energy density of about 2.5 J/L were obtained. Experiments show reasonable agreement with numerical analysis. [ABSTRACT FROM AUTHOR]

The pulse forming network (PFN) has the advantages of compactness and long-pulse achievability, and is widely used in military and industrial applications. In this paper, a novel Blumlein-type PFN is investigated numerically and experimentally. Specifically, the device is composed of five Blumlein-type PFN units, which are parallelly connected in the axial direction, and the LC elements of each unit are distributed in the angular direction. Dimensions of the PFN are only Φ 560 × 345 mm2 due to the novel compact structure. Small volume is necessary in military and industrial applications, especially for some mobile platforms. Electromagnetic coupling in the structure is theoretically analyzed to improve the performance of the device. Importantly, the impedance of the structure is only 1.5 Ω, which can efficiently reduce insulation difficulty at the same power level. In order to improve the performance of the PFN, a sharpening switch is added in the circuit. Simulation results show that a 170 ns quasi-square pulse is obtained on a 1.5 Ω dummy load, and the jitter of the flap-top is only about 2%. The PFN is built and preliminarily studied in our laboratory. Quasi-square pulses with a peak voltage of 3.1 kV are obtained on a water load of 2.1 Ω. The jitter of the flap-top is ∼3.9%. Experimental results show reasonable agreement with numerical analysis. [ABSTRACT FROM AUTHOR]

In 100-MW level relativistic gyrotrons driven by explosive emission cathodes (EECs), significant parasitic oscillations are caused by the high beam current and the large beam velocity spread. In this study, the parasitic oscillations in an X -band coaxial relativistic intense current gyrotron were explored. The oscillations were suppressed in particle-in-cell (PIC) simulations through modifications of design. Lossy ceramics were inserted to suppress the parasitic modes in the beam tunnel. The beam collector was optimized to keep the electron beam from the cyclotron resonance region of the parasitic modes. In the 3-D PIC simulation of the whole tube, the output power of 35 MW and efficiency of 20.6% were achieved under the voltage of 300 kV, the beam current of 567 A, the pitch factor of 1.24, and the velocity spread of 25.6%. A single TE01 mode operation was achieved in this relativistic coaxial gyrotron. [ABSTRACT FROM AUTHOR]

The pulsed power technology has been applied to many defense and industrial fields. Different applications have different demands on the parameters of the pulsed power systems. However, the parameters of the current pulsed power systems are usually fixed and cannot be changed easily. As a special nonlinear device, metal-oxide varistor was considered to be applied for generating square pulses. Moreover, the magnetic switches are widely used in the field of the pulsed power technology due to the special switching characteristic. This paper proposed a high voltage pulse generator with pulse width adjustable based on the magnetic switch and metal-oxide varistor. The pulse forming network and metal-oxide varistor were combined to generate quasi-square pulses, the magnetic switch was used as a crowbar switch to sharpen the falling edge and the pulse width was adjusted by changing the reset current. The paper carried on theoretical analysis as well as simulation study, and developed preliminary experiment based on the simulation results. In the preliminary experiment, the falling edge of the voltage waveforms obtained on a dummy water load is less than 50 ns, the flat-top is about 7 kV and the pulse width is adjustable within 200 ns-900 ns. This kind of pulse generator with pulse width adjustable can be applied to many fields such as corona plasma generation, industrial dedusting and medical disinfection. [ABSTRACT FROM AUTHOR]

Unlike planar diodes, separate research of the axial and radial plasma expansion velocities is difficult for magnetically insulated coaxial diodes. Time-resolved electrical diagnostic which is based on the voltage-ampere characteristics has been employed to study the temporal evolution of the axial and radial cathode plasma expansion velocities in a long pulsed magnetically insulated coaxial diode. Different from a planar diode with a “U” shaped profile of temporal velocity evolution, the temporal evolution trend of the axial expansion velocity is proved to be a “V” shaped profile. Apart from the suppression on the radial expansion velocity, the strong magnetic field is also conducive to slowing down the axial expansion velocity. Compared with the ordinary graphite cathode, the carbon velvet and graphite composite cathode showed superior characteristics as judged by the low plasma expansion velocity and long-term electrical stability as a promising result for applications where long-pulsed and reliable operation at high power is required. [ABSTRACT FROM AUTHOR]

Abstract: Hollow magnetic microspheres with micro-mesoporous shells were constructed with layered cobalt-based ferrocenyl coordination polymers (Co-Fc-HCPS) through a one-step Ostwald ripening process. The diameters of microspheres and corresponding cavities were controlled in the range of several microns by tuning the reaction time and reactant concentration, which would attribute the microspheres with high loading, and enhanced mass diffusion and transfer efficiency. The high crystallinity of hollow microspheres allowed determination of the crystal structure of cobalt-based ferrocenyl coordination polymer, which crystallized in Brucite-type layered structure with the formula of Co4(OH)4(FcDC)2, (H2FcDC=1,1′-ferrocenedicarboxylic acid), by combination of powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), element analysis (EA), and Fourier transform infrared spectroscopy (FT-IR). N2 adsorption/desorption investigation revealed the existence of both mesopores around 3.81nm and micropores of ca. 1nm in the shells. The hollow microspheres exhibited spin-canted antiferromagnetism with weak ferromagnetic ordering below ∼52K, which showed a remanent magnetization (Mr) of 1.0 μ B and a large coercive field (Hc) of 5 kOe at 7K. [Copyright &y& Elsevier]

Abstract: Porous magnetic microspheres with large particle size (350–450μm) were prepared with sulfonated macroporous polydivinylbenzene as a template. The preparation process included ferrous ion exchange and following oxidation by hydrogen peroxide. The results showed that the weight fraction of magnetic nanoparticles exceeded 20wt% in microspheres after the preparation process was repeated three times. X-ray diffraction profiles indicated that the crystalline phase of as-formed magnetic nanoparticles was magnetite (Fe3O4). TEM images revealed rod-like magnetite crystal after the first oxidation cycle, however, the crystal morphologies were transferred into random shape after more oxidation cycles. The applicability of porous magnetic microspheres for removal of cationic dyes from water was also explored. The results exhibited that basic fuchsin and methyl violet could be quickly removed from water with high efficiency. More importantly, the magnetic microspheres could be easily regenerated and repeatedly employed for wastewater treatment. Therefore, a novel methodology was provided for fast removal cationic dyes from wastewater. [Copyright &y& Elsevier]