Multi-element vacuum arc plasma sources have found extensive applications in numerous fields due to their ability to simultaneously generate multiple elemental ions. This paper carried out experimental research on the discharge characteristics in a vacuum arc plasma source based on cathode-anode cooperative discharge, which can produce multiple elemental ions. In the experiment, tungsten was used as the cathode and aluminum as the anode. Both electrodes were rod-shaped with a diameter of 1 mm, and the interelectrode spacing is set to 1 mm. Experimental results indicated that a disc-shaped plasma cloud could be observed at 2 mu s in the interelectrode region caused by the collision and accumulation of plasmas derived from the cathode and anode. The multispectral thermal imaging was used to measure the spatiotemporal distribution of the anode surface temperature during the discharge process. The results showed that the temperature in some areas of the anode increased to the melting point in 1 mu s, leading to a high density of anode vapor. The area of the high-temperature region on the anode expanded with time. The interelectrode electron temperature was in the range of 1-2 eV, increasing from the cathode to the anode when the disc-shaped plasma cloud appeared. This was because the anode vapor could reduce the arc conductivity and consequently significantly increase the Joule heat. At the end of the article, the samples coated using the above-mentioned device are shown. The coating was relatively uniform with minimal droplet content. The vacuum arc plasma source proposed in this paper can be used to generate multi-element plasmas with the advantages of simple structure and controllable products.

It is difficult to balance the spatial resolution and measurement time of prompt gamma activation imaging (PGAI) when it is applied to low flux neutron sources. In this paper, a single pixel imaging method based on rotation modulation collimator(RMC) was proposed to measure the spatial distribution of cadmium in plate samples with low neutron flux. The skew-Hadamard Uniform Redundant Array(URA) was applied to the encoded mode. The RMC device prototype is determined based on the encoded mode, and the MLEM was used for the image reconstruction. The reconstruction performance of multi-nuclide gamma point sources was verified by reconstructing and evaluating the distribution of gamma point sources (Cs-137, Na-22 and Co-60), and the influence of multiple nuclides on the reconstruction results was analyzed. PGAI measurements on the distribution of a Cd-containing plate sample were carried out within the neutron yield range of 1.5(+/- 0.2) x 106 s-1. The results showed that the reconstruction results were in good agreement with the experimental expectations. The SNR of the reconstructed image is 26.0 dB, and the structural similarity is 0.757. It shows that the RMC prototype can be used in PGAI at low neutron flux, and has good performance of element distribution measurement in the scene of miniaturized neutron source such as D-T neutron generator.

The compact ion source is widely used in plasma thruster, film deposition, ion implantation and so on. A compact surface flashover ion source with titanium films deposited on alumina substrates as the electrodes has been fabricated in this paper. The ion sources were prepared by two different methods: magnetron sputtering combined with lithography and evaporation deposition. The discharge stability and lifetime of the ion sources by two kinds of preparation were studied. The results showed that the film of the ion source prepared by evaporation had better discharge stability and adhesion. Then the discharge characteristics of the ion source prepared by evaporation had been analyzed. The results showed that no matter how the arc current changes, the extraction efficiency of this flashover ion source is about 5%. And when the arc current is larger, the cathode spot will occasionally jump to a farther position, resulting in unstable discharge and the increase of discharge area, but has no obviously effect on ion ionization and recombination. The particles generated by discharge of the ion source are mainly titanium ions and a small number of aluminum ions. These provide support for further understanding of the physical mechanism of compact surface flashover ion sources.

The metallic droplets generated by high-voltage gas arc erosion on electrode surfaces are the key factors constraining the reliability and service life of gas-insulated switches. The process of cathode erosion evolution forming liquid metal jets is the critical link in understanding the generation of metal droplets. This study establishes a two-dimensional numerical model of spot erosion on the cathode under high-pressure arc conditions, aiming to investigate the evolution of spots under arc plasma interactions and analyze the generation mechanisms of metallic particles during electrode erosion in conjunction with the instability analysis of liquid metal flow. The model divides the near-cathode region structure into sheath and presheath layers. By comprehensively considering the effects of multiple particle flows, the current density distribution of spots can be obtained through coupled solutions by establishing an electron energy balance equation in the presheath layer. The simulation results indicate that under the pressure gradient, liquid metal moves from the spot center toward the crater edges, forming wrinkles on the crater walls. A small amount of liquid metal splatters away from the electrode surface. The instability analysis of liquid metal flow reveals that the process of jet formation and droplet breakup in the erosion crater of spots is predominantly associated with Rayleigh-Plateau instability, with corresponding analysis conducted on the time required for this instability to develop.

Electrode erosion is an inevitable mass loss and morphology modification behavior of electrode materials under the action of arc plasma, which is one of the main factors that restricts the reliability and long-term operation efficiency of high-power pulsed devices. The interaction between arc and material plays a key role, especially in the adjacent zone of the electrodes. This work established a numerical model of diffused arc erosion in an atmosphere spark channel and tried to understand how arc plasma results in crater formation and mass loss of electrode material. The model mainly included metal vapor, electron, and background gas, which applied energy flux, pressure on anode, and ion, thermo-field electron are involved at the cathode surface. The electrode material experienced heating, melting, expanding, and finally formed an erosion crater or melting pool. In a diffused spark arc with peak current of 1 kA, current density, energy flux, and pressure at the electrode surface rise sharply in the initial 100 ns, with peak reaching 1E9 A/m(2), 1E11 W/m(2), and -10 MPa. And subsequently, they all descend quickly and oscillate with the spark current. The results show that the gas ion bombardment plays a dominant role in electrode erosion of atmosphere spark, instead of that played by thermo-field electron in vacuum arc. In two oscillating periods of spark current (about 4 mu s), the peak surface electric field at Mo and Cu electrodes could reach 1.1E9 and 1.5E9 V/m, which are slightly below that in the vacuum arc spot. Despite the obvious difference between Mo and Cu material characteristics, the peak temperature that could reach in the atmosphere spark arc is proximate, about 3100 K, far beyond the melting point. Evolution of the melting pool on Mo and Cu electrodes is discussed and crater characteristics are analyzed and confirm the erosion morphology with previous experimental results.

Accurate temperature measurement is pivotal in manufacturing, industrial modernization, and scientific research. This study proposes a multi-spectral thermometry method based on the gray body hypothesis and color temperature difference. The methodology involves selecting a target pixel and any other pixel and measuring their gray value with a multi-spectral thermometer. For an n-channel thermometer, 2n equations can be derived from Wien's displacement law. Subtracting these equations yields additional n equations, forming a system of 3n equations. These equations are solved via least squares fitting to determine the color temperature and gray body emissivity of both pixels. By establishing the relationship between gray body emissivity and channel-specific emissivity under the gray body approximation, the variance between theoretical and measured emissivity is calculated. The target pixel is combined with other pixels for calculation, and the resulting variances are compared. The temperature and emissivity of the target pixel are determined when the variance is minimized. If the variance meets the measurement error requirements, the corresponding result is regarded as the true temperature. This approach reduces the required number of spectral channels, circumvents overcomplicated emissivity models induced by wide spectral ranges, and enhances measurement accuracy (error <1%) while improving experimental efficiency. The method's validity is demonstrated through gas discharge temperature measurements, with results cross-verified against rotational temperature data, confirming its applicability in practical scenarios.

Many ion sources need to work in the order of 10(-3)-1-Pa pressure, so the influence of these pressures on ion extraction characteristics has been attracted attention. In this article, based on 2-D space and 3-D velocity (2D3V) particle-in-cell-coupled Monte Carlo collision (PIC-MCC) method, a simplified simulation model of argon ion extraction process under an extraction voltage of -10 kV is established. The influence of argon pressure on the density and velocity of electrons and ions is obtained. Then, the reason why the extracted ion current decreases obviously when the argon pressure increases to 1 Pa is explained. That is, the probability of elastic collision and charge exchange between argon ions and argon atoms increases obviously, which leads to the deceleration and divergence of argon ion beam. This provides support for further understanding of ion extraction characteristics and influencing factors.

In this paper, a three-dimensional model is used to describe the formation, development and proliferation of cathode spots in vacuum arc. The model includes hydrodynamic equations and heat transfer equations. The energy flux density, current density and pressure are taken as input parameters. The simulation parameters used in this model are derived from experiments and other research work. The initial position of the multiplication spots is randomly generated. The simulation results show that after the formation of a single spot, the metal droplets are completely formed and splashed evenly on the surface of the electrode, laying the foundation for the generation of new spots. The proliferation process of new spots will squeeze each other with the initial spots, forming multiple liquid metal ridges. The width and depth of new spots are related to the center temperature of the craters when they are produced, and they continue to expand under continuous energy flow injection, resulting in more complicated and serious ablation of the surface of planar electrodes. The simulation results are compared with those of other metals, and the position of new spots is controlled in the simulation. The simulation results show that the ablation on tungsten-copper alloy is less than that on pure copper metal cathode, but greater than that on pure tungsten metal cathode.

The extraction characteristics of multi-charged ions produced by ion sources are important for some useful applications. In this paper, the extraction process of Cu + , Cu 2+ , Cu 3+ and Cu 4+ mixed ions is simulated by setting ideal physical parameters in a two-dimensional Particle-In-Cell (PIC) code, and the evolution characteristics of density and velocity distributions of different charged ions during plasma (density about 10 15 m -3 ) motion and extraction are presented. Besides, the effects of grid thickness and grid aperture on the motion behavior of different charged ions and the extracted ion current are analyzed. The results showed that the ion diffusion increases with the increase of the ion charge, and higher charged ions are more likely to be affected by the grid. This provides support for further understanding of the extraction characteristics of multi-charged mixed ion beams.

Compact ion sources are widely used in plasma thrusters, thin film deposition, ion implantation, and so on. This study fabricated a compact surface flashover ion source with titanium thin films deposited on alumina substrates as electrodes. The fabrication process, phase composition analysis, ion current and ion current distribution, and mass-to-charge composition of the compact surface flashover ion source are presented in this article. The phase composition analysis revealed that the phase composition of the electrodes was not affected after more than 200 discharges; however, the discharge changed the diffraction peak intensity ratio. A parallel-plate electrode and 9-tip probe array were used to measure the total ion current and ion current distribution. The experimental results confirm the excellent discharge stability of the ion source, and the uniformity of the ion current at different positions. By measuring the mass-to-charge composition, it was found that the main composition of ions was Ti $^{\text{i}+}$ . In the initial discharge period, the dominant ion species were Ti $^{{\text{3}+}}$ and Ti $^{{\text{4}+}}$ . At a later period, the dominant ion species were Ti $^{{\text{1}+}}$ and Ti $^{{\text{2}+}}$ . The results can be useful in the development of novel compact ion sources.

Lunar water ice is an important resource to support the construction of lunar base and other deep space activities, and it is crucial to detect lunar water ice. In this paper, we studied the detection of lunar water ice based on a small neutron generator through Monte-Carlo simulation. The schematic of the detection system and the principle are explained. The simulation results demonstrate that the change of thermal neutron flux with the increase of water content is most obvious and clear. There is a positive correlation between thermal neutron counting and water content in lunar soil. Using thermal neutron counting, the water content can be obtained by inversion.

The characteristics of laser-produced metal hydride plasmas have been investigated in this work. The charge state and velocity of ions were determined by employing a time-of-flight technique in conjunction with an electrostatic deflection method. The ion velocities were found to be supersonic with values in the range of 104 to 105 m/s. The proportion of hydrogen ions was found to be lower than that of titanium ions. The ion emission behavior was studied by using a Faraday cup. When the total integrated space was taken into account, the ns pulsed laser was capable of producing hydrogen ion currents greater than one hundred mA. In order to understand the plasma generation process, we performed a comparative analysis between laser-generated plasma and arc plasma, and also investigated the effect of laser power density on the composition and velocity of the ions, the ablation properties of metal hydrides, and the maintainability of hydrogen ion emission.

The spatial distributions of different kinds of ions are usually not completely the same in the process of extracting. In order to study the reason for the different characteristics of ion extraction, a simplified simulation model of Cu+ and Cr+ ions extraction process was established by 2D3V (two-dimensional in space and three-dimensional in velocity space) particle-in-cell (PIC) method. The effects of different extraction voltages from 0 V to 500 V on the density distribution of Cu+ and Cr+ ions and the change of plasma emission surface were analyzed. On the basis of this model, the ion density distribution characteristics of Cu+ ions mixed with Li+, Mg+, K+, Fe+, Y+, Ag+, Xe+, Au+, and Pb+ ions respectively under 200-V extraction voltage are further simulated, and it is revealed that the atomic mass of the ions is the key reason for different ion density distributions when different kinds of ions are mixed and extracted, which provides support for further understanding of ion extraction characteristics.

The development and improvement of instrument 14 diagnosis of high energy ion generated by the method such as vaccum discharge is very important for improving the research level of high energy plasma. In this work , a time-of-flight mass spectrometer ( TOF-MS ) for diagnosis of high-energy ion was developed , and , the qualitative analysis of high energy ions (H+, H2+, C2+, Al3+, C+, Al2+, O+ and Al+) between 10 and 150 keV was carried out on the basis of aluminum vacuum discharge ion source. The influence of pulse width and voltage of ion gate on performance of TOF-MS was optimized, and it was found that, when the pulse width was 100 ns and the accelerating voltages were 20 kV and 50 kV , respectively , the best voltages of ion gate were +/- 500 V and +/- 2500 V. Besides , it was fk)und that the mass resolution was 22 FWHM ( Full width at half maximum) when the accelerating voltage was 50 kV. Temporal variation of intensity of different ions was further studied by changing the delay time of pulse of ion gate.

The deuterium plasma parameters of a miniature Penning discharge ion source have been measured by a single probe. Electron temperature and electron density can be acquired from the I-V curves. The results show that electron temperature increases and electron density decreases with the probe tip departing from the centre of plasma area. Meanwhile, both electron temperature and electron density increase with increase in discharge current. Electron temperature is about 1.8 similar to 7.1 eV and electron density is about 2.7 x 10(14) similar to 3.7 x 10(15) m(-3), when the distance between the probe tip and the centre of plasma area varies from 1 to 6 mm. Electron temperature is about 5.7 similar to 12.5 eV and electron density is about 6.7 x 10(14) similar to 2.2 x 10(15) m(-3), when discharge current varies from 50 to 200 mu A. The results can provide useful information for the design and operation of Penning ion sources.

以低气压条件下的铁电体离子发射特性为研究对象,通过结合高速相机、光谱的光学诊断和二维网格质点法耦合蒙特卡洛碰撞模型(PIC-MCC)的仿真模拟获得了锆钛酸铅(PZT)铁电体离子发射的主要成分、表面放电的发光及等离子体演化过程、离子的产生及离子电流形成机制,为进一步研究铁电体离子源奠定了基础.

Usually multicomponent ions are generated from cathodic vacuum arc plasma with compound cathodes. In this paper, a novel method to produce multicomponent ions by simultaneous anodic and cathodic vacuum arc plasmas with pure electrodes has been studied. The vacuum arc discharge has been operated with Al anode and W cathode. To characterize the plasma plume generation, a combination of high-speed camera and time-of-flight mass spectrometer has been used to measure the spot phenomenon and multicomponent ions, respectively. Luminous spots have been simultaneously found on the anode and cathode to produce multicomponent ions, which has been verified by the examination of electrode erosion using SEM. The ion charge state distribution and multicomponent ions have also been measured. For comparison, the characteristic of vacuum arc discharge operated with the exchange of electrodes has been studied, which exhibits obvious discrepancies. This behavior of vacuum arc is considered to be controlled by the difference of cohesive energy, because the heat flow to the electrodes is sufficient to evaporate the electrode, and the ionization process by the plasma occurs in the nonequilibrium layers near the evaporated surface in cathode and anode regions. This interesting result is proposed to use for the synthesis of compound films.

Dense plasma jet near cathode spot region was investigated by a Mach-Zehnder interferometer with high spatial ( 0.2 μm per pixel) and temporal (9 ns) resolution. The discharge was initiated between two needle-type electrodes. Four electrode materials including Cu, Ag, Sn and graphite were used simultaneously as both electrodes. Nanosecond interferometry yielded spatial-temporal plasma density distributions in the arc phase. Measurements of three metal cathodes showed the similar interferometric data, which were reported previously as the spot fragments connected with the cathode surface. However, four dense particle blocks were recorded for the graphite cathode. Two blocks contained the spot fragments connected with the cathode surface and the plasma balls separated from surface, but two dense gas balls contained the one connected with and the one separated from surface. The maximum electron density for four electrode materials showed a weak dependence on melting temperature but similar tendency as the freezing value occured in the Saha freezing model. The interferogram revealed the small localized dense density blocks and the maximum electron density expanding from Cu spots decreased slower than a quadratic drop in density. Above results confirmed that the explosive emission mechanisms of spot operation were dominant in plasma generation mechanism for metal electrode, but the thermal evaporation and droplets were the main sources of plasma for graphite cathode.

Measuring the pressure inside the compact sealed electronic vacuum devices is a difficult proposition that typically requires destructive analysis. In the paper, we offer an indirectly method to pressure measurement without operating the devices. Towards that end, a simple and compact Penning-type diacharge structure only include two electrodes and an additional permanent magnet is established. The discharge characteristics under different anode voltages and different pressures are studied. The principle in measuring the pressure inside compact sealed electronic vacuum devices is analyzed, and the pressure-current chart is acquired. A sustaining discharge strikes with a measurable pressure varying current starting at a pressure of 1-10 -2 Pa of helium. These results demonstrate the validity of this research and by applying our structure to compact sealed electronic vacuum devices, pressures inside the tubes can be measured without puncturing the vacuum envelope.

基于三探针方法开展了脉冲放电等离子体特性研究,实现了单次脉冲放电等离子体参数的时变特性诊断.采用金属罩屏蔽、示波器锂电池供电等方法降低了电磁信号干扰,利用Labview编制了特定的程序进行三探针诊断数据处理.根据脉冲放电等离子体具有多电荷态离子成分、离子超声速运动等特点,对三探针理论进行相应修正.诊断结果表明,整个放电脉冲内高压引出界面电子温度Te处于2～4 eV之间,离子密度ni处于1017～1018 m-3量级之间,与Langmuir单探针诊断结果吻合.