In this paper, a low voltage non-magnetic ion pump based on pyroelectric materials is proposed, mainly applied in non-magnetic and high vacuum systems such as cold atom inertial sensors. By utilizing the discharge characteristics of pyroelectric materials in vacuum, the discharge current and high-voltage electric field required for the operation of ion pump can be obtained, eliminating the need to apply high voltage to the cathode like traditional ion pumps based on Penning source. The effectiveness of the pyroelectric ion pump is verified by activating it simultaneously with the molecular pump and only activating the ion pump in a 1000 cm3 stainless steel vacuum chamber. The working mechanism of the pyroelectric ion pump is proposed and experimentally verified.

Copper is the cooling transfer material used in cryogenic superconducting systems. Its effective thermal conductivity (ETC) in the 4 K region is only 400 W & sdot;m- 1 & sdot;K- 1, which leads to disadvantages such as large temperature differences and delayed temperature fluctuation. These restrict the improvement of the cooling performance of superconducting magnets. Oscillating heat pipe (OHP) has an ETC of two orders higher than copper, but it is unknown whether the heat generated by superconducting magnets excites OHP to produce oscillatory behavior. It limited its application in superconducting systems. In this study, the structure of helium-based OHP is designed, the heat transfer performance test rig in the 4 K region is constructed, and the numerical simulation method of the gas-liquid two-phase flow and heat transfer process of OHP is built. The oscillating power interval including the trigger power, the dryout power, the width of the power interval, and the optimal heating power is obtained with the heating power is 0.05 W - 1 W, the liquid filling ratio is 10 %-90 % and the turns is 1-6. And the change rule of oscillating power interval is revealed. The research results provide reliable data for the application of helium-based OHP in cryogenic superconducting systems.

In order to enhance the adsorption performance, a novel three-dimensional (3D) Ti-Zr-V thin film getter was developed by depositing Ti-Zr-V film on ZnO nanorod and nanotube arrays prepared through electrochemical deposition and chemical etching methods respectively. The composition, morphology, and adsorption performance of the 3D Ti-Zr-V thin film getter were investigated using energy dispersive spectroscopy, scanning electron microscopy, and hydrogen adsorption performance test. Compared with the two-dimensional planar Ti-Zr-V film, the 3D Ti-Zr-V film deposited on ZnO nanoarray exhibited significantly improved sorption rates (increased by 109.38% for ZnO nanorod array and 212.50% for ZnO nanotube array) as well as increased sorption capacities (enhanced by 89.93% for ZnO nanorod array and 174.82% for ZnO nanotube array). The enhanced adsorption performance can be attributed to both surface adsorption and gas diffusion in the nanoporous structures of the novel 3D Ti-Zr-V thin film getter.

Porous graphene membranes (PGMs) have nanopores with single atomic thickness, which enables the precise and stable supply of ultralow flow rate gas below 10(-14) Pam(3)s(-1). Different from a conventional channel, the surface diffusion (SD) process in PGM has become increasingly important and unique. However, the physical process and mathematical model of gas molecule transport in nanopores with single atomic thickness remain unclear. These inadequacies constrained the application of PGM in ultrasensitive leak detection. In this paper, the SD process in PGM was investigated using molecular dynamics simulation. A test rig was constructed to verify the simulation results. The nanopores in PGM were quantitatively characterized using a transmission electron microscope. Results show that a transfer region encircling the nanopores was identified, which plays a crucial role in the SD process. Furthermore, the physical model of SD process is described with a two-step model. Finally, a mathematical model of the SD process is established and validated. This paper provides nanoscale insights for an in-depth understanding of the SD process in PGM and promotes ultrasensitive leak detection technology.

In fusion devices, liquid lithium is increasingly employed as a plasma-facing material owing to high heat loads and neutron irradiation, as well as the necessity for impurity control in the plasma. Notably, addressing the retention of hydrogen and its isotopes deuterium and tritium is crucial for effective utilization of liquid lithium. To measure and control the hydrogen and deuterium content in liquid lithium, specialized permeation sensors and permeation extraction devices are essential. Consequently, there is a need for research on the permeation and diffusion of hydrogen in liquid lithium and permeable membranes. This paper introduces a model encompassing hydrogen adsorption, diffusion, and permeation in niobium membranes and liquid lithium. Experimental measurements of hydrogen adsorption in liquid lithium and hydrogen permeation in niobium membranes are presented. The scenarios are simulated using hydrogen transport module developed on COMSOL platform, resulting in a relatively good agreement with the experimental data.

In fusion devices, the actively cooled W-monoblocks of the PFUs (Plasma Facing Units) are installed in the divertor to protect the vacuum vessel and magnets against neutron flux in the bottom region of the vessel. Copper alloy is considered to be the ideal heat sink material due to its high thermal conductivity and sufficient mechanical strength, in which ODS (oxide dispersion-strengthened)-Cu is selected as a candidate. With the increasing of operating parameters, such as higher heat flux (-20 MW/m2, H-mode) and longer pulse (up to 2.00 h) in EU-DEMO [1], the heat sink structure will undergo thermal creep induced by high temperature, stress and long holding time, which accelerates fatigue failure and could potentially be a very critical issue for the long-term safe operation of the fusion reactor. In this paper, an ITER-like monoblock with ODS-Cu as heat sink was studied for its creep fatigue life under DEMO operation conditions. The temperature distribution and stress/strain results of ODS-Cu were determined using finite element analysis. The investigation shows that high temperature creep occurs at the heat sink. Based on a damage accumulation model, the predicted life of the PFUs for the divertor are investigated at different operating modes. The analysis provides theoretical feasibility for selecting ODS-Cu as a heat sink material. The effect of stress relaxation on creep behavior during thermal stress cycle was also demonstrated and this was compared with the same for CuCrZr.

BACKGROUND:As one of the primary residual gases in vacuum, hydrogen affects the performance of MEMS devices. It commonly uses a non-evaporable getter (NEG) to adsorb hydrogen in this case. One of the standard test methods for NEG is the constant pressure method. However, most constant pressure test systems control the intake flow by valves or small orifices. These methods are crude and limit the reliability of the result. Therefore, it is necessary to provide a stable intake flow method for the constant pressure test system to improve the accuracy of the test. RESULTS:We demonstrate a constant pressure system based on the microfluidic chip flowmeter to evaluate the hydrogen adsorption performance of non-evaporable getters in this paper. The microfluidic chip features microchannels with a height of around 100 nm. It is encapsulated with standard tube fittings, with leakage of less than 1 × 10-13 Pa ∙ m3∙ s-1. The conductance of the flowmeter is 10-12 m3∙ s-1, and the upper-pressure limit of the molecular flow is 105 Pa. It can control the intake flow of the adapted constant pressure test system from 10-11 to 10-7 Pa ∙ m3∙ s-1. Using this system, we tested the hydrogen adsorption capability of the Zr-Fe getter at different working pressures/temperatures and the types of gas it adsorbs were analysed. The results showed that the adsorbent has a noticeable adsorption effect on H2 and a partial adsorption effect on H2O, CO and CO2. SIGNIFICANCE:The microfluidic chip flowmeter can provide a stable intake molecular flow for the adapted constant pressure test system. It ensures the reliability of the measurement results. The ability of the flowmeter to offer tiny flow rates at 105 Pa can drastically simplify the test system and is more user-friendly for getters tests with poor adsorption performance. It has positive significance for industrial research on the non-evaporable getter.

A three-dimensional mathematical model of the bottom-blown converter was established using the Eulerian-Eulerian model and population balance model（PBM） with taking into account bubble breakup and coalescence. First, the calculated local flow velocities using the CFD-PBM model were compared with the experimentally measured values, showing that the CFD-PBM model was accurate in predicting the flow field. Then, the multi-fluid volume of fluid（MFVOF） model was coupled with the CFD-PBM model to simulate the gas column length and the structure of the gas-liquid two-phase region. In comparison with the experimental results of the water model, it was proved that the PBM-MFVOF coupled model was more precise in the calculation of the two-phase region and the gas column length. The gas-liquid two-phase flow and the shape of the gas column at the nozzle of the converter were simulated and studied under different gas flow rates. The gas column length increased with the bottom-blown gas rates. When the bottom blowing flow rate was 20, 60, 100, 150, and 200 L/min, the length of the gas column with gas holdup higher than 50 % was 35.99, 52.75, 65.27, 75.16, and 81.07 mm respectively. Finally, the typical gas blowing and stirring process of the industrial converter was simulated, which proved the feasibility of this PBM-MFVOF coupled model for calculating the gas-liquid flow and the length of the gas column in the industrial converter.

In this paper, experimental and numerical studies are conducted on supersonic molecular beam injection (SMBI) for fusion devices based on steady-state assumption. To explore the characteristics of SMBI from continuous to rarefied flow, the flow information is predicted by solving the Navier-Stokes (NS) equation based CFD method and direct simulation Monte Carlo (DSMC) method. To verify the coupled NS-DSMC method, a flow measurement apparatus platform is designed and constructed. A moveable full-range vacuum gauge with Pitot probe in the vacuum chamber is employed to measure the spatial distribution of the beam pressure signal. The simulation results are converted into Pitot pressure, corrected for rarefaction effect and compared with the experimental data. It is observed that the experimental results are consistent with the simulation results. This study provides technical support for the accurate prediction of SMBI flow characteristics and optimization of the SMBI systems.

Contact electrification at liquid-solid interface has aroused many research interests. Some recent researches suggest that the formation of electric double layer may be dominated by the charge transfer from liquid-solid contact electrification, which challenges the traditional electric double layer models. However, how the liquid-solid contact electrification affects the electrical double layer is still lacking of atomic-level mechanism details. In this work, an atomic-level investigation on the effect of contact electrification on the liquid-solid electric double layer are performed via first-principles and molecular dynamics simulations. The results suggest that the liquid-solid contact electrification can influence the ions distribution in the solution, thus influencing the formation of electric double layer and can even reversing its polarity under specific surface charge density. The mechanism is that the contact charges on the solid surface can affect the adsorption energy of anion/cation at the liquid-solid interface. The conclusion of this work can provide a more comprehensive understanding of the effect of contact electrification to the electric double layer.

Thermal insulation performance and service life of vacuum insulation sandwiches depend significantly on the internal residual gas pressure. Degradation of the vacuum can lead to a dramatic increase in thermal conductivity, so the initial internal pressure should be kept as low as possible during fabrication. In this paper, the evacuation and outgassing of vacuum insulation sandwiches are studied by modeling and experimental methods. A modified pump-down model for vacuum insulation sandwiches, called the recombination-dissociation-limited model, is proposed based on diffusion, recombination, and dissociation. The results show that the recombination and the dissociation of hydrogen on the inner surface have a hysteresis effect on the evacuation process, which explains well that the pressure inside the device remains above the ultimate pressure of the vacuum system after packaging. The experimentally measured evolution of the pressure and outgassing rate in the vacuum insulation sandwiches agree well with the calculated results. The simulation analyses the effects of temperature, pump-out port size, and ultimate pressure on evacuation efficiency. It provides a theoretical basis for predicting the dynamic pressure evolution during high vacuum packaging and selecting effective parameters in the packaging process.

The narrow structure within the vacuum system usually results in a slow evacuation process. Additionally, the high outgassing rate caused by the large surface-to-volume ratio can prevent the vacuum level from meeting the performance requirements of the device. In this paper, the evacuation of the stainless steel parallel plates is established based on a two-dimensional equation combined with the outgassing theory of the recombination–dissociation-limited model. The relationship between the measured and intrinsic outgassing rates was investigated by varying the gap size, pump-out port size, and temperature. The results show that the internal pressure is nonuniformly distributed during the pump-down process, even reaching a quasiequilibrium state. This indicates that the widely used throughput method can make a difference in measuring outgassing rates. This provides a theoretical basis for testing intrinsic outgassing rates, calculating pressure distribution, and configuring pumps or getters in complex vacuum systems.

Abstract Many studies on carbon nanotubes (CNTs) have revealed that gas transport behaves differently at the nanoscale compared to the macroscale. While traditional gas transport models do not account for the effect of adsorption, as the adsorbed gases at the macroscopic level are relatively minor and can be ignored, the significant specific surface area of nanochannels leads to a significant increase in the proportion of adsorbed gases. Therefore, the impact of adsorption on gas transport must be taken into consideration. In this study, the diffusion and adsorption behaviors of different gas molecules inside CNTs of different diameters were simulated based on equilibrium molecular dynamic and Grand canonical Monte Carlo methods. The transport diffusion coefficients of gases were calculated using flux correlation functions, and the surface diffusion coefficients of gases were derived by combining with rarefied gas kinetics. The results show that the transport diffusion coefficients of gases in carbon nanotubes are several times or even one order of magnitude higher than those calculated by Knudsen's equation, and the surface diffusion of adsorbed molecules in carbon nanotubes is responsible for the rapid transport, and for the first time, the surface diffusion coefficient of different adsorbed gases in CNTs at different pressures and diameters is derived.

WS2 with different layers were prepared by liquid-phase cascade centrifugation and then applied to fabricate Ag/WS2/Cu memristors. The correlation between WS2 layers and band gap was studied and the influence of the change in WS2 band gap on the switching characteristics was analyzed. It is found that as the thickness and layer number of WS2 decrease, the band gap gradually increases. The Ag/WS2/Cu devices exhibit bipolar resistive switching behavior. The larger the band gap of WS2, the smaller the switching voltage and the larger the switching ratio of the corresponding memristors. The double logarithm I–V curves verify that the switching mechanism of the devices is the trap-controlled space charge limited current mechanism. In addition, the charge transfer process is further explained with the energy band diagram and the differential charge density of Ag/WS2/Cu. This work can lay a theoretical foundation for the design and optimization of the switching performance of transition metal dichalcogenides (TMDs) memristors.

The deposition of high-performance micro-sized ultra-thick silver films is a critical issue. Hollow cathode magnetron sputtering is one of the promising techniques for depositing ultra-thick silver films. A novel cylindrical “three-dimensional magnetron sputtering” (3-DMS) magnet pack presented here was developed based on a conventional hollow cathode magnet pack to deposit high-performance ultra-thick silver film at a high rate. A stable process condition at the average power of 4 kW is realized by the new cylindrical “3-DMS” magnet pack's 137.5 mm diameter targets and a specially designed cooling well. Comparison of deposition rates with different power supplies and at different average power levels are discussed. The behavior of electrons on the target surface in this magnetic field arrangement is investigated using COMSOL Multiphysics software. The composition, topography, mechanical properties and residual stress of the ultra-thick silver film deposited by different sputtering modes (DCMS, HIPIMS, and Pulsed DCMS) are also discussed.

An innovative method using constant conductance element to measure the deformation rate of flexible container was proposed based on the theoretical model of dynamic micro-flow detection. The measurement system of dynamic deformation rate was built by using the semi-flexible container encapsulated with polyimide film, and a constant conductance element was installed between the flexible container and the pressure stabilizing chamber to provide a constant micro-flow rate. The dynamic differential pressure variation between the inlet and the outlet of the constant conductance element was measured and then the deformation rate of flexible container could be obtained through the iterative calculation of the measured differential pressure change over time. The results show that the deformation rate gradually decreases with the increase of differential pressure. In addition, Boyle's law was used to verify the experimental results of dynamic micro-flow detection method, and it is revealed that the measurement error is less than 11%. Finally, a standard leak element was applied to simulate the leak source of flexible container. The conductance of standard leak element and the leak rate of flexible container have been successfully predicted by using the measured deformation rate.

In order to break through the structural limitation of 2D planar film and develop getter with large specific surface area (SSA), the 3D Ni-nanoarray based Ti-Zr-V film getter was prepared to effectively increase the SSA and finally improve its adsorption performance. The morphology and adsorption performance of Ti-Zr-V films deposited on Ni-based nano-scaffold and silicon substrate were studied by scanning electron microscopy, thermogravimetric analysis and hydrogen adsorption test. The gettering properties are found to be directly dependent on the deposited thickness of Ti-Zr-V film. The results show that the 80-nm-thick Ti-Zr-V film can maintain the porous structure of the original Ni nanoarrays and has the largest adsorption rate (1.274 x 10(-2) mg/(s.g)) and adsorption capacity (0.0587 mg) in the thermogravimetric analysis experiment. Under the same preparation and activation conditions, the H-2 adsorption rate and adsorption capacity of 3D Ni-nanoarray based Ti-Zr-V film are about three times and twice that of Ti-Zr-V film on silicon substrate, respectively. This is because the increase in SSA promotes the gas adsorption on the getter surface. The study indicates that the application of porous nanoarray as scaffold for getter film is an effective way to improve the adsorption performance.

In this work, a new leak element based on transfer-free single-layer graphene was developed. The single-layer graphene was synthesized on Cu foil and small holes of about 10 mu m were drilled on Cu foil to reveal graphene membrane. The conductance of He, N2 and Ar through the graphene leak element was measured based on the difference method. The results imply that various gases exhibit molecular flow regime under pressures ranging from vacuum up to 105 Pa, and the conductance of the transfer-free graphene is about two orders of magnitude smaller than that of the wet-transferred graphene. The difference of conductance may result from the generation of micron-sized cracks and tears on graphene surface during wet-transfer process. The transfer-free single-layer graphene developed in this work is an excellent material for low-permeation leak element.

The nanofluidic chips with channels of 100-nm depth and 3-mu m width were employed as molecular flow standard leak elements for vacuum technology applications in this paper. The nanofluidic chips are fabricated by MEMS technologies while the macro-micro connection is achieved using glass fusion bonding and standard Swagelok (R) Fitting. It is found that the choice of annealing temperature and holding time is a key issue regarding fusion bonding and the optimal processing parameters are 780 degrees C, 5 min. Meanwhile, the sealing reliability of fusion bonding and the fitting connection is evaluated. Experiment shows that the flow conductance of the as-fabricated leak can reach 10(-13) m(3).s(-1) magnitude for He, N-2 and Ar. This standard leak has the advantages of controlled dimensions, reliable connection, and constant flow conductance over a range of 10(5) Pa.

Ag/tungsten disulfide (WS2)–polyvinylpyrrolidone (PVP)/Cu memristors based on monolayer WS2 nanosheets and polyvinylpyrrolidone (PVP) nanocomposites were fabricated, and the influence of PVP content on the switching behaviors was investigated. The results indicate that the WS2–PVP based memristors show write-once read-many times (WORM) memory behavior. Remarkable resistive switching results such as a low operating voltage (VSET < 1 V), a high switching ratio (>103), good endurance (>100 cycles), and data retention time (>200 s) are obtained. With the increase in the PVP content, the device VSET gradually increases, and the switching ratio first slightly increases and then remarkably decreases. The double logarithm I–V curves verify that the switching mechanism of the devices is the trap-controlled space charge limited current mechanism, which is explained with the energy band diagram.