CSRm Ultra-High Vacuum System

The new accelerator project （ HIRFL-CSR ） constructed at the Heavy Ion Research Facility in Lanzhou （HIRFL） is approaching completion. It is a multipurpose cooler-storage-ring system, consisting of a maim ring （CSRm）, an experimental ring （CSRe） and two transfer beam lines. The UHV system of CSRm is the most representative subsystem in the project. To minimize the beam loss due to charge exchange of the heavy ions with the residual gas molecules, the pressure of the CSRm vacuum system should reach 3.5 × 10^-9 Pa （N2 equivalent） and the pressure of 8 × 10^-10 Pa is expected for very heavy ion such as uranium to make its lifetime longer than 50 s in the ring. Now, the vacuum system of CSRm has been completed and a pressure less than 5 × 10^-10 Pa has been obtained. In this paper the layout of the CSRm vacuum system, the vacuum equipment in CSRm, the treatment method for the CSRm vacuum chambers, and the installation and operation of the system will be reported.

Design and Verification of an Auxiliary System for High Vacuum Die Casting

Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this research.The model has an aggregate unit consisted of ＂vacuum pump ＋ buffer tank＂ and a cylindrical container（including the shot sleeve,cavity and exhaust channel）.The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume models.An auxiliary system for high vacuum die casting is designed based on the above analysis.This system is composed of a vacuum control machine and a new vacuum stop valve.The machine has a human-computer control mode with ＂programmable logic controller（PLC） ＋ touch screen＂ and a real-time monitoring function of vacuum degree for buffer tank and die cavity.The vacuum stop valve with the ＂compressed gas ＋ piston rod ＋ labyrinth groove＂ structure can realize the function of whole-process vacuum venting.The new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly decreased.The systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.

High Quality SiGe Layer Deposited by a New Ultrahigh Vacuum Chemical Vapor Deposition System

An ultrahigh vacuum chemical vapor deposition (UHV/CVD) system is developed and the details of its construction and operation are reported. Using high purity SiH4 and GeH4 reactant gases, the Si0.82Ge0.18 layer is deposited at 550℃. With the measurements by double crystal X-ray diffraction (DCXRD), transmission electron microscopy (TEM) and Rutherford backscattering spectroscppy (RBS) techniques, it is shown that the crystalline quality of the SiGe layer is good, and the underlying SiGe/Si heterointerface is sharply defined.

Microstructure and mechanical properties of Mg-6Gd-3Y-0.5Zr alloy processed by high-vacuum die-casting

GW63K （Mg-6Gd-3Y-0.5Zr） magnesium alloys were prepared successfully by high-vacuum die-casting. Effects of fast shot speed and vacuum level on the grain size and mechanical properties of this alloy were studied. Microstructure of the alloys was analyzed by SEM, EDX and optical microscope （OM）. The effect of heat treatment on high vacuum die-casting （HVDC） GW63K alloy was also studied. The results indicate that with the increase of fast velocity, the tensile yield strength hardly changes, but the elongation first increases, then decreases. The optimum heat treatment process is solution treatment at 748 K for 2 h and aging at 473 K for 80 h. Under this condition, GW63K magnesium alloy exhibits a maximum tensile strength and elongation of 308 MPa and 9.45%. There is significant correlation between ductility and the presence of external solidified cells （ESCs）. The as-cast GW63K alloy consists ofα-Mg and Mg24（Gd,Y）5 particles. After heat treatment, Gd and Y atoms dissolve intoα-Mg matrix.

Simulation of α-Al grain formation in high vacuum die-casting Al-Si-Mg alloys with multi-component quantitative cellular automaton method

Al-Si-Mg alloys are the most commonly used material in high vacuum die-casting(HVDC),in which the morphology and distribution ofα-Al grains have important effect on mechanical properties.A multi-component quantitative cellular automaton(CA)model was developed to simulate the microstructure and microsegregation of HVDC Al-Si-Mg alloys with different Si contents(7%and 10%)and cooling rates during solidification.The grain number and average grain size with electron backscatter diffraction(EBSD)analysis were used to verify the simulation.The relationship between grain size and nucleation order as well as nuclei density was investigated and discussed.It is found that the growth of grains will be restrained in the location with higher nuclei density.The influence of composition and cooling rate on the solute transport reveals that for AlSi7Mg0.3 alloy the concentration of solute Mg in liquid is higher at the beginning of eutectic solidification.The comparison between simulation and experiment results shows that externally solidified crystals(ESCs)have a significant effect for samples with high cooling rate and narrow solidification interval.

Characterization of A390 aluminum alloy produced at different slow shot speeds using vacuum assisted high pressure die casting

The effects of vacuum assistance on the microstructure and mechanical properties of high pressure die cast A390alloy at different slow shot speeds were evaluated.Plate-shaped specimens of hypereutectic A390aluminum alloy were produced on a TOYO BD?350V5cold chamber die casting machine incorporated with a self-improved TOYO vacuum system.According to the results,the vacuum pressure inside the die cavity increased linearly with the increasing slow shot speed at the beginning of mold filling.Meanwhile,tensile properties of vacuum die castings were deteriorated by the porosity content.In addition,the average primary silicon size decreased from23to14μm when the slow shot speed increased from0.05to0.2m/s,which has a binary functional relationship with the slow shot speed.After heat treatment,microstructural morphologies revealed that needle-shaped and thin-flaked eutectic silicon particles became rounded while Al2Cu dissolved intoα(Al)matrix.Furthermore,the fractography revealed that the fracture mechanism has evolved from brittle transgranular fracture to a fracture mode with many dimples after heat treatment.

Best Magnetic Condition to Generate Hollow Cathode Glow Plasma in High Vacuum

Based on magnetron hollow cathode discharge, the magnetic condition of glow plasma generation in high vacuum, including both direction and magnitude of the applied mag- netic field, is theoretically derived and experimentally evaluated in this paper. Single particle orbital theory is introduced to discuss the possibilities to generate glow plasma at gas pressure under 10-2 Pa when the magnetic field direction is parallel or perpendicular or oblique to the electric field direction. A quantitative estimation criterion of magnetic induction intensity is also proposed in theory. The comparison with experiments suggests that glow plasma in high vacuum will form more easily in oblique magnetic field condition and that the criterion is accurate enough to estimate magnetic induction intensity at a certain gas pressure.

Study on Tribology Performance of Different Lubricant Additives under Atmospheric Pressure and High Vacuum Conditions

By using PAO-10 as the base oil, the tribological behavior of 11 additives under high vacuum condition was evaluated. By adopting some surface analytical instruments, such as scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS), the tribological mechanisms of these additives were studied. In air, O_2 can react with metal to form metal oxide that can protect the surfaces of rubbing pair during the tribological tests. According to the theory of the competitive adsorption, the function of some active elements is weakened. In a vacuum environment, the additives contributed more to the lubrication performance. The sulfur-containing additives could react with Fe to produce Fe Sx and "M—C" bonds("M" represents metal). They both had contributions to the lubrication. As for the phosphorus-containing additives, they only generated the phosphates during the tests. When the sulfur and phosphorus-containing additives were applied, the generated phosphates and Fe Sx had the primary contribution to the lubrication performance during the tests.

不锈钢管道的比放气率研究

不锈钢管道的比放气率是超高真空系统设计的关键参数,降低比放气率是提高真空度的有效方法之一。在西安200 MeV质子应用装置(XiPAF)的重离子升级工程中,重离子同步环真空管道内要求达到超高真空度(10−10 Pa量级),要求不锈钢管道的比放气率不超过1.5×10^(−13)Pa·m^(3)/(s·cm^(2))。文章通过研究降低不锈钢管道比放气率的方法,得到一套不锈钢管道处理方案,使得不锈钢管道的比放气率不大于此数值。降低比放气率的方案包括三个关键问题,即不锈钢材料的选取、真空炉高温烘烤方案选择和加热带烘烤方案选择。论文设计了实验方案,定制加工了四根相同尺寸的不锈钢实验管道,304和316L两种材料各两根,四根管道分为两组分别进行真空炉500℃和950℃烘烤,每根管道做四次加热带烘烤实验,烘烤温度依次设定为150℃、200℃、250℃和300℃,并测量每根管道最终的比放气率。为测量不锈钢实验管道的比放气率,搭建了一套比放气率测试平台。测量结果表明,加工厂家提供的304和316L两种不锈钢材料的初始管道比放气率的大小与材料种类无特定规律;实验中真空炉或者加热带的烘烤均能使比放气率降低1~2个数量级;管道依次进行真空炉950℃烘烤和加热带300℃烘烤之后,比放气率可以达到5×10^(−14)Pa·m^(3)/(s·cm^(2))以下,满足XiPAF重离子升级工程要求。

On the Cosmic Evolution of the Quantum Vacuum Using Two Variable G Models and Winterberg’s Thesis

We work within a Winterberg framework where space, i.e., the vacuum, consists of a two component superfluid/super-solid made up of a vast assembly (sea) of positive and negative mass Planck particles, called planckions. These material particles interact indirectly, and have very strong restoring forces keeping them a finite distance apart from each other within their respective species. Because of their mass compensating effect, the vacuum appears massless, charge-less, without pressure, net energy density or entropy. In addition, we consider two varying G models, where G, is Newton’s constant, and G-1, increases with an increase in cosmological time. We argue that there are at least two competing models for the quantum vacuum within such a framework. The first follows a strict extension of Winterberg’s model. This leads to nonsensible results, if G increases, going back in cosmological time, as the length scale inherent in such a model will not scale properly. The second model introduces a different length scale, which does scale properly, but keeps the mass of the Planck particle as, ± the Planck mass. Moreover we establish a connection between ordinary matter, dark matter, and dark energy, where all three mass densities within the Friedman equation must be interpreted as residual vacuum energies, which only surface, once aggregate matter has formed, at relatively low CMB temperatures. The symmetry of the vacuum will be shown to be broken, because of the different scaling laws, beginning with the formation of elementary particles. Much like waves on an ocean where positive and negative planckion mass densities effectively cancel each other out and form a zero vacuum energy density/zero vacuum pressure surface, these positive mass densities are very small perturbations (anomalies) about the mean. This greatly alleviates, i.e., minimizes the cosmological constant problem, a long standing problem associated with the vacuum.

可拆卸式深紫外光纤真空馈通结构

空间引力波探测中需要利用深紫外光的光电效应中和检验质量上积累的电荷,实现电荷管理。真空馈通是引入深紫外光纤的关键组件,须在实现电荷管理的同时确保惯性传感器真空度。文章提出了一种可拆卸的真空光纤馈通结构,通过金属套管的阶梯沉孔结构设计实现与深紫外裸光纤密封耦合,结合内螺钉压紧柔性材料获得金属套管与法兰的可拆卸密封。介绍了真空光纤馈通结构的设计与制作流程,通过氦质谱和光功率计测量了整体结构的泄漏率以及光传输损耗。实验结果表明,所设计的馈通组件的真空漏率小于1.0×10^(-12)Pa·m^(3)·s^(-1),传输深紫外光时的光功率损耗低于0.5 dB,能够满足地面和太空实验对电荷管理的需求,保障引力波探测正常进行。

高速纸机真空系统改造与节能实践

本研究以文化用纸生产线为例,对高速纸机真空系统进行改造,用磁悬浮透平真空泵替代水环式真空泵,对相应的工艺流程进行了优化,在确保纸机运行稳定的前提下,对高速纸机网部、压榨部真空分布及节能效果进行了分析。结果表明,经改造后纸机真空系统能耗降低30%,吨纸能耗下降21 kWh。

长沙至衡阳低真空管道磁浮线路方案动力性能评估

低温超高真空管磁悬浮是当前世界各国争相发展的超高速交通方式之一。目前,该研究正处于起步阶段,有必要对其动力性能进行评估。以长沙至衡阳低真空管道磁悬浮试验线为例,建立低温超导电动悬浮制式的车辆-线路耦合模型,分析磁浮车辆通过该段线路时的动力性能。首先,计算得到以1 000 km/h速度运行时的车体垂向和横向加速度、悬浮力及导向力情况。在此基础上,绘制各动力性能指标的频数直方图,分析其在不同区间的分布情况,研究各动力性能指标随曲线半径的变化规律。研究结果表明,磁浮车辆通过长沙至衡阳线路时,计算得到的车体垂向和横向加速度均低于舒适性限值,动力性能满足要求;从车辆动力性能角度来看,缓和曲线长度设置为1 400 m合理;曲线半径20 000 m、车速1 000 km/h与横坡为16°相匹配,各项动力性能指标较优。研究结果可为超高速磁悬浮线路设计提供参考建议。

抗高温保温筒相变材料仿真特性研究

随着以“慧磁”钻井中靶导向系统为代表的主动磁测技术的不断提升和应用范围的不断扩展,未来将更多应用在地热开发井、深部矿产资源勘探井等高温井中,高温会成为限制仪器在上述领域应用的“瓶颈”问题。为进一步提升“慧磁”系统的耐温性能,提出采用被动热管理方式,通过使用有限元方法对保温筒相变储热特性进行仿真计算,探究了吸热体最佳耦合长度并横向对比控温能力最佳的相变材料,分析了保温筒内部轴向温度和吸热体相态随时间变化情况。结果表明,上吸热体长度400 mm和下吸热体长度250 mm为最佳耦合长度,保温筒在150℃下工作6 h后,上吸热体相变潜热利用率96.7%,下吸热体相变潜热利用率70.5%,电路板最低温度63.48℃,低熔石蜡控温效果最佳。

The Wear Process of PTFE Coatings Under Vacuum Conditions

The wear process of PTFE coatings sliding against GCr15-bearing steel ball under vacuum conditions was investigated,and the hardness of the PTFE coatings on both sides of wear track was measured. The experimental results showed that the friction coefficient of the PTFE coatings increases with the increase of sliding distance under different sliding velocities. And the friction coefficient of the PTFE coatings increases with the increase of sliding distance under different sliding loads. The wear rate of PTFE coatings decreases with the increase of sliding distance. And the majority of the wear produced during the whole wear process of PTFE coatings sliding against GCr-15 steel ball comes from the early period of friction. The hardness of PTFE coatings on both sides of wear track increases as the distance increases and distributes symmetrically around the wear track. Scanning electron microscope( SEM) was utilized to investigate the worn surface of PTFE coating. It was found that the worn surface of PTFE coating is characterized by sever plastic deformation and spalling of the PTFE coating. The edge of wear track is characterized by micro cracking.

一种高压蓄能液压助力制动系统在商用车上的应用

为了摆脱车辆对真空源及真空度、气压等的限制,文章提出一种采用高压蓄能液压助力制动系统代替传统真空助力器;然后通过采用高压蓄能液压助力制动系统在某商用轻卡车辆进行制动选型的理论计算校核,替代原车真空助力器进行实车改制、调试匹配;最后进行制动性能对比测试。结果表明,该系统在制动性能及踏板感上均优于真空助力器,支持4.5t以上大吨位载重,通过该方案的理论分析与实车改制测试,结果符合预期,具备一定的工程应用价值。

低真空管道磁悬浮试验园区通信方案研究

低真空管道超高速磁悬浮列车具备高速、低能耗、低污染等特点,其应用将推动“超级城市群”的资源优化配置,提高人员及货物流动性,加速经济发展,实现清洁低碳、高效快速出行的新型交通运输方式。在试验线建设过程中,通信设计应满足试验园区智能化、数字化的统一管理需求,为园区提供安全防护、系统互通互联、实时监控等服务。本项目在试验控制中心设立数据中心,为园区各系统提供统一调度平台。

Manufacturing and High Heat Flux Testing of Brazed Flat-Type W/CuCrZr Plasma Facing Components

Water-cooled flat-type W/Cu Cr Zr plasma facing components with an interlayer of oxygen-free copper（OFC） have been developed by using vacuum brazing route.The OFC layer for the accommodation of thermal stresses was cast onto the surface of W at a temperature range of 1150oC-1200 oC in a vacuum furnace.The W/OFC cast tiles were vacuum brazed to a Cu Cr Zr heat sink at 940 oC using the silver-free filler material Cu Mn Si Cr.The microstructure,bonding strength,and high heat flux properties of the brazed W/Cu Cr Zr joint samples were investigated.The W/Cu joint exhibits an average tensile strength of 134 MPa,which is about the same strength as pure annealed copper.High heat flux tests were performed in the electron beam facility EMS-60.Experimental results indicated that the brazed W/Cu Cr Zr mock-up experienced screening tests of up to 15 MW/m^2 and cyclic tests of 9 MW/m^2 for 1000 cycles without visible damage.

HT7700透射电子显微镜的维护分析

阐述HT7700透射电子显微镜操作简单、分辨率高的特点,备受专业人士的关注。HT7700透射电子显微镜在日常应用过程中会受到环境、操作因素的影响,只有加强维护才能够充分发挥其作用。探讨利用文献资料法,对HT7700透射电子显微镜进行日常维护,包括真空系统、高压照明系统、成像系统、冷却循环水系统,从而降低显微镜出现故障的概率。

真空在高海拔模拟系统中的应用

高海拔环境中温度和气压的下降会对人体和设备产生一定影响,材料、器件、设备及生物体在高海拔环境下的性能和适应性可通过高海拔模拟系统进行测试。本文依托于成都XX风洞项目,通过罗茨真空泵对风洞进行海拔高度模拟,同时考虑温湿度的变化,设计了一套高海拔模拟系统,详细介绍了系统设计参数、组成、工作原理及操作流程。