三元ZrCrV吸气化合物粉末的制备和表征

采用非自耗电弧熔炼法制备ZrCrV合金铸锭,经机械破碎和球磨获得三元ZrCrV吸气化合物粉末。通过光学显微镜、扫描电镜、透射电镜以及X射线衍射仪观察和分析粉末形貌、成分和物相结构。结果表明:将纯金属锆、铬和钒按化学计量比1:1:1混合,经电弧熔炼得到的ZrCrV铸块呈典型的枝晶形貌。铸块在1 200℃真空热处理10 h后经球磨制得的ZrCrV粉末是典型的面心立方C15型结构laves相,呈不规则形状,粒径10～150μm。粉末中三元ZrCrV相纯度约92.75%(质量分数),另有5.27%的ZrCr2和1.98%的ZrV2相,粉末结晶度>90%。     

非蒸散型薄膜吸气材料研究进展

非蒸散型吸气薄膜是大型超高真空系统设备维持超高真空的重要材料,近来又成为基于物联网应用的MEMS器件维持可靠性和长寿命的关键材料。本文综述了非蒸散型薄膜吸气剂的基本原理、材料体系和制备技术,介绍了国内外吸气薄膜的材料现状、结构与性能、多功能化的最新进展,讨论了增大比表面积、调控纳米级精细结构的调控、实现多功能化和提高沉积精度是未来吸气薄膜技术的发展趋势。     

Thermal Conductivities of Granular UO2 Compacts with/without Uranium Particles

The thermal conductivities of granular UO₂ compacts with and without uranium particles were measured to evaluate the thermal performance of vibro-packed granular MOX fuels containing metallic fine particle oxygen getters. The thermal conductivity of the compact with 10 wt% of uranium particles was higher than that of the compact without uranium particles. After heating beyond 1,408 K, the melting point of the uranium particles, the thermal conductivity increased further. The evaluation model for analyzing such phenomena was developed. The model predicted that once the UO₂ compact with uranium particles was exposed to a temperature beyond 1,408 K, the uranium particles should melt and provide interconnecting areas between the UO₂ granules and uranium particles, and between other uranium particles. The resulting increase of the thermal conductivity was reasonably expressed by the effect of necks in the compact on the heat conduction.     

Research on deposition rate of TiZrV/Pd film by DC magnetron sputtering method

An accelerator storage ring needs clean ultrahigh vacuum.A TiZrV non-evaporable getter (NEG) film deposited on interior walls of the chamber can realize distributed pumping,effective vacuum improvement and reduced longitudinal pressure gradient.But accumulation of pollutants such as N2 and O2 will decrease the adsorption ability of the NEG,leading to a reduction of NEG lifetime.Therefore,an NEG thin film coated with a layer of Pd,which has high diffusion rate and absorption ability for H2,can extend the service life of NEG and improve the pumping rate of H2 as well.In this paper,with argon as discharge gas,a magnetron sputtering method is adopted to prepare TiZrV-Pd films in a long straight pipe.By SEM measurement,deposition rates of TiZrV-Pd films are analyzed under different deposition parameters,such as magnetic field strength,gas flow rate,discharge current,discharge voltage and working pressure.By comparing the experimental results with the simulation results based on Sigmund's theory,the Pd deposition rate C can be estimated by the sputtered depth.     

ZrCoRE薄膜的结构调控与吸气性能研究

运用扫描电镜、扫描原子探针、X射线衍射仪和动态法分析了高硼硅玻璃表面改性对ZrCoRE薄膜结构和吸气性能的影响.结果表明,ZrCoRE薄膜的纳米组织受衬底表面的影响较大,其表面粗糙度和结构无序度随衬底粗糙度增加而增大:经300℃激活30 rmin后,Ⅰ-型薄膜(Ra=5 nm)吸气性能随时间下降较快,Ⅱ-型(Ra=7 nm)、Ⅲ-型(Ra=59nm)及Ⅳ-型薄膜(Ra=125 nm)的吸气速率依次增大并具有平稳的吸气平台,Ⅳ-型薄膜吸气性能最好.     

杜瓦激活对探测器芯片温度影响的理论与试验研究

杜瓦激活过程会引起探测器芯片温度过冲,导致芯片失效。通过仿真计算分析了吸气剂激活过程中产生的温度分布,研究了探测器芯片在杜瓦激活时温度升高过冲的主要传热途径,并提出了一种吸气剂挡板方案。试验结果表明,该方案可将激活过程中探测器芯片表面的最高温度由105℃降至85℃,解决了激活过程中探测器芯片的温度过冲问题。     

环境气氛对DEB吸氢性能的影响

考察了CO、O₂等杂质气体对DEB-Pd/C消氢剂吸氢性能的影响。实验结果表明,CO对DEB-Pd/C初期的吸氢性能影响较大,而O₂对DEB-Pd/C初期的吸氢性能影响较小。同时考察了贮存气氛及贮存时间对DEB-Pd/C吸氢性能的影响。实验结果表明,在氮气、空气环境下贮存1.5 a的消氢剂仍具有良好的消氢性能;当密闭体系中的氢含量为吸氢剂理论吸氢容量的50%时,仍能将氩、氢混合气中的残余氢量控制在10 ppm以下。室温、潮湿环境气氛下贫铀样品贮存气氛中的消氢实验结果也表明,DEB-Pd/C消氢剂能很好地控制密闭体系中的氢含量。     

TiZrV吸气剂薄膜吸气性能的研究

TiZrV合金在180℃下加热24 h即可激活,是迄今发现的激活温度最低的非蒸散型吸气剂,已在粒子加速器领域得到应用。采用直流磁控溅射法在不锈钢管道内壁获得了TiZrV薄膜,并研究了薄膜对CO和H2的吸气性能。在200℃下加热24 h后TiZrV对CO和H2的抽速分别为0.23和0.02 L.s-1.cm-2,吸气容量分别为6.8×10-5和6.6×10-2Pa.L.cm-2,且随着激活温度和时间的增加,吸气性能会有所提高。     

Surface area, pore size distribution and microstructure of vacuum getter

An effective getter is necessary in vacuum technology. In order to obtain the adsorption mechanism of the getter, its microstructure information must be studied. Surface area, pore size distribution and microstructure of vacuum getter were studied with XRD, SEM and N₂ adsorption technique.Vacuum getter is composed of the different proportions of PdO and Ag₂O. The crystalline size of 3^# vacuum getter that includes W₂AgO = 22% and W_PdO = 78% is the maximum among all the vacuum getters. SEM images showed that vacuum getters expose a large number of nanometer-size pores. The adsorption isotherms of the vacuum getters are typical of type Ⅳ, characteristic of mesoporous material, and a type H₂ hysteresis loop is observed. Langmuir model describes N₂ adsorption at low pressure region. At the medium pressure, N₂ adsorption can be modeled by BET model. The pore size distributions of the vacuum getters are calculated by applying BJH method to the adsorption branch of N₂ isotherms at 77 K. With percentage of Ag₂O elevation, Langmuir surface area, BET specific surface area, the adsorption capacity and the pore volume become larger. But the average pore diameter becomes smaller. However, above Ag₂O content of 22%, an inverse behavior is observed. 3^# vacuum getter has the highest surface area and pore volume among all the vacuum getters. The experimental results and related analysis can be adopted in the later design of the vacuum tank.     

The vacuum system of the Low Energy Ion Ring at CERN: Requirements, design, and challenges

For the heavy ion program at CERN's Large Hadron Collider, lead-lead collisions with a design luminosity of 10²⁷ cm⁻² s⁻¹ are foreseen. This will be achieved after an upgrade of the ion injector chain where the Low Energy Antiproton Ring (LEAR) is currently converted into a Low Energy Ion Ring (LEIR). Avalanche-like heavy-ion induced molecular desorption, first observed at LEAR and systematically studied at CERN's Heavy Ion Accelerator (LINAC 3), is the major challenge to achieve the required average dynamic pressure of about 4×10⁻¹² mbar in LEIR. The LEIR vacuum requirements, the technical design, the implementation of non-evaporable getter coatings and low-outgassing collimators, and the concept of ion-beam scrubbing are reviewed in this paper.