Design and Fabrication of UHV Chambers: Best Practices and Pitfalls on the Road to Ultra-high Vacuum.l（特高压腔室的设计与制造：通往超高真空的最佳实践与陷阱。）
What is the impact of material selection, surface finish, and design execution in ultra-high vacuum? What pumping power is actually needed for the application? And why can it be difficult to achieve good ultimate pressure?
（超高真空中材料选择、表面光洁度和设计执行有什么影响?实际应用需要多大的泵送功率?而为什么能很难达到好的极限压？）
Ultra-high vacuum (UHV) by definition begins at an absolute pressure of 10-7 mbar, which means that surface outgassing becomes critical to ultimate pressure at this pressure range. The flow in the UHV is molecular, the mean free path length is more than 1 km. If the pressure continues to drop to 10-12 mbar, the free path length grows to 10,000 km. The remaining particles left in the vacuum chamber now experience interactions only with the vessel walls, but not, or almost not, with each other. In this range, the materials and the surfaces of the chamber become massively more important. So what do you need to consider when designing, manufacturing and operating chambers and components for this pressure range?
（超高真空( UHV )根据定义,从 10 - 7 mbar 的绝对压力开始,这意味着在这个压力范围内,表面出气对最终压力至关重要。特高压中的流是分子流，平均自由程长度大于 1 km 。如果气压继续下降到 10 - 12 毫巴，自由程的长度会增长到 10 , 000 公里。留在真空室中的剩余粒子现在只与容器壁发生相互作用，而不是或几乎不是相互作用。在这个范围内，腔室的材料和表面变得非常重要。因此,在设计、制造和操作此压力范围的腔体和组件时,您需要考虑什么?）
UHV chamber（特高压室）
Criteria for material selection（材料选择标准）
As a start, you need high gas tightness for the chamber wall, as well as low intrinsic vapor pressure and low content of foreign gases. If this cannot be avoided, the material should at least outgas rapidly so that any troublesome residual gases can be pumped out quickly. In UHV, the chamber volume is not an important factor, at most it acts as a buffer during the pressure rise after the pump is switched off or pushed off. In this case, the residual gases come from the surfaces and volume of the vessel walls or installations.
（首先,您需要腔室壁具有高气密性,以及低本征蒸汽压和低杂质气体含量。如果这种情况无法避免，那么材料至少应该迅速排气，以便任何棘手的残余气体都可以迅速排出。在特高压中，腔室容积不是一个重要的因素，最多只是在泵关闭或推掉后的压力上升过程中起到缓冲作用。在这种情况下,残余气体来自容器壁或设备的表面和体积。）
Strength and corrosion resistance are further criteria. Since the sealing surfaces must not deform at a pressure difference of 1 bar, a sufficiently strong material is required.（强度和耐腐蚀性是进一步的标准。由于密封面不能在 1 bar 的压差下变形,因此需要足够坚固的材料。）
Corrosion resistance must also be ensured under difficult conditions such as bakeout in atmosphere or with chemically active process gases. It is therefore important to test the materials for their resistance. Good stability during temperature changes and adapted expansion behavior are needed to ensure that the chamber is and remains tight. Materials for flanges and gaskets must be matched.
（在困难的条件下,如在大气中烘烤或使用化学活性工艺气体时,也必须确保耐腐蚀性。因此，测试这些材料的电阻是很重要的。需要在温度变化期间保持良好的稳定性和适应的膨胀行为,以确保腔室保持紧密。法兰和垫片的材料必须匹配。）
Stainless steel and copper have similar coefficients of thermal expansion and are therefore a good combination. Stainless steel and aluminum are only a limited match because after temperatures of over 150 °C, the flange connections are often no longer tight when they cool down.
（不锈钢和铜有相似的热膨胀系数，因此是一种很好的组合。不锈钢和铝只是有限的匹配,因为温度超过 150 ° C 后,当它们冷却时,法兰连接往往不再紧密。）
Properties are followed by handling and availability of the materials, because they should be able to be processed with reasonable affordable effort, and must of course be available.
（属性之后是材料的处理和可用性，因为它们应该能够以合理的负担得起的努力进行处理，当然必须是可用的。）
Due to the low demand in UHV technology, there is no own material development and one has to work with what is already available. Austenitic stainless steel is particularly suitable for UHV applications.
（由于特高压技术的低需求,没有自己的材料开发,只能使用已有的材料。奥氏体不锈钢特别适用于超高压应用。）
Interactions between the surfaces of a vacuum chamber and the surrounding gas.（真空室表面与周围气体之间的相互作用。）
Effects in ultra-high vacuum（超高真空中的影响）
The following terms describe the effects that happen at surfaces in UHV:
1. Adsorption: Gas deposits on the surface of solids or liquids, such as particles sticking to the chamber wall.
2. Absorption: Gas trapped in solids or liquids. Absorption often follows adsorption. Particles previously attached only to the surface are now embedded in the chamber wall.
3. Desorption: Release of adsorbed gas into the environment. The particles retained by the first two effects detach from the chamber wall again.
4. Permeation: Transport of gas through a liquid or solid. Permeation = adsorption + diffusion + desorption.
Pressurization, adsorption and absorption are not problems because the particles are held and do not disturb the vacuum. Both effects happen on all surfaces that are in contact with atmosphere, as well with each ventilation. Desorption is the main opponent on the way to a good ultimate pressure. This is because particles attached to the outside of the chamber diffuse through the chamber wall during permeation, increasing desorption into the vacuum chamber.
（以下术语描述了发生在特高压表面的影响:
1.吸附：气体沉积在固体或液体表面，如粘附在腔壁上的颗粒。
2.吸收：困于固体或液体中的气体。吸附之后往往是吸收。以前只附着在表面的颗粒现在嵌入到室壁中。
3.解吸：将被吸附的气体释放到环境中。前两种效应所保留的颗粒再次从室壁分离。
4.渗透：气体通过液体或固体的传输。渗透=吸附+扩散+解吸。
加压、吸附和吸收都不是问题，因为粒子被保持住，不干扰真空。这两种影响发生在所有与大气接触的表面上，以及与每个通风。解吸是主要对手的方式一个良好的最终压力。这是因为附着在腔室外部的颗粒在渗透期间通过腔室壁扩散，增加进入真空腔室的解吸。）
Definition of working pressure（工作压力的定义）
Some basics about the requirements for the materials have now been described. Next, the desired working pressure pWork must be determined in order to proceed with the construction of a vacuum chamber.
（现在已经描述了有关材料要求的一些基本情况。接下来,必须确定所需的工作压力 pW or k ,以便继续建造真空室。）
The backing pump, up to a maximum of 10-3 mbar pumps out the volume after which a high or ultra-high vacuum pump with a suitable pumping capacity provides the working pressure. For this purpose, it is necessary to calculate or at least estimate the gas loads resulting from desorption, permeation, leakage and process gases.
（前级泵最大可达 10 - 3 mbar 泵出容积,之后由具有合适泵送能力的高真空或超高真空泵提供工作压力。为此，有必要计算或至少估计由解吸、渗透、泄漏和工艺气体引起的气体负荷。）
