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一、前言近年来,以半导体工业为主,超高压电子显微镜,加速器,表面物理研究等许多领域越来越需要清洁的超高真空。为达到这一目的,将注意力多集中在涡轮分子泵和低温泵方面。两者的优点是均比较容易获得清洁超高真空,而缺点是都需要烘烤出气,安装方向受到限制和需要辅助泵,要获得完全无油的超高真空排气系统似乎还存在一些问题。看来,一定需要清洁超高真空的装置的抽气,目前还是使用在上述方面问题较少,而且使用简便的离子泵。离子泵存在的问题是按容积计算泵的抽速小,特别是达到高真空后真空度越高抽速下降得越显著。抽速下降是因为气体压强在10~(-6)帕以上时电离空间的电子数几乎保持不变,而到更高真空时电子数随着气体压强的下降而减少。
I. Preface In recent years, the semiconductor industry has been the mainstay. In many fields such as EHV electron microscopes, accelerators and surface physics research, there is a growing need for clean ultra-high vacuum. To do this, focus more on turbopumps and cryogenic pumps. The advantages of both are that it is easier to get a clean, ultra-high vacuum with the drawbacks of requiring baking out of air, limited installation orientation, and the need for an auxiliary pump. There seems to be some problems with obtaining a completely oil-free, ultra-high vacuum exhaust system. It appears that the suction of a device that must be cleaned of ultrahigh vacuum is currently being used with a less problematic and simple to use ion pump. The problem with the ion pump is that the pumping speed of the pump is small according to the volume. In particular, the higher the degree of vacuum after the high vacuum is reached, the more significant the pumping speed drops. The pumping speed drops because the electron number in the ionization space remains almost constant at gas pressures above 10 -6 Pa, whereas at higher vacuum the electron number decreases as the gas pressure decreases.