An Overview of Vacuum Science and Technology

In this book I have intentionally avoided equations whenever possible. The reason is simple Most people do not need, or use, equations when using equipment. Despite that, this introductory section on vacuum technology contains equations. They are presented so the reader may better understand the relationship between the various forces in vacuum systems. None are derived, and none are used beyond presenting some basic points. If you are interested in the derivation of any formula, see the recommended books at the end of this chapter. 

It is not necessary to know the material in this introductory section to run a vacuum system. However, it does explain terms and ideas that are used throughout the rest of this chapter. Because of the basic information contained within, I recommend that you read this section. 

The goal in creating a vacuum is to get rid of, or bind up, a significant amount of the gases and vapors (mostly air and water vapor) within a vacuum system. Regardless of the approach, the goal is a net reduction of pressure in the system. 

Aside from earthbound technological approaches to achieve a vacuum, the further away from the earth s surface you go, the less atmosphere there is and therefore the greater the vacuum (relative to atmospheric pressure on the earth s surface) that can be achieved. In fact, on earth, someone standing on top of Mt. McKinley experiences vacuum greater than can be created with a standard vacuum cleaner at sea level.1 Table 7.1 shows the approximate miles above earth to obtain various conditions of vacuum. As this table shows, outer space offers wonderful opportunities to produce vacuum conditions for experimental or industrial 

Pressure (torr) Quality of Vacuum Miles Above Earth (= miles) of Particles (per m 3) Mean Free Path (m) 

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