A vacuum chamber is a hard enclosure from which all the gases and air are discharge thanks to a vacuum pump.
Vacuum chambers are required to avoid contamination of samples in many disparate kinds of spectroscopy and for thin film depositions. Most vacuum chambers are fabricated in aluminum because it is nonmagnetic and so it allow to controll magnetic fields from outside the chamber.
Aluminum is a good choice also because compared to other types of metals, it absorbs minor water and trace gases.
UHV (Ultra high vacuum) means having pressures lower than about 10-13 atmosphere.
Vacuum chambers can be really useful: even at 10-10 atmosphere, it takes only 1 second to cover a surface with a contaminant.
For more info about it click here and read the wikipedia complete description.
Although there are several options available in the production of vacuum chambers, there are just a few materials that seem to be used over and over again. There are several reasons why these materials work the best and we’ll explore those reasons right now.
For high vacuum chambers, the material most commonly used is a high grade 300-series stainless steel. This metal has some great properties that make it perfect for use in a vacuum. First and foremost, the steel is mechanically strong. It is able to withstand incredible forces and very low pressures when it is used correctly. Another great property of the metal is that is weldable. Many models of vacuum chambers are sealed not only by o-rings, but by welded metal.
Another desirable property of 300-series stainless steel is that it has a magnetic permeability that is very close to 1. Which means that it will almost never interfere with any magnetic fields. Besides that, the metal has a very high resistance to atmospheric corrosion, which goes a long way when you’re worried about durability.
Sometimes, when researchers will be operating in the HV Torr range, perhaps for a large simulation chamber, they may choose to produce the chamber using a mild steel. This is most often done because it is a cost effective option when compared to 300-series steel such as 316L. However, there are several problems associated with mild steel. The first being that it does not have the desirable magnetic permeability of stainless steel. Besides that it does not carry the corrosion resistance or out-gassing properties.
If the researchers desire to control a magnetic force inside of the vacuum from outside of the chamber, different kinds of aluminum may be a good option.
If you are concerned with preventing external fields from entering a vacuum chamber, mu-metal is a good material.