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At Niagara College I worked on several labs in our clean room, which housed two diffusion pump systems. These systems are both equipped with bell jars and thermal evaporation systems. Below is a schematic diagram of a typical diffusion pump system, with all the general components listed.

Schematic Diagram of a typical diffusion pump system
Source: Thin Film Technology, 1968

The first system used in labs was an old Edwards system, and was strictly used for aluminum coatings. This system features a quartz crystal monitor with a gauge that reads the oscillation of the quartz crystal. A picture of this system is shown below.

The Edwards Vacuum System; on the left is the bell jar with the diffusion & roughing pump underneath (with LN₂ cold trap & valves)
Source: http://technology.niagarac.on.ca/courses/phtn1432/VacuumSystem.html

While this system is good for depositing simple aluminum coatings to substrates, it lacks the vacuum (purity) and precesion of our second system. The second system, which is used for research and the more advanced labs (such as Dielectric Coatings). This system features an inficon thickness monitor, and can reach a much higher vacuum than the Edwards system above (~10^-6 to 10^-7 on a good day). Pictures of this system are shown below.

Labeled diagram of the Bendix Vacuum System
Source: http://technology.niagarac.on.ca/courses/phtn1432/VacuumSystem.html

View of inside the bell jar of the Bendix system; the four filament holders are shown with the shutter over filament #4, the substrate holder is shown at the top of the picture, which holds about 20 substrates to be deposited. The thickness monitor is located in the centre of the substrate holder.
Source: http://technology.niagarac.on.ca/courses/phtn1432/VacuumSystem.html

Image of underneath the Bendix system, labeled
Source: http://technology.niagarac.on.ca/courses/phtn1432/VacuumSystem.htm