Diffusion pumps operate on a principle of inertia that states that objects at rest tend to stay at rest unless acted upon by another force. By heating up oil, a diffusion pump can force the larger oil molecules to change the inertia of air molecules inside of a vacuum chamber. By slamming these high-energy molecules into the air molecules, a diffusion pump is essentially capable of pushing air out of a chamber.
At the bottom of a diffusion pump is a heating element (around which sits the vacuum oil). Above the heating element is an umbrella, which guides the vaporized oil down towards the foreline (exhaust). Once the vaporized oil comes in contact with the edge of the diffusion pump, it condenses and falls back down towards the heating element to start the process over again.
In order to ensure that the diffusion pump remains cool enough to have this condensation occur, external cooling systems must be present. In our system, we use a liquid nitrogen cold trap and water baffle, along with an air-cooling system to preserve the stability of the temperature of our diffusion pump.
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