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Diffusion pumps are great mechanisms for creating a high-vacuum environment between 10−10 to 10−2 mbar for industrial purposes. The great thing about diffusion pumps is there are no moving parts. The only thing moving when the pump is in operation is the flow of the diffusion pump oil between liquid and gaseous states. This flow is controlled by the temperature used to heat the oil; that is, the higher the temperature, the faster the diffusion pump oil will evaporate resulting in higher and faster vacuum pressure. By the way, if you’re new to diffusion pumps, see how diffusion pumps work. Logically speaking, to achieve the highest vacuum at the quickest speeds, you should set the temperature to as high as possible. Before doing so, here are some considerations you should look into:

  1. A diffusion pump already operates in very rugged conditions such as high heat and pressure, to increase temperatures while maintaining stability, make sure to use high quality diffusion pump oil.
  2. Make sure to use only high quality o-rings and sealing material. Be prepared to monitor these as they may require change more frequently.
  3. It takes longer to reach higher temperatures.
  4. Be ready for higher energy costs.
  5. Lastly, make sure you have a high quality diffusion pump.

From the considerations listed above, it is evident that increasing temperature of diffusion pump oil will result in higher overall cost. Therefore, the key to operating a diffusion pump at the highest efficiency requires controlling temperature to balance between the required vacuum rate and cost. Based on experience, we have actually come up with a chart to guide you through the most efficient temperature settings based on your required vacuum pressure and type of diffusion pump oil used.

Required Vacuum Pressure Diffusion Pump Oil Used Recommended Temperature
10-5 to 10-6 Torr 702 180-190 °C
10-7 to 10-8 Torr 704 220-230 °C
10-9 to 10-10 Torr 705 245-255 °C



The steam inside of a diffusion pump needs to go straight to a back pump, and should never be discharged into the atmosphere.