For high and ultra-high vacuum, the two main choices are the turbomolecular pump and the diffusion pump. Turbo pumps are clean, controllable and oil-free but are precision machines; diffusion pumps are robust, low-cost and have no moving parts but rely on a heated working fluid. Both need a backing pump.
How each works
A turbomolecular pump uses high-speed bladed rotors to drive gas molecules towards the exhaust. A diffusion pump uses a heated oil vapour jet to drag molecules downward – no moving parts. See our pump types guide.
Compared
| Turbomolecular | Diffusion | |
|---|---|---|
| Cleanliness | Oil-free, clean | Risk of fluid back-streaming |
| Control | Fast start/stop, controllable | Needs warm-up/cool-down |
| Moving parts | High-speed bearings | None |
| Cost | Higher | Lower, robust for large loads |
| Ultimate vacuum | To ~10-10 mbar | To ~10-9 mbar |
Which should you choose?
Choose a turbomolecular pump for clean, controllable high vacuum on instruments and R&D; choose a diffusion pump for robust, cost-effective high vacuum on larger coating and furnace loads. Both need a suitable backing pump.
Turbo or diffusion for your system?
Tell us your process, chamber and cleanliness needs and we’ll recommend the right high-vacuum pump. Email [email protected] or request a quote.
Frequently asked questions
What is the difference between a turbomolecular and a diffusion pump?
A turbomolecular pump uses high-speed rotors and is clean, oil-free and controllable; a diffusion pump uses a heated fluid vapour jet, has no moving parts and is robust and low-cost but can back-stream fluid. Both reach high vacuum with a backing pump.
Which reaches a deeper vacuum, turbo or diffusion?
Both reach high and ultra-high vacuum – turbomolecular pumps to around 10^-10 mbar and diffusion pumps to around 10^-9 mbar, each with a suitable backing pump.
Are diffusion pumps still used?
Yes. Diffusion pumps remain common on coating plant and furnaces where their robustness, low cost and lack of moving parts are valued, despite the rise of turbomolecular pumps.
Written by the Girovac technical team. Girovac Ltd has supplied and serviced industrial and laboratory vacuum equipment from its North Walsham workshop since 1983. Last updated: July 2026.