The slowdown of a turbomolecular pump after power-off. Left alone in vacuum a large turbo can take 15 minutes or more to stop, and venting through a controlled vent valve at a set speed, often half of full speed, brakes the rotor with gas and shortens it. Spin-down time also serves as a health check, because worn bearings stop the rotor sooner than usual.
Shut the turbo off and let it spin down to 50 percent before the auto-vent kicks in.
Also heard as
- spin-down
- coast down
- run down
Related terms
Turbomolecular pump
High vacuum pump whose rotor blades spin at tens of thousands of rpm and bat molecules toward the exhaust.
At speed
Said of a turbo pump that has finished spinning up and reached its normal rotational speed.
Vent
To let gas back into an evacuated chamber, usually dry nitrogen, to bring it up to atmosphere.
Crash a turbo
To wreck a turbo pump's rotor by letting it hit the stator, most often by venting it hard while it spins.