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Message ID: 165     Entry time: Mon Nov 7 11:27:16 2016
Author: Gabriele 
Type: General 
Category: Vacuum 
Subject: Turbo pump excites some resonance at 58 Hz 

I looked into a couple of turbo pump switch on periods, and in both cases when the pump speed hits 58 Hz, a resonance is excited. I'm not sure what's resonating.

Today I let the roughing pump reduce the pressure to a level lower than usual, and this seems to mitigate the effect. The disk wasn't shaking as much as it did in previous pump-downs.

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