Greetings,
one of our rotary vane fore vacuum pumps (Pfeiffer Duo 5) on our Finnigan Delta S failed and it seems that oil vapor entered the vacuum tube connection from the fore vacuum to the turbo pump (the large one under the source). The backround scan showed lots of peaks. The complete vacuum tube system (from all three fore vacuum pumps) was disconnected and cleaned carefully. The large turbo pump under the source was dismounted and after putting it on the side, some oil seeped out of the pump. We cleaned the pump as good as possible, but I am not sure if this was enough. The fore vacuum pump was replaced. By the same time the source was opened since a leak was detected on the tube connecting the change over with the source. The gaskets were replaced.

After re-connecting everything and the reintegration of the source we pumped over the weekend an reached good vacuum (HV and FV, the FV took a while...). We checked for leaks with Argon but did not find something. We heated the source and the flight tube to 130 to 150 °C overnight (baking and a kind of heating wire wrapped around the source and flight tube).

The backround scan (slow magnet scan) this morning still showed lots of peaks which should not be there. We will check for a leak again, but I am concerned that the contamination with oil vapour (maybe into the source/tube itself?) is causing this.

Any suggestions on what we can do are highly appreciated.

Robert



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Robert van Geldern
GGA-Institut (Leibniz Institute for Applied Geosciences)
Stilleweg 2, D-30655 Hannover (Germany)
fon: +49 (0)511 643-2716 (fax: -3665)
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