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Reports until 21:47, Sunday 16 December 2012
robert.schofield@LIGO.ORG - posted 21:47, Sunday 16 December 2012 (4945)
PSL table vibration from chiller solved by removing quick-connects

The crystal chiller circuit has been increasing the motion of the PSL table by factors of 2 to 10 between 70 and 800 Hz (here). The vibration level varies in time and we have had some success by removing air from the manifold etc., but, until now, we have made no dramatic improvements.

In a recent alog (here) we showed that the quick-connect fittings in the high-flow crystal chiller circuit produced vibrations that were orders of magnitude larger than for barbed connector fittings, possibly because the nozzle in the quick-connects causes a small stream of water to spray chaotically and with high velocity inside the tube, and we suggested replacing the ones on the crystal box manifold.

Oliver Punken was here this week from UTB to work on PSL tasks, so we replaced quick-connects in 2 stages. In the first stage we replaced the connectors on the crystal box manifold, and straightened out the flow path (Figure 1). Figure 2 shows that the problem virtually went away after replacing these two connectors.  We also replaced the quick-connects and straightened out the flow in the manifold under the table (Figure 3) but made no further visible improvements (we were hoping to reduce the small residual at 100 and 150 Hz).

We may face future beam jitter problems from the chiller circuits, but the table vibration problem that we had identified is essentially solved. We recommend that LLO replace the two quick-connects on the manifold at the crystal box. They may also want to replace the two on the manifold under the table to keep both sites the same. 

Robert S., Michael R., Oliver P., Rick S.

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