jeffrey.bartlett@LIGO.ORG - posted 18:37, Monday 19 September 2016 - last comment - 05:10, Tuesday 20 September 2016(29813)
PSL Chiller Trends After Flow Adjustment
Took a 12 hours trend of the PSL Chiller vital signs after this mornings flow adjustment. The various pressures and flows changes in the manifold, chillers, AMP and PWRMETER are not out of the range of expectation. The change in the PWRMETERFLOW is a bit larger than the changes in the other parts. Will monitor this over the next few weeks to make sure all is well. The interesting result is the changes in the four head flows and temperatures. On heads 1 through 3 the flow was reduced by about 0.1 l/m. On HEAD1 the temperature remained constant. On HEAD2 and HEAD3 goes up by 0.1 degree. What is interesting about this is the change in temperature actually smooths out the variation of the high/low temperature range. Need to monitor to see if this is holds up over time. HEAD4 has always been the PSL poster child of different, and continues this trend. When the flow was first adjusted it took a relative large drop (0.2 l/m) and over the next three hours the flow recovers to within 0.02 l/m of its original value. The temperature at first goes up and then settles down to its normal value. Whereas on HEAD2 & HEAD3 the temperature goes up and smooths out the high/low fluctuations; on HEAD4 the temperature goes up, then down and then smooths out the high/low fluctuations. It should be noted these changes are actually relatively small. The Crystal Chiller flows around 22 l/m and the Diode Chiller flows around 32 l/m.
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Looking at Jeff's plot it looks like after a while all the head flow numbers came back almost exactly where they were before the work in the PSL... The plot shows the noise measured by the PSL accelerometer last Friday (blue, Sep 16) compared with today right after people left the PSL table (purple) and a couple of hours ago (cyan - by this time the flow rate came back pretty much were it was). Red is the reference from ER9 (July). Any chance we can lower the head flow and keep it low?
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Whilst in the enclosure the flow rates were adjusted to be as low as possible without tripping the flow rate watchdog. It's hard to predict, at least for me, where the eventual flow rates will settle out. We could increase the amount of water by-passed at the water manifold to reduce the flow rates further, which I would prefer to be done with the laser off, and then allow the flow rates to settle down for a long period of time (like half a day or so).