Robert, Tyler, Richard, Eric, TJ

Several years ago we were unable to lock because the suspensions were getting hot and lengthening when it was very cold out. The problem was that our temperature control sensors were mounted on the walls, and were influenced by the temperature of the walls. As a result, the HVAC overheated the LVEA to keep the wall sensors at the same temperature when it was very cold out, or over-cooled the LVEA when the sun shown on the walls (33320). We moved some of the sensors to cable trays by the vacuum enclosure to combat this problem, but, since the sensors on the cable trays dont provide full coverage, we still use many of the wall sensors. Yesterday we took more of the wall sensors out of the control average because we are having some problems in this cold snap with the suspensions lengthening.

In addition, TJ altered the LVEA temperature figure of merit to focus on the sensors on the cable trays so that we would be alerted to temperature increases at the chambers, where previously we were mainly monitoring the temperature at the walls.

The figure shows which sensors are now being used (checked boxes). It also shows the new FOM - the first 4 channels are on cable trays near the IFO.