patrick.thomas@LIGO.ORG - posted 00:00, Tuesday 30 July 2019 - last comment - 09:03, Tuesday 30 July 2019(50901)
Ops Eve Shift Summary
TITLE: 07/30 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC STATE of H1: Corrective Maintenance INCOMING OPERATOR: Jeff SHIFT SUMMARY: Relocking after PSL flow sensor trip. LOG: 23:07 UTC Timesh moving NCAL from LSB to OSB receiving with car, then into optics lab with trolley. Restarted video5 23:28 UTC Timesh through gate 23:36 UTC Timesh going to optics lab 23:44 UTC Timesh out of optics lab 05:40 UTC Lock loss. Diag message: PMC high voltage is off. 05:49 UTC Set observatory mode to corrective maintenance. Called Richard and left a message. Used LLO as a buddy system and went to CER mezzanine to try to find the HV. Could not find any that looked off. Came back. Talked to Peter. Walked me through the Beckhoff and medm screens. Looks like it was a flow sensor trip. Strangely resetting the flow sensor made the diag message about the PSL HV go away. Leaving to Jeff to relock.
This comment is more or less real time. Comments and notes inserted as they come to mind. Attached are two plots of the laser status and the output of the pre-modecleaner high voltage power supply. Also attached is a plot of the high voltage power supply output and the high voltage slider. The slider sets the output of the pre-modecleaner PZT voltage (via the pre-modecleaner servo, although I must admit I do not see where exactly at the time of writing this comment). The slider setting did not change at all, so the voltage change was not caused by an inadvertent grab of the slider. Whilst speaking with Patrick, it dawned on me that the laser may have been off. I asked him to check the PSL_LASER.adl screen. The laser was still on. Then it was obvious that the shutter, which is located after the 70W amplifier, might be closed. I asked Patrick to log onto the PSL Beckhoff computer to check the status of the shutter. He indicated that the EPICS alarm flag was set and that the shutter was closed. I then asked him to reset the shutter via the control room reset. That did not work, which left the the flow sensor reset under the "external shutter request" section of the MEDM screen. This was done and Patrick informed me that the pre-modecleaner high voltage was back. We know that the chiller did not trip out, since the front end laser did not switch off and there was no evidence of water on the chiller room floor. The rest of the system seemed to come back without any problems after the pre-modecleaner locked.For those that may not be aware, this interlock is tied into the 3 flow sensors on the Diode Chiller lines in the PSL enclosure (the Diode chiller is used to cool the on-table power meters not associated with the lasers; the sensors detect whether or not there is flow, they do not measure it). As Peter said above, we know the chiller did not trip as the laser remained on (the Diode chiller's primary responsibility is cooling the pump diode boxes in the Laser Diode Room, so if it turns off, the laser does as well). This is now associated with FRS ticket 13326.