J. Oberling, E. Merilh, J. Warner
The PSL tripped this morning, likely due to the flow in laser head 3. As can be seen in this alog, the flow in head 3 (and only head 3) dropped from 0.52 lpm to ~0.47 lpm sometime on the morning of Saturday, 7/15/2017. It is likely this was the cause of the laser trip. I will do more forensics when I am onsite tomorrow. When restarting the cyrstal chiller, the flow in laser head 3 was back up around 0.54 lpm. Maybe something worked its way through the system, causing the laser trip?
When restarting the laser, the Beckhoff software appeared to lose communication with the hardware of the PSL, requiring a reboot of the PSL Beckhoff PC. Once this was done, everything worked fine and the laser came back up. I had difficulty injection locking the 35W FE to the HPO; I believe this is due to the lower power out of the HPO. I engaged the injection locking by turning the RAMP OFF, and monitoring the power circulating in both directions of the HPO. When the circulating power favored the forward direction, I manually engaged the injection locking. This worked the first time and the laser is now back up and running. Ed re-engaged the PMC, FSS, and ISS, and Jim reset the NPRO noise eater. By this time ~30 minutes had elapsed, so I engaged the LRA and the power watchdogs. The laser is now up and running.
J. Kissel filed FRS 8539 for this trip.
Looking at some trends it appears that it was Laser Head 4 that tripped the PSL, not Laser Head 3 as previously surmised. The first attachment shows the 4 laser head flows around the time of the trip. The second shows the flow through Head 4 and the Head 1-4 Flow Interlock, while the third attachment shows the flow through Head 3 and the interlock. It is clear from this that the flow through Head 4 was at the trip point of 0.4 lpm at the time the interlock tripped, while the flow through Head 3 remained above the trip point. It is unclear why the flow through Laser Head 4 fell so fast, possibly something moving through the system causing a glitch with the flow sensor?