(Uchiyama, Miyakawa)

We investigated the cause of the laser down in the PSL room this morning.

The first error was "Seed Signal Too Low. Master Fault.". At this point, the maser was ON. First, we turned the amplifier off, unplugged the power cable and USB cable, waited several minutes, and engaged the amplifier again, but the same error message "low seed power "showed up.

Then we increased the master current from 1.1A to 1.2A, and engaged the amplifier again, and it worked. We increased the power up to ~30W, and locked the PMC. However,  during the lock of IMC, the amplifier went down, and the error message " Master Fault" showed up. Meanwhile of this process, we measured the master power at the DC PD for interlock. The value of this PD yesterday was 2.4V vs 1.1A, but today it was 2.7V vs 1.2A, and 2.1V vs 1.1A. It became lower, obviously.

Then we repeated the same thing again with 1.2A, and the amplifier went down during increasing the power to ~30W (actually went down when close to 30W). We did not have enough time this morning, so we stopped at this point, and we turned off both the amplifier and master. We measured the PD voltage for the master laser again at after shutdown, the result was 3.1V vs 1.2A, and 2.4V vs 1.1A, so the power was back.