kiwamu.izumi@LIGO.ORG - posted 06:24, Saturday 01 June 2013 - last comment - 12:35, Saturday 01 June 2013(6591)
WFS commissioning : (1) demod phase re-adjusted again (2) MC1 keeps tripping
There was not so much progress on the IMC WFS commissioning yesterday.
From the late evening MC1 started tripping for some reason and this prevents the IMC from locking stably. I made a contact with Arnaud and Mark.
Besides, I re-adjusted the demod phases of WFS_A and WFS_B again. This time I rotated the phase of some of the segments by 180 deg such that all of them shows the same sign in the error signal of the IMC length. This resulted in a more sensible response in WFS_A (e.g. shaking pitch of MC2 gives pitch signals in WFS-A). I didn't get a chance to look into WFS_B yet.
I logged in remotely about 10:30 am and took a look. The suspension was quiet and the alignment offsets were off. All three levels of watchdog were tripped.
I reset the watchdogs with the damping enabled, and it tripped after a few 10s of seconds with much excitation on the OSEMs as if something had been ringing up. The OSEM AC Band Limited path had tripped and there was lots of excitation on the OSEMs (up to ±10000 counts).
I reset the watchdogs again with just the L damping enabled and got the same results.
I turned off the damping entirely and reset the watchdogs, again and after a short time it tripped again, even though no actuation had been going out.
I turned the damping back on and reset the watchdogs while carefully oberving the OSEM inputs and the DC and AC band limited signals. The damping effectively quieted the signals but again after a minute or two things suddenly went crazy as if the suspension had been knocked.
Finally I reset the watchdogs with damping one last time and it's stayed damped for the last hour. So I don't doubt there was a problem but I'm not sure what it was. The HAM2 ISI and HEPI watchdogs were tripped when I checkeda bout halfway through. The MC3 WD was not tripped.