cheryl.vorvick@LIGO.ORG - posted 01:31, Monday 02 September 2019 - last comment - 17:18, Monday 02 September 2019(51673)
IM4 pitch alignment in and out of lock, O3
While watching H1 relock I can see IM4 alignment chaging by around 60urad, so I searched O3, and see that in April the dirrefence was around 15urad, then in early May that drops to 5-6urad, then it's about 10urad, and by May 9th it's about 40urad. It continues to change periodically, though remains at 40+urad, and currently the change is 60urad. What's interesting is that the big change does not cooincide with the increase in power to 37W. Plot shows IMC_IN and IM4 pitch, 150 days. Chart shows changes every month, O3.
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two additional plots showing IM4 Yaw:
- plot 1 shows IM4 pitch and yaw and ISC_LOCK_STATE_N as H1 goes from unlocked to NLN.
- upper left plot is IM4 yaw, and the ISC_LOCK_STATE_N is in the 400's, IM4 yaw is moved almost 30urad, and then back again
- at the same time, IM4 pitch move more than 60urad
- plot 2 shows 150 days, the same time fram as the original post's attached plot
- this plot has both IM4 pitch and yaw
- upper plot is yaw, and toward the right side og the plot, one can see that IM4 yaw is now routinely traveling around 25urads, and then back, during lock aquisition
- this change coincides with IM4 pitch increasing it's motion during relocking from around 40urad to 60urad
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