aLIGO LHO Logbook

H1 IOO

duncan.macleod@LIGO.ORG - posted 16:37, Friday 17 January 2014 - last comment - 14:56, Thursday 23 January 2014(9373)

Updated ODC settings for IMC

[Jeff K, Stefan B, + detchar]

The bitmask defining the summary bit for the Input Mode Cleaner state-vector (ODC) has been trimmed to respond to only those bits recording the ASC WFS switch (bit 1), and the relative power indicators (bits 11 and 12). In this mode glitches in the WFS alignment will be recorded by the relevant bits 2-9 but won't affect the summary bit, and a low-power mode will still result in summary=GOOD. This was tested first at LLO and logged here.

This hasn't been set in the safe.snap, but will be monitored and coordinated over the next few days.

Comments related to this report

laura.nuttall@LIGO.ORG - 14:56, Thursday 23 January 2014 (9502)

Link

We confirmed that when the WFS alignment (mainly DOF2 Pitch and DOF1 Yaw) strays outside of the thresholds set, it does not have a noticeable affect on the calibrated length of the cavity. Attached are ASDs for both LHO and LLO of IMC_X_DQ. Plotted are two nominal times (red/blue lines) when everything is aligned (all the ODC bits are green) and two times (yellow/green) when the WFS are reporting poor alignment (the y-axis is not in counts/rtHz but the units of the channel - m/rtHz (?)). There is no noticeable difference between the four traces on a given plot. For the time being, we feel ok in removing the WFS alignments from the summary bit (as reported) however we plan to do long term studies of what the thresholds for each DOF should be and maybe then they can be re-added to the summary bit.

Question for whoever can answer this - why is LHO so featureless (compared to LLO) and why are the scales (y-axis) so different between sites? Thanks

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