Reports until 14:11, Thursday 07 October 2021
H1 SUS
betsy.weaver@LIGO.ORG - posted 14:11, Thursday 07 October 2021 - last comment - 16:39, Thursday 07 October 2021(60173)
HAM5 minor work today

Still waiting for baffle parts for various HAM5 assemblies, TJ and I went into the chamber today to recenter the OFI AOSEMs.  We ended up resetting the offsets and gains since the Open Light Voltages are different from when tehy were first set years ago.

We also turned on the AUX HAM5 alignemnt laser and did a final alignment of ZM6 pointing to the center of the ZM5 piezo driven optic.  We then turned it over to the SQZ team to continue in HAM7.

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betsy.weaver@LIGO.ORG - 15:17, Thursday 07 October 2021 (60175)
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Attached are pix of the current OSEM settings, as well as he SDF showing the old setpoint and the new setting.  Will accept in SDF now.

The 3 AOSEMs on this OFI SUS seem to have come down in OLV a few thousand counts since the setpoints were set.  Today we noticed that opening the cover to the chamber and working in there seemed to change the OLVs a few tens of counts.  Temperature variation probably?

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jeffrey.kissel@LIGO.ORG - 16:39, Thursday 07 October 2021 (60179)
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Just to ease any worry as to whether 10s of counts change in OLC matter: "10s" of counts are equivalent to displacements of order 1 um. Take, 50 counts, for example.

50 * (40 V_diff /2^16 ct) * (1 V_se / 2 V_diff) * (1 A / 120e3 V) * (1e6 uA / A) * (0.7 mm/ 76.25 uA) * (1e3 um / 1 mm) = 1.16 um
as opposed to the peak range of the "perfect" OSEM which has 30000 cts or ~700 um to play with. 
So if it's temperature (or IMO, more likely, it's the extra, or less, ambient light from having the chamber parachute open), you need not worry about a 50 / 30000 = 0.001 or 0.1% error in the calibration gain of 30000/OLC.

Conclusion -- 10s of counts error (or uncertainty due to environmental conditions) don't matter.

(This is also why entering in OLC compensating offsets and gains can be safely entered in at "10s of counts" accuracy.)