Dan Danny Georgia Craig

Tonight we increased the DARM offset and measured the 9 MHz RIN to DARM coupling, and looked at the noise.  It seems like the 9 MHz RIN to DARM coupling goes down with increased DARM offset.  
At the same time I took DARM spectra and cross-correlations, there was no change in either while the DARM offset was moved.  
This seems to indicate that it may not be the 9 MHz coupling itself which limits us at 40-70 Hz.  
Daniel suggests that the coupling could be carrier-borne intensity noise which trades off differentially with the sidebands.  In other words, carrier power goes up, sidebands go down, and vise versa.  The higher the modulation depth, the larger this coupling could be.  This sort of intensity noise would be invisible to the ISS, which stabilizes total power.  And we know that our input RIN coupling to DARM is higher than for a balanced IFO.
We may try locking the OMC on carrier and exciting the 9 MHz to see how the RIN couples from 9 to carrier.

While Georgia was moving the DARM offset, we saw the 48 Hz hump go away in the DARM spectrum.  Seems like it could be a jitter/scatter peak near the OMC which was washed out by the extra DARM offset light.

We also took a PCAL to DARM sweep and a DARM OLG for the calibration, stored in /ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Measurements/FullIFOSensingTFs/.  From the PCAL to DARM measurement it seems that our very low frequency calibration is off.

I set up some frequency (600-800 Hz) and intensity (1200-1400 Hz) injections, flipped the CO2 mask guardian to ANNULUS, and started Dan and Danny's 400 mW ITMY C02 mask injection at GPS=1234950440 with the following command: python co2_power_temporary_adjust_ITMY.py ITMY -s 'now' -d 7200 -sp 0.4
If you come in tomorrow, please turn off the awgguis on workstation ZOTWS22.