Commissioning time has been reduced recently by lock losses and other issues, so I have been trying a new technique for determining the ITM biases that minimize coupling of electronics ground noise. I have been making slow adjustments of the bias during observation, recording the times of those slow changes, and then monitoring the coherence between DARM and the current clamp on the electronics grounding cable in the CER for the new settings.

The times of the slow changes during observation mode, and the bias setting I have tried, are listed in 78791, 78767, 78734 and this log. The figure compares the original settings for O4b, the setting that we guessed would be best, 0V,0V, and the setting that was consistently better, ITMX: 0, ITMY: -40 V (a setting of -4 in the offset window).