Anamaria, Sheila, Robert
We scanned the biases for three test masses to find the coupling minimum for currents that we injected onto the building ground. The optimal ETMY bias was 115 V in January of 2023, 170 V in Aug. (72308) and 200 V now. With ITMX at 0V, the optimal for ITMY was 60 V in March of 2023 (68053) and -222 V now, The figure shows some of the bias scans.
On the 2nd, Robert Anamaria and I found settings that would set the biases to these values, but the EY value hasn't been correctly applied in the automated relocks since. (77647)
For ETMY, L3_LOCK_BIAS_OFFSET should be -4.9 while the L3_LOCK_BIAS_GAIN is -1 to produce a voltage readback of 200V. I've reset this in the guardian, which I might have done last week with a typo.
This has now been loaded so shoud be at the correct value from 16:00UTC 07 May 2024 77674 .