Today I made OLG measurements of all four IMs with their new damping loops in L, P and Y. I found IM1 damping OLG measurements from 2018 that I used as references in the attached screenshots. I also made the same measurements of IM2, 3 and 4, but I did not include the images as they are all the same response. However, you can view them in my directory in the folder IM_damping. I was not able to save the measurements to the SusSVN where I found the references.
The new damping filters I applied cause a loss of phase above the IM suspension resonance (L and P is 1 Hz, yaw is 0.7 Hz). See alog 60943, last attachment, for all IM HAUX as a reference. Looking at the loop suppression, the gain peaking is minimal. I think these new damping loops will be sufficient for the IMs and not cause any problems. If we wanted to be more precise, we could tune the P and Y loops further, but I think they are similar enough that we can move forward.
After the fix to the /ligo folder structure (LHO:64035), I've copied over and committed these measurements to the appropriate folder in the SusSVN, /ligo/svncommon/SusSVN/sus/trunk/HAUX/H1/ IM1/SAGM1/Data/2022-07-19_H1SUSIM1_M1_WhiteNoise_L_OLG.xml IM1/SAGM1/Data/2022-07-19_H1SUSIM1_M1_WhiteNoise_P_OLG.xml IM1/SAGM1/Data/2022-07-19_H1SUSIM1_M1_WhiteNoise_Y_OLG.xml IM2/SAGM1/Data/2022-07-19_H1SUSIM2_M1_WhiteNoise_L_OLG.xml IM2/SAGM1/Data/2022-07-19_H1SUSIM2_M1_WhiteNoise_P_OLG.xml IM2/SAGM1/Data/2022-07-19_H1SUSIM2_M1_WhiteNoise_Y_OLG.xml IM3/SAGM1/Data/2022-07-19_H1SUSIM3_M1_WhiteNoise_L_OLG.xml IM3/SAGM1/Data/2022-07-19_H1SUSIM3_M1_WhiteNoise_P_OLG.xml IM3/SAGM1/Data/2022-07-19_H1SUSIM3_M1_WhiteNoise_Y_OLG.xml IM4/SAGM1/Data/2022-07-19_H1SUSIM4_M1_WhiteNoise_L_OLG.xml IM4/SAGM1/Data/2022-07-19_H1SUSIM4_M1_WhiteNoise_P_OLG.xml IM4/SAGM1/Data/2022-07-19_H1SUSIM4_M1_WhiteNoise_Y_OLG.xml After discussing with Elenna, she indicates the HAM-A coil drivers were in State 2 (with its switchable low-pass ON) for the these data sets.
DAC noise dominates the IM control drive above 20 Hz or so. The model here assumes 300 nV/rtHz DAC noise with a 1/f knee at 50 Hz, following G1401399-v2 for an 18-bit DAC (20 V pp range).
