Ivey used the ISO calibration measurements that I took earlier (85906) to calculate what the OSEMINF gains should be on SR3 (85907), and this script also calculates what it thinks the compensation gain in the DAMP filter bank should be.
The next step is to use OLG TFs to measure what values we would use in the DAMP filter bank to compensate for the change in OSEMINF gains, and we can compare them to the calculated values to see how close they are.
I took two sets of OLG measurements for SR3:
- a set with the nominal OSEMINF gains
T1: 1.478
T2: 0.942
T3: 0.952
LF: 1.302
RT: 1.087
SD: 1.290
- a set with the OSEMINF gains changed to the values in 85907
T1: 3.213
T2: 1.517
T3: 1.494
LF: 1.733
RT: 1.494
SD: 1.793
Measurement settings:
- SR3 in HEALTH_CHECK but with damping loops on
- SR3 damping nominal (all -0.5)
- HAM5 in ISOLATED
Nominal gain set:
/ligo/svncommon/SusSVN/sus/trunk/HLTS/H1/SR3/SAGM1/Data/2025-07-22_1700_H1SUSSR3_M1_WhiteNoise_{L,T,V,R,P,Y}_0p02to50Hz_OpenLoopGainTF.xml r12478
New gain set:
/ligo/svncommon/SusSVN/sus/trunk/HLTS/H1/SR3/SAGM1/Data/2025-07-22_1800_H1SUSSR3_M1_WhiteNoise_{L,T,V,R,P,Y}_0p02to50Hz_OpenLoopGainTF.xml r12478
Once I had taken these measurements, I exported txt files for each dof's OLG and used one of my scripts, /ligo/svncommon/SusSVN/sus/trunk/HLTS/Common/MatlabTools/divide_traces_tfs.m to plot the OLG for each dof to compare the traces between OSEMINF gain differences and then divide the traces and grab an average of that, which will be the compensation gain put in as a filter in the DAMP filter bank (plots). The values I got for the compensation gains are below:
L: 0.740
T: 0.732
V: 0.548
R: 0.550
P: 0.628
Y: 0.757
| DOF | OLTF measured and calculated DAMP Compensation gains | ISO Calibration measurement calculated compensation gains (85907) | Percent difference (%) |
| L | 0.740 | 0.740 | 0.0 |
| T | 0.732 | 0.719 | 1.8 |
| V | 0.548 | 0.545 | 0.5 |
| R | 0.550 | 0.545 | 0.9 |
| P | 0.628 | 0.629 | 0.2 |
| Y | 0.757 | 0.740 | 2.3 |
These are pretty similar to what my script had found them to be last time before the satamp swap (85288), as well as being very similar to the values that Ivey's script had calculated.
Maybe the accuracy from Ivey's script means that in the future we don't need to run the double sets of OLG transfer functions and can jsut use the values that the script gives.
The compensation gains have been loaded into the SR3 DAMP filter bank in FM7 as well as being updated in the estimator damp banks for P and Y. They have been loaded in but of course, are currrently left off for nominal operations since the OSEMINF gains haven't been updated yet
The OSEMINF gains and these new DAMP compensating gains have been turned on together: 86070