J. Kissel
I'm are trying to figure out the best metrics for showing off the improvements to the OSEM PD's satellite amplifier's whitening improvements.
Thus far, Oli's been using the input to the damping loops as the metric, using a regression of the corresponding ISI's GS13s to subract out a fit of how much of that sensor signal is seismic noise, and dividing out the loop suppression -- see LHO:86149 for the most recent examples comparing before vs. after the sat amp upgrade.
Without the presence of any other noise or control signals, that should be a fair comparison of the OSEM PD's sensor noise improvement.
However, for a lot of these comparisons ISC control signals are complicating the comparison -- usually at low frequency where ISC control is typically distributed to the top masses.
I use this aLOG as an example of how to better understand this contribution breakdown for a relatively simple suspension -- H1SUSMC1 -- which only has P and Y ISC control from the IMC WFS. (Longitudinal control for IMC L is fed to MC2). This will also be interesting in the future
:: in the context of how SPI and other sensors may improve the cavity motion,
:: in terms of what DOFs and loop's worth of control drive at which frequencies -- important for discussions along the lines of "DOF [blah] is dominating the control signal, and the actuator cross-coupling for M1 drive of DOF [blah] to M3 optic DOF [blorp] is large, so let's reduce the DOF [blah] drive," and
:: in terms of whether/where implementing ISI GS13 estimator feedforward will improve things.
To understand how much of the damping loop *error* signal is composed of ISC *control* signal, I look compare the
- the ISC control signal,
- the DAMP *control* signal, against the
- the MASTER total control request,
all calibrated to the same point in the control system -- where the control output is summed and in the OSEM basis; just down-stream of the EUL2OSEM matrix, and just upstream of the COILOUTF filters which compensate for the coil driver frequency response (uninteresting for this study).
Pitch -- the T1T2T3 actuators
(3) Attachment 3 Pitch Noise Comparison excerpt from Oli's LHO:86149. These are times when the IMC was LOCKED, so there should be ISC control. But, see the expected factors of 2x-to3x improvement in the OSEM noise below ~5 Hz. So, maybe the ISC control is so low in bandwidth that its affect isn't impacting this study. But, we can see that there's clearly some other loop suppression that has not been accounted for, so maybe it *is* high bandwidth? Let's find out.
(1) Attachment 1 Comparison of ISC pitch, DAMP pitch, as well as the other DAMP DOFs that use the T1, T2, and T3 actuators -- Vertical and Roll -- control signals.
Here, we can clearly see that the damping loops are dominating the T2 (and thus T3) control signal above ~ 0.5 Hz, or conversely, the IMC WFS DC coupled control is dominating below 0.5 Hz.
(2) Attachment 2 shows that the T2 and T3 sensors receive identical request (mostly an out-of-phase combination of Pitch and Roll damping request, as expected from the EUL2OSEM matrix), and T1 drives mostly Roll damping request. The vertical drive request is subdominant at all frequencies.
(3) Attachment 4 shows the open loop gain and loop suppression TF magnitudes for pitch. The loop suppression here looks very much like the inverse of the shape of the ASD left in the pitch regression, making me worried that Oli's automated regime for removing the loop suppression isn't perfect... I'll ask.
Yaw -- the LFRT actuators
(7) Attachment 7 The before vs. after comparison of OSEM noise
(5) Attachment 5 Similar comparison of ISC vs. relevant DAMP control -- showing IMC WFS control dominating only below ~0.2 Hz.
(6) Attachment 6 As expected from the EUL2OSEM matrix, the LF and RT actuators receive the same control.
(8) Attachment 8 Shows the open loop gain and loop suppression TF magnitudes for the Yaw damping loop.
Here's the characterization data and fit results for S2001292, assigned to FC2 M1's T1T2T3LF OSEMs (Fil refers to this just FC2 T1T2T3LF above). Note that Fil flip-flopped the "Old" vs. "New" serial numbers in the main aLOG above. This sat amp is a US 4CH sat amp, D1900089 / D1900217, not a UK 4CH sat amp, but this type and all sat amps are now covered in -v2 of ECR E2400330. The data was taken per methods described in T080062-v3, using the diagrammatic setup shown on PAGE 2 of the Measurement Diagrams fromLHO:86807.
The data was processed and fit using
${SusSVN}/trunk/electronicstesting/lho_electronics_testing/satamp/ECR_E2400330/Scripts/
plotresponse_S2001292_FC2_M1_T1T2T3LF_20250804.m
Explicitly, the fit to the whitening stage zero and pole, the transimpedance feedback resistor, and foton design string are
Optic Stage Serial_Number Channel_Number OSEM_Name Zero_Pole_Hz R_TIA_kOhm Foton_Design
FC2 M1 S2001292 CH1 T1 0.0935:5.11 121 zpk([5.11],[0.0935],1,"n")
FC2 CH2 T2 0.0910:4.98 121 zpk([4.98],[0.0910],1,"n")
FC2 CH3 T3 0.0923:5.05 121 zpk([5.05],[0.0923],1,"n")
FC2 CH4 LF 0.0923:5.05 121 zpk([5.05],[0.0923],1,"n")
The attached plot and machine readable .txt file version of the above table are also found in
${SusSVN}/trunk/electronicstesting/lho_electronics_testing/satamp/ECR_E2400330/Results/
Per usual, R_TIA_kOhm is the default 121 kOhm is not used in the compensation filter -- the magnitude of the measurements didn't need me to adjust them; I was able to get a good phase and magnitude fit by only adjusting the zero frequency. Here's the characterization data and fit results for S2001288, assigned to FC2 M1's RTTSDxxxx OSEMs (Fil refers to this just FC2 RTSD above). Note that Fil flip-flopped the "Old" vs. "New" serial numbers in the main aLOG above. This sat amp is a US 4CH sat amp, D1900089 / D1900217, not a UK 4CH sat amp, but this type and all sat amps are now covered in -v2 of ECR E2400330. The data was taken per methods described in T080062-v3, using the diagrammatic setup shown on PAGE 2 of the Measurement Diagrams fromLHO:86807.
The data was processed and fit using
${SusSVN}/trunk/electronicstesting/lho_electronics_testing/satamp/ECR_E2400330/Scripts/
plotresponse_S2001292_FC2_M1_T1T2T3LF_20250804.m
Explicitly, the fit to the whitening stage zero and pole, the transimpedance feedback resistor, and foton design string are
Optic Stage Serial_Number Channel_Number OSEM_Name Zero_Pole_Hz R_TIA_kOhm Foton_Design
FC2 M1 S2001288 CH1 RT 0.0936:5.12 121 zpk([5.12],[0.0936],1,"n")
FC2 CH2 SD 0.0921:5.04 121 zpk([5.04],[0.0921],1,"n")
FC2 CH3 xx 0.0923:5.05 121 zpk([5.05],[0.0923],1,"n")
FC2 CH4 xx 0.0923:5.05 121 zpk([5.05],[0.0923],1,"n")
The attached plot and machine readable .txt file version of the above table are also found in
${SusSVN}/trunk/electronicstesting/lho_electronics_testing/satamp/ECR_E2400330/Results/
Per usual, R_TIA_kOhm is the default 121 kOhm is not used in the compensation filter -- the magnitude of the measurements didn't need me to adjust them; I was able to get a good phase and magnitude fit by only adjusting the zero frequency.