J. Kissel https://tinyurl.com/LIGOSUSActuatorTuning Table I've gathered the data necessary for the necessary re-design of the Longitudinal to Angle (L2A) decoupling filters for the UIM/L1 stage of H1SUSETMX. Attached are screenshots. Hang will take care of the filter design. For now, I've turned OFF all previous L2A decoupling filters (which were designed back in 2014, and only relevant for the former incarnation of ETMX). The data can be found here: /ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMX/SAGL1/Data/ 2018-07-31_H1SUSETMX_L1_WhiteNoise_L_0p02to10Hz.xml 2018-07-31_H1SUSETMX_L1_WhiteNoise_P_0p02to10Hz.xml 2018-07-31_H1SUSETMX_L1_WhiteNoise_Y_0p02to10Hz.xml This data was taken (a) After the coils have been balanced (LHO aLOG 42740) (b) With optical lever L2 damping OFF I also attach play-by-play notes, if anyone's interested in playing along in the future. I'm still debating whether it's faster to just do the balancing, or to spend the time scripting.
Jeff K., Hang
We fitted the freq-dependent L2P filters for the L1 stage. We could reduce some coherence below 0.6 Hz where most of the rms accumulates. See the attached image.
The traces were mostly taken when the L2 stage oplev damping was ON. The pink trace in the TF (top-left panel) was taken with the L2 oplev damp OFF. No significant changes in the residual TF was seen. This makes sense because we ff to cancel the torque perturbation before it enters the loop. As a side note, for the ISIFF, the Sidles-Sigg effect should also not affect the cancellation because it is also equivalent of a damping loop mediated by radiation pressure. We cancel the torque perturbation before it enters the loop (or another way to say it is that the loop affects the L drive -> P angle and P drive -> P angle in the same way and they should thus cancel out).
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Details
The filter we fitted is -(L1L -> L3P) / (L1P -> L3P). In the attached PDF it showed the fitted curve and the data. Note that we only have significant amount of rms after the sus resonance and thus we did not pay too much attention to the performance at > 1 Hz.
The zpk form of the filter we currently installed is (s-domain)
zpk( [ -8.529494e+00+i*0.000000e+00; -2.849899e-01+i*2.457525e+00; -2.849899e-01-i*2.457525e+00; ], [ -1.639339e-01+i*2.326488e+00; -1.639339e-01-i*2.326488e+00; -1.519175e-01+i*2.962514e+00; -1.519175e-01-i*2.962514e+00; -1.562506e-02+i*1.332427e+01; -1.562506e-02-i*1.332427e+01; -5.756616e-01+i*4.883264e+00; -5.756616e-01-i*4.883264e+00; -1.793551e-01+i*1.232680e+01; -1.793551e-01-i*1.232680e+01; -3.751634e-01+i*6.337676e+00; -3.751634e-01-i*6.337676e+00; ], -1.154267e+05 )
In case someone wants to play with the data with IIRrational, he/she might want to run in bash
source /opt/rtcds/userapps/release/cds/h1/scripts/setup_anaconda; export PYTHONPATH=/ligo/home/hang.yu/Desktop/pyComm/:/ligo/home/hang.yu/.py_dev/lib/python2.7/site-packages/:$PYTHONPATH; source /ligo/home/hang.yu/.py_dev/bin/activate
This should activate my python installation with IIRrational. The jupyter notebook for the filter calculation can be found at
/ligo/home/hang.yu/Desktop/ASC/l2a/ETMX
We also did a L2A FF on vs off test with the ALS DIFF locked (actuating on ETMX L1 & L3 stages). See the attached plot.
The pink and cyan curves were with the L2A ON. The red and blue ones were with L2A OFF. For the L2A off ones, we could only stay locked for a single measurement. Nonetheless, the subtraction below 0.6 Hz seemed to be decent (around a factor of ~100 subtraction).
