We continued the ISIFF work today (similar to LHO:42875). We finished the filter design for both EX and IY. Using passive data, a reduction in L3 pitch of x2 - x3 was achieved.

See the first figure for EX, and second for IY. The pink and cyan curves were with the FF off, and red and blue with FF on.

The subtraction in IY was slightly worse than in EX because I manually added an zero at 0 and pole at ~ 0.02 Hz to enforce AC coupling of the IY L2P (the best fit did not give an AC coupled filter automatically), which degraded the subtraction at ~0.2 Hz. This might not be necessary as the motion at <0.1 Hz did not limit the ctrl bandwidth. When we get a chance next time, will try to move the pole to lower freq (e.g. 0.01 Hz) to get better subtraction of the microseismic.

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The measured FF filter and fitting results were also attached.

The raw measurement data were currently put under

/ligo/home/hang.yu/Desktop/small projects/ISIFF/EX and /ligo/home/hang.yu/Desktop/small projects/ISIFF/IY We will mitigate those to the sus svn.

The foton zpk filter for EX is

zpk( [ -1.201315e-03+i*4.951483e-02; -1.201315e-03-i*4.951483e-02; -9.047257e-01+i*1.310103e+00; -9.047257e-01-i*1.310103e+00; -4.135461e-01-i*8.402608e+00; -4.135461e-01+i*8.402608e+00; ], [ -2.145353e+00+i*3.206850e-03; -2.145353e+00-i*3.206850e-03; -5.465923e-01+i*3.000483e+00; -5.465923e-01-i*3.000483e+00; -2.371843e+00+i*7.319342e+00; -2.371843e+00-i*7.319342e+00; ], 3.359477e-02 )

and for IY

zpk( [ 0.000000e+00+i*0.000000e+00; -1.780956e+02+i*0.000000e+00; -5.654532e+00+i*0.000000e+00; -8.399729e-02+i*3.742470e-01; -2.595089e-01+i*7.302161e+00; -8.399729e-02-i*3.742470e-01; -2.595089e-01-i*7.302161e+00; ], [ -1.400000e-01+i*0.000000e+00; -6.449348e+01+i*0.000000e+00; -2.456886e-01+i*2.905084e+00; -1.885957e-01+i*6.295556e+00; -2.111860e+01+i*9.187572e-03; -2.456886e-01-i*2.905084e+00; -1.885957e-01-i*6.295556e+00; -2.111860e+01-i*9.187572e-03; ], 4.341633e-01 )