J. Warner, A. Pele, J. Kissel

Jim has improved the isolation loop design for the HAM2, HAM3, HAM4, and HAM5 ISIs by increasing the frequency / aggression of the Level 3 isolation filters (along with tweaking the UGF and high frequency rolloff such that the aggressive boost remained stable). As such, we have a great deal more feedback gain in the 0.5 to 5 [Hz] region of all DOFs for these HAMs -- the region where the noise performance is typically loop gain limited -- and therefore the performance improvement has scaled linearly with the gain increase. See "IsoFilterComp" attachments.

We didn't have noise budget yet to prove it, but Jim had recognized that HAM6, the most recently designed chamber had much better performance, and much high boost frequency. 

Arnaud has gathered performance data comparing platform displacement before and after the change, which confirms the goodness locally. See "PerformanceComp" attachements. We didn't grab / compare the rotational degrees of freedom but these have also improved. Now that Arnaud has installed properly-matched, sensor correction, gains (see LHO aLOG 16208), we should expect a little bit better translational performance, so we'll compare again and make sure we capture rotational DOFs. Further, we plan to use calibrated DRMI cavity control signals to ensure that what we've done locally is good for the IFO.

The parameter files for these new current designs can be found here:
HAM2/Scripts/Control_Scripts/Version_3/Hori_ISO_H1_HAM2_Lv3_HR_2014_10_23.m
HAM2/Scripts/Control_Scripts/Version_3/Vert_ISO_H1_HAM2_Lv3_HR_2014_10_22.m
HAM3/Scripts/Control_Scripts/Version_3/Hori_ISO_H1_HAM3_Lv3_IMC_HP_2013_01_16.m
HAM3/Scripts/Control_Scripts/Version_3/Vert_ISO_H1_HAM3_Lv3_IMC_HP_2013_01_16.m
HAM4/Scripts/Control_Scripts/Version_3/Hori_ISO_H1_HAM4_Lv3_HR_2014_09_22.m
HAM4/Scripts/Control_Scripts/Version_3/Vert_ISO_H1_HAM4_Lv3_HR_2014_09_16.m
HAM5/Scripts/Control_Scripts/Version_3/Hori_ISO_H1_HAM5_Lv3_2014_09_25.m
HAM5/Scripts/Control_Scripts/Version_3/Vert_ISO_H1_HAM5_Lv3_2014_09_25.m