A clean set of TFs were previously taken for both SR2 & SRM (HSTS) suspensions (see LHO aLOG entry 12950), to complete Phase 3a power spectra have been taken with damping loops both ON and OFF for all stages. These power spectra measurements have also been directly compared (allhstss_2014-07_24_Phase3a_H1HSTSs_ALL_Spectra_D*.pdf). The plot key is as follows:-

Black Dashed Line = Expected Sensor Noise
Blue Solid Line = H1SUSSR2 2014−07−24_0900
Green Solid Line = H1SUSSRM 2014−07−24_1000

Summary:

Noise floors for both SR2 & SRM are consistent with expectations. However, it should be noted that SRM M1 T3 LF and RT channels exhibit a comb of narrow frequency features above ~20 Hz, which since observed in both damped and undamped power spectra could be induced by ground loops.

All data, scripts and plots have been committed to the sus svn as of this entry.