WP 6488
To test the host box as the source of the problem on the EndY PEM STS mounted with the BRS, we switched the HAM1 HEPI Z sensor correction around 10am when the IFO brock lock. This is the only platform and DOF using the HAM2 STS. This has been the configuration since 14 Nov 2016, but Jim does not nelieve this switch from the ITMY seismometer made any improvement in the HAM1 isolation. The sensor correction is directed to the IPS and the crossover to roll the IPS out of the blend is 700mHz. The HAM2 and the ITMY STSs show unity TF and 0 phase below about 2 Hz, see attached. Meanwhile the HAM2 GND STS is off and the Host Box is pulled; cables remain.
I'll post some performance metrics before and after. Once we are sure the performance is not compromised, I'll switch the Host Box at EndY to see if the Glitching is corrected.
Attached are XFR functions and coherence plots comparing the ground motion and CHARD INs and REFL_A_DC OUTs for Ptich and Yaw before the switch to ITMY and after the switch. The reference pale thick lines are before with the HAM2 STS SC. The current dark thin lines are after with HAM1 using the ITMY for the Z sensor correction.
Certainly there is no terrible impact and all differences are suttle. The IFO locked right up after the switch and range seems to be nominal. Caveat: I took the Host Box from the HAM2 STS so I can not exactly compare the after coherence with the before. The coherence & TFs between the two STSs (see in main post) suggests this comparison is kosher.
I expect to use this as evidence to keep this configuration. If commissioners want to see other data for this case, please see me.
