Jenne, Jim, Chiara

Today we tested the filters for MCL signal from the LSC filter matrix: there is an AC coupling and the int3 filter, both shown in first attachment. The int3 filter is the same controller filter that LLO is using.  We didn't have time to measure ISI->MC2 for ourselves (because locking is going on), but we figured that it should be pretty similar between the sites.  Perhaps we can improve further when we have a chance to measure our own plant.  Jenne isn't sure why LLO is okay without AC coupling - here at LHO the DC drive to MC2 can be quite high, and we don't want to integrate that up and saturate the HAM3 ISI actuators.

In second attachment there are plots of the result: the green line is a measurement taken while the new portion of the system was offline, while the pink trace is online. In both cases, the CPS-only offloading of differential HAM2-HAM3 motion was on.  Also, today we've had sensor correction on (recall that in past alogs we've done the tests with sensor correction off since people were working in the LVEA). The two plots show the MC2 WIT and the ground motion behaviour. The online test on MC2 shows an improvement over the offline conditions below 100mHz while the ground motion does not show any variation. It is reasonable then to think that the good effect on MC2 is entirely due to the filters.

Next step will be to test PRCL offloading on HAM2 and HAM3.