Reports until 18:11, Friday 17 January 2014
H1 SEI
hugh.radkins@LIGO.ORG - posted 18:11, Friday 17 January 2014 (9376)
ETMX ISI Damping vs Isolation

I have a pretty coarse plot of spectra for the ETM interial sensors with damping only and then with 750mHz Blend level1 Isolation compared.  Not a lot happening in the area of interest below ~1Hz.  I did notice that the Rz was worse though.  This shows up mostly below 0.4Hz.  Stefan removed the Rz Isolation but it only recovers about half way back to the damping only spectra.  There is also the cost of noise between 1 & 2 Hz.  The Reference traces are the damping only except the Rz reference 14 & 20.  These two are the 750mHz spectra with the Rz in the loop.  The Current traces are with the Rzs out of the loop.  The next time the ISI is brought back to isolation, the Rz will be back in.  It doesn't sound like removing the Rz made anyone especially happy.  I wanted to take the ISI to greater levels of isolation but the commissioners said they'll work with this for now.

Before going back to damping only I took the isolation from 750mHz everywhere expect Stage1 X Y & Rz where there was 100mHz blends down to T100mHz (T240s included) on the horz dofs.  This did not improve the situation.  I've noticed too that sometimes the scripts stall part way through and with out the script window popping up to show the status, some states may not be what they seem.

Images attached to this report