Rana, Alexa, Evan

We wanted to increase the phase margin in the RF DARM loop, so that we have room to increase the UGF.  In the LSC DARM filter module, we have added filter FM9 (zpk([200;200],[400+i*692.82;400-i*692.82],1,"n")), which cancels the two poles at 200 Hz present in our FM8 LLO filter. It also adds a roll off at 800 Hz. See DARMFilter_changes.pdf to compare the TF with FM8 only vs FM8 + FM9. The UGF of the RF DARM loop is 30 Hz with a phase margin ~32 deg (compared to the old ~20 deg margin). I have attached a plot with the modeled and measured RF DARM OLTFs, and one that compares this with the old loop where FM9 is turned off.

Configuration for RF DARM: FM2(z2:p0), FM3 (resG), FM4(z4^2:p1^2), FM8(LL0), FM9(Lead200)

Note, the configuration for ALS DIFF: FM2(z2:p0), FM3 (resG), FM7(SB60), FM8(LL0), FM10(RL33)