J. Kissel, A. Staley

Alexa found that an odd discrepancy between her model and measurement of the ALS CARM open loop gain transfer function. It turns out this odd discrepancy uncovered an oversight in the suspension coil driver compensation for the MC2 M2 stage. While this compensation was corrected for the other two modified drivers on H1 PRM and H1 SRM back in September (see LHO aLOG 7644), correcting the compensation on MC2 was skipped in favor of keeping the IMC locked, and then it fell off the radar. While this favor is still in place for this evening's integrated testing activities, we'll fix the problem tomorrow.

In the mean time, the details of the difference in compensation filters are below, so one can include the ratio in one's model:
       Current                              Should Be
FM1    zpk([8.99999],[81.9932],1,"n")       zpk([13],[64.9966],1,"n")
FM2    zpk([1.05],[45.9988],1,"n")          zpk([11;20.9999],[1;209.887],1,"n")
FM6    zpk([81.9932],[8.99999],1,"n")       zpk([64.9966],[13],1,"n")
FM7    zpk([45.9988],[1.05],1,"n")          zpk([1;209.887],[11;20.9999],1,"n")
where "should be" is confirmed by the definitive list of measured poles and zeros for each state of each driver, LLO aLOG 4495