Jeff, Evan, Kiwamu,

We changed the delay cycle between the actuation and sensing paths from 4 cycles to 1 cycle in CAL-CS in this evening at around May-12-2015 1:00 UTC. This is going to more correctly reshape the DARM spectrum at around the UGF.

According to the model that Jeff has been working, the expected time delay between the two paths is 40.1 usec which is about 0.657 cycles for a 16 kHz frontend model. This has been consistent with the measured DARM open loop within a phase error of 1 or 2 degrees. Since the CAL-CS accepts only an integer mupltile for the delay cycle, we put 1. Historyically, the previous factor of 4 came from Livingston when we copied their calibration setup (llo 16475).

For more details, see H1DARMmodel_preER7.m in CalSVN/aligocalibration/trunk/Runs/PreER7/H1/Scripts.