One of the things that I looked at tonight was whether or not I could hold the PRMI on REFL165 at CARM offset of 0, and it turns out that I can. Hooray. The next step was having a look to see if it is actually less noisy than the REFL33 lock.
I calibrated REFL33 and REFL165 to meters (I have the data to do the same for 11 and 55, but haven't done so yet). This way, we can directly compare the signals from each PD.
I scanned between +3 and -3 CARM digital offset (which we think is about 1nm/count while held on ALS), with a ramp time of 10 seconds. I did this several times while the PRMI was locked on both REFL33 and REFL165. Here are the gps times for 8 examples where the PRMI did not lose lock during the sweep:
Here are screen shots from the first REFL33 sweep, and the first REFL165 sweep. DTT can't print 3 plots together, so I'll have to make this nicer later. The top plot is the error signals, calibrated to meters. The middle plot is the control signals, that need to be calibrated to Newtons. The bottom plot is the arm powers, so you can see roughly where we were in the sweep.
We'd like to see a MIST simulation, or perhaps e2e, to see what the predicted disturbance is for each of the error signals during the CARM resonance. We want to make sure that the loops are engaged for all of the degrees of freedom for the simulation.
Recipes for tonight:
REFL165 sometimes has a tough time catching lock by itself, but if you add either REFL33 or REFL55 error signals to the REFL165 signals, it'll catch, and then you can just remove the extra error signals. Also, it doesn't stay locked very robustly unless you include the PRCL FM1 boost.