Gabriele, Dan, Sheila
- We have locked DRMI at 1 Watt.
- We got WFS loops running for PRX and SRY, and added to the guardian the Xarm IR locking and wfs for inital alignment.
- We have focused several of the cameras, and now have better views of many optics.
We did several things today and last night...
First we worked on focusing the cameras on the input arm, ETMX, and both ITMs. Now we have a much clearer view of our interferometer. I also copied the code to align TMSX using the GigE camera from the IAS guardian into the ALS guardian, and tried it out with the cavity locked on green. This kind of works, although the camera centroid is noisy, the noise roughly coresponds to 3 urad of TMS angle. We probably want to get a mask going on the camera to see if that helps.
We are using refl WFS for SRY and PRX. We also attempted this for MICH on the dark fringe, but the signal was too noisy to work well. For all the asc loops, we used FM1+2. For PRX we used REFL B 9 with a gain of -0.0003 for Pitch and 0.003 for Yaw. For SRY we used REFL A 9 with a gain of 0.03 for both pitch and yaw. All of these states are now added to the guardian currently called ISC_DOF ( we will think of a better name). This currently has the states that were in the DRMI guardian that are actually used for initial alingment, plus the arm IR locking states. The graph for this guardian is attached.
After running though the parts of the inital laignment sequence that we have working so far, we locked PRMI at 10 Watts, and steped the power down using the rotation stage, manually correcting the power in DC PWR IN using the offset, and increaseing our gains. We locked 2.8 Watts with a PRCL gain of 50.4 and a MICH gain of 10, and at 1 Watt with MICH at 110 and PRCL at 22 (we measured the loops and adjusted the gains to keep our MICH ugf around 12 Hz and PRCL around 80Hz, suprisingly the PRCL gain had to be increased by less than a factor of 10 to keep the same gain with a factor of 10 decrease in the power.)
We then took some guesses at the gains to use for DRMI at 1 Watt based on Anamaria's document, what we had originally used, and what we needed for PRMI with 1 Watt. After some adjustment, we locked with the parameters shown in the screen shot. DRMI was locked on the sideband at 1 Watt from about 1:57 UTC September 28th to 2:21 when we tried to change a filter and it dropped lock.
The DRMI acquired lock a few more times over the next couple of hours. During one of these I collected loop measurements of the MICH and SRCL loops. The gain settings were:
MICH: 30.0
PRCL: 22.0
SRCL: -200.0
The MICH UGF was 10Hz with 30deg of phase margin (red trace in DRMI_MICH_loop.pdf). Gabriele saw that the ELP40 filter in the LSC MICH bank was eating a lot of phase around 10deg so he installed an ELP70, but I wasn't able to catch a lock with this filter engaged.
The SRCL UGF is 20Hz and it looks like the gain could be increased by a factor of two.
We had measured PRCL during an earlier lock and the UGF was the same as the reference (70Hz wth 40deg).
The SRM and the BS get whacked really hard during the acquisition for DRMI, and I think one of the limitations to robust locking is the L2P noise that is injected when the DRMI tries to grab a fringe. The picture attached shows a trend around the time when the MICH, PRCL, and SRCL loops were triggered. The BS oplev in PIT has a big excursion after the longitudinal actuation is triggered by the fringe crossing (the peak of >20 counts in POPAIR_B).
