Alexa, Sheila, Keita, Fred, Chris
This morning after we moved the WFS, Alexa remeasured the sensing matrix and got (in counts/urad):
| ETMX PIT | ITMX PIT | ETMX YAW | ITMX YAW | |
| WFS A | -1809 | 828 | -896 | 894 |
| WFS B | -362 | -311 | 370 (coherence 0.7) |
712 |
We also checked the phasing by injecting a signal to the laser frequency (through the PDH servo board) and looking at I and Q from each segment. Then we struggled to lock the loops.
Later on we remeasured the sensing matrix again, several times. We saw that the measurement isn't particularly sensitive to the centering on the WFS. We tried using DTT to do the exicitation, and tried using AWGGUI and letting the excitation run for a few minutes before we took the measurement to avoid any trasients, but that also did not seem to have a big impact.
Some elements were consistent (within 20-30%) each time we measured and consistent between Alexa's morning measurement and the after noon measurements. These were EMX Yaw to WFS A (-900counts/urad average) and ITMX yaw to WFS B (562 counts/urad average) ETMX yaw to WFS B consistently was small and didn't have much coherence, so we have set it to zero. Each time we measured ITMX YAW we got a magnitude of 700-750, but the phase varied, (136, -134, -38, -21, 19). We decided to also set this to zero, and now have a yaw matrix that is just: -1.1 WFS A to DOF 1 (ETMX Yaw) and 1.897 WFS B to DOF2 (ITMX Yaw). This seems to be working OK.
For pitch we got values for WFS A that are consistent with Alexa's measurement from this morning, but not for WFS B. For WFS B PIT we got -630 to -853 coutns/urad ETMX pit and 566 counts/urad ITMX pit, a sign flip compared to the earlier measurement.
Right now we have all four DOFs locked, using the new YAW matrix and Alexa's measurement from this morning for PIT. This seems to be stable, we pushed the gain up a little, so the current gains are -0.002 DOF 1+2 Y , -0.002 DOF 1 PIT, and 0.005 DOF 2 PIT. These have been locked with good build up for about 20 minutes.
I have left 2 excitations running, on ITMX Yaw we are injecting 1 count at 3 Hz into the L2 Lock Yaw filter, and for ETMX 0.3 counts at 1.5 Hz. Hopefully this will stay locked a good part of the night so that we can look at how stable the sensing matrix was overnight.