I went through the X arm alignment again, unfortunately the computer crashed before I saved the alog but the centered values for TMS are 147.5 PIT -234 YAW (+10 in pit compared to yesterday, +6 in YAW) ITM 72 PIT -62 YAW (basically the same as yesterday).
It was easy enough to find the pointing of TMS and the ITM using the baffle PDs starting from the last alingment in alog 9191. However, I could not easily find the ETM pointing. I did find the beams on the baffle PDs by doing a slow scan (Strip chat screen shot attached) and found:
with 40dB gain, PD3 has 2.1 V with ETM PIT 292 YAW 44. REFL B then has 15400 counts
with 20dB gain PD1 has 2.6 Volts with ETM PIT 246 YAW 101 Refl B has around 1100 counts.
From this the aligned position should be 269 PIT 72.5 Yaw. This is remarkably different from where I found similar fringing yesterday, 384 PIT -77 YAW. While there was some HEPI commisioning yesterday afternoon, I would have expected this to change the TMS and ETM alingments by the same amount, so either one or the other of these alignments is bad or something moved. Also, the ETM oplev has moved quite a lot.
The PD levels for these alingments seem suspicously low, if the mode matching was perfect I would expect the intensity on the diodes to only decrease by a factor of the ETM reflectivity compared to the straight shot from the transmon (alog 9191) Instead these are a factor of 100 and a factor of 10 lower. Either these are not the right beams or the mode matching could be wrong. There was clearly some fringing on the refl PD and COMM (which I am using as an X arm trans readback for now).
It is possible to find some light on the PDs for ETM alignments that don't make sense (PD1 on the wrong side of PD4 ect), probably a second bounce beam hitting the PD.
I also changed the polarization into the X arm fiber (photo of settings attached).
Once I saw some fringing I was able to "lock the arm" and the "lock" would stay for 10s of seconds although I'm not sure this was really locking to any reasonable mode of the cavity. On the camera I could see that the beam motion is large, we have verry high winds. I also could not go out to the end station to work on the locking because of tumbleweeds, photo attached.
ETM PIT is not affected by HEPI/ISI PIT much if any, only TMS PIT is affected. The fact that OpLev moved much means that your alignment is still bad, it's likely that the baffle PD signal you saw was something other than the direct beam from ETM.