I was told before that only one of the QPDs on TMSX see the IR transmission. I wanted to see how bad the problem is, so I looked at the the QPD signals for X and Y when night people were having night locking fun.
I'm disappointed to see that both of the X QPDs see nothing (attached, ch3 and ch6). QPD matrix elements and gains are correct, it's just that there's no photon. How come?
Y looks OK.
I saw an entry in the LLO log where they were able to flash the QPDs through a viewport during a time when they suspected they had a non-functional transmon QPD. If you begin to suspect the actual QPD functionality, perhaps you can try that. Otherwise, you can always give me a call and we can go over a functional check to be done chamber-side.
too far out of alignment.
Daniel told me that, after people played with X IR QPDs and saw some light, he moved picomotor of M4 (that is the harmonic separator the reflects IR but transmits green) because there was no IR on ISCTEX any more. After Daniel's treatment no IR light was seen on QPDs.
That's a long time ago.
No, Rich, I'm not suspicious about electronics.