We continue to struggle with some of the problems that appeared after Tuesday's maintence period. To summarize these issues:
- We are no longer engaging the CARM boost, with the boost engaged we would loose lock within a few minutes of transitioning to ANALOG_CARM. This could indicate that the frequency noise is higher, or an instability in the IMC or FSS, Craig measured the IMC OLG which seems fine (alog 43733)
- We have an intermittent problem with fast glitches in the ALS X arm locking, which might be because of the PLL or noise that comes from the fiber.
- We have frequently been losing lock in the final stages of the CARM offset reduction. (The transition to REFL9/sqrt(TRX) and the final step to resonance.) These locklosses can be avoided by doing an inital alignment, but it seems that this is less tolerant of small misalignments than it used to be.
- We can no longer engage the ISS 2nd loop.
- The ISS 1st loop has been noisier since the PSL work on Tuesday and the 2nd loop cannot be engaged. Peter King commented here that this is due to having the ISS second loop open and the switches enabled. The 1st attached screenshot shows the problem, that the diffracted power has been noisier since Tuesday. The second attached screenshot shows that about a half an hour ago I disabled the input to the 1st loop, and the noise is unchanged.
- Travis looked at conlog for differences in several systems, and found that yesterday afternoon someone changed the 1st loop gain and switched the PD from PDB to PDA. Apparently no-one remembers doing that, so we switched it back today.