X arm ALS lock glitchy

The X arm green lock looks much more glitchy than usual. This is an intermittent problem, it seems to fade away after a while the cavity is locked.

ALS DIFF find IR failing

This morning the ALS DIFF find IR state failed a few time, without being able to find the Y arm resonance. I had to tune the DIFF offset manually.

Soft and SRC angular loops

Yesterday we noticed that when the soft loop were closed, the SRC1 and SRC2 yaw loops were kicked out of zero, and took a long time going back. Therefore I locked the IFO up to ENGAGE_SRC_ASC, and did a couple of tests:

• I slowly moved the soft degrees of freedom to zero the error signals. The IFO stayed locked and I saw no oscillation in any of the ASC loops.
• Then I characterized the SRC1 and SRC2 yaw loops, by adding offsets to the input and looking at their impulse response. They were extremely slow. I could increase the gains from 1 to 4 (SRC1_Y) and from 20 to 100 (SRC2_YAW), getting a reasonable response and no sign of instability
• I did the same test with the SRC1 and SRC2 pitch loops, although we did not see any large excursion with them when closing the soft loops. I could increase their gains to 4 and 100 as in yaw, so I put those values in the guardian as well for symmetry

The new gain settings for SRC1 and SRC2 yaw loops are in the guardian.

I also measured the response of the transmission QPD signals to the soft degrees of freedom and the TMS, and computed a new sensing matrix, which is now in the guardian. See 43749 for details.

Full IFO alignment is inconsistent with initial alignment

We have now seen at least twice that if we adjust the soft degrees of freedom when locked in full IFO, and optimize for the best recycling gain, we end up with an alignment which is not good when we lost lock. Every time we lost lock after moving the soft degrees of freedom the IFO ends up in a alignment configuration that does not work for DRMI lock.