Evan, Peter, Lisa

Today Evan recovered the DRMI alignment after yesterday modifications of the input pointing . We could go back to about x25 times single arm build-up, and we observed again as  the other night  that we need more gain than before in the TR CARM input to make the transition from ALS COMM, and that the CARM TF is  pretty bad . A  previous measurement  showed a reasonable ugf @ 200 Hz and 30 degrees of phase margin. The same gains now cause the loop to oscillate at ~350 Hz, because of a bump in the TF which flattened the response from 200 to 300 Hz. Lowering the gain brings us too close to instability on the other side (~100 Hz), and we lose lock when trying to reduce the CARM offset.
So, unless something else is wrong, as far as we can tell we need to go through again the painful CARM loop tuning that happened a couple of weeks ago to move on.