edmond.merilh@LIGO.ORG - posted 09:34, Wednesday 23 November 2016 - last comment - 23:58, Wednesday 23 November 2016(31776)
Difficulty with SRC_ALIGN in initial alignment process
Frequently I find that SRC will not lock properly. I then misalign SRM and look at the spot centering on te ASC_QPD to check the alignment of SR2. Usually I find that it's been driven off diagonally in one direction or the other making it difficult for the loops to align and converge SRM into the cavity. After re-centering I will re-align SRM and re-request SRC_ALIGN and it should lock and converge properly. Maybe some hand alignment will be necessary.
Just a minor note---the QPD one looks at is the AS_C QPD. (i.e. Anti-Symmetric port "C" QPD & not the ASC QPD).