After a lock loss this morning Sheila and I spent some time looking further into the mode spacing for ALS (alog80065). We each took an arm and looked at the mode spacing and peak heights at good alignments and some not as good alignments. This exercise didn't yield any major revelations, but did confirm that our Y arm definitely doesn't have perfect mode matching, X arm seems to be better than Y. 

Attachment 1 - ALS Y 00 mode to 2nd order mode spacing. This showed that yesterday Sheila and Ibrahim missed the small 1st order mode between these and Sheila has sinced updated their FSR and FHOM values (alog80076).

Attachment 2 - An example of ALS Y locking below the max flashes, showing that some of our power is in the higher order modes.

Attachment 3 - ALS X comparison of attachment 1

Attachment 4 & attachment 5  - ALS X 1st order peak spacing and height for an okay alignment (4) vs a better alignment (5).

Attachment 6 & attachment 7 - Same as above but for the 2nd order modes.