In full lock (with the POP beam diverter open), I rephased POPAIR9 so that the appearance of PRCL is maximized in I, and I rephased POPAIR45 so that SRCL is maximized in I (same strategy as was done for POP).
The changes are as follows:
- POPAIR9: 63° to 64°
- POPAIR45: −45° to −38°.
I don't think POPAIR is used for any LSC at any point during locking or initial alignment, so there should be no issue here.
Then I left the beam diverter open and redid the LSC sensing matrix measurement. Times as follows (2015-01-16 Z):
- PRM: 02:33:25 to 02:35:25
- SRM: 02:36:15 to 02:39:05
- BS: 02:40:35 to 02:42:35
I then left the beam diverter open and collected quiet data from 02:43:30 to 03:32:30. Kiwamu and I had discussed the possibility of cross-correlating the POP and POPAIR PDs in order to look for correlated vertex LSC noise below the PD shot noises (à la the usual DCPD technique for DARM). In the case of POP45Q (attached), the cross-correlation seems to show correlated noise out to high frequencies, at a level of a few below the POPAIR45Q shot noise.
