[Keita, Mayank]

We optimized the ALSY PDH demod phase of the CM board.

We measured the OLTF of the PDH loop using the setup detailed in https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=82166 at 3142Hz. (Note that the raw number measured is 40dB smaller than the actual gain due to electronics gain in the generic DAQ filter in the denominator.)

We changed the delay line between the local oscillator and the demod board to maximize the OLTF amplitude. 
Before we changed anything, we measured the ALSY OLTF and it was about 9 dB smaller than ALSX at 3142Hz. As we changed the delay line we eventually had to decrease the IN1 LOCKED gain of the CM board (H1:ALS-Y_REFL_LOCK_LOCKEDGAIN) by 3dB so that ALSY OLTF becomes about the same as ALSX. ALSY locked and ran fine with that setting.

Initial values: Delay line Phase: 223 Degree (421 steps), CM board LOCK IN1 gain +10dB, TF magnitude measured -37 dB.
Tuned value: Delay line Phase: 165 Degree (311 steps), CM board LOCK IN1 gain +7dB, TF magnitude measured -27 dB. 

Attached is the screenshot of before (blue) and after (red) the tuning as well as ALSX (black dotted)