• Corey had difficulty locking PRMI after the changes to PR3 and ISCT1 alignment we made earlier today (69897). 
• Right now Corey is going to retry initial alignment, hopefully input align will go more smoothly than it did earlier in the evening and allow Corey to lock PRMI.
• If PRMI will still not lock after this, we can move PR3 back towards it's position of this morning. 
  • Right now PR3 is at 151.6 on the yaw slider, this morning it was at 148.5 yaw. 
  • With the current X arm green references and ISCT1 alignment, it seems that we can move PR3 to 150.2 on the yaw slider to have a beatnote of -16dBm.  This should be OK for locking, but means that we have clipping on the way to the trans PD.  To make our automation work with less light on the PD, we need to renormalize it both for Beckhoff and the front end versions of this channel:
    • for Beckhoff we change H1:ALS-C_TRX_A_DC_NOMINAL from 0.054 to 0.02 (can be done through ezcawrite, or from ALS overview, X PDH screen (grey hidden button), X arm green transmission link on the bottom of the screen).
    • the front end version is H1:ALS-C_TRX_A_LF_GAIN, ALS corner overview, TRX_A_LF orange button in the greenpath box lower left.  We set this to 1.35 earlier today, it might need to be more like 4 or 5 to bring the normalized channel to 1 if PR3 yaw is at 150.2 yaw. 
  • After moving PR3 to 150.2 yaw slider and renormalizing, Corey or Ryan would need to redo the inital alignment starting from INPUT ALIGN.Then they can try to lock PRMI.
• If neither oif those work, it is time to think of reverting what we did this afternoon, including the green references for the X arm, the PR3 move, and the alignment on ISCT1.  This is a project probably best left for the morning.

We are still having difficulties with SRY locking, but I haven't looked into what is going on.  If SRY is not locking in an inital alignment step, it is OK to run SR2 ALIGN offload, and move SRM by hand to increase the SRY flashes. 

Editing to add:

Input align wasn't working well because of an apparent dark offset in POP A 45I.  I adjusted the dark offset from -68.9 to -72 to get the signal without flashes to be near zero.  This must be reset by one of the init align guardian states.  This problem has been seen before and TJ attempted to fix it here, but something is still not working.

2nd edit:  We weren't able to get above 30 counts on POP18 + POP90 in PRMI with PR3 at 151.6 yaw slider, so we moved it to 150.2 with the renormalizations above and re did initial alignment of the IR cavities.  Input align wouldn't lock but the flashes were at 1, so we moved on.  SRY has worked twice in a row.  With this lower beatnote we've had an ALS lockloss, I think that if a few more tries at this alignment aren't fruitful it would make sense to cancel the owl and go to the table in the morning.