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Entry  Wed Mar 10 00:32:03 2021, gautam, Update, LSC, PRFPMi PRMI3f_ALSsensMat.pdf
    Reply  Thu Mar 11 01:45:42 2021, gautam, Update, LSC, PRFPMi 
Message ID: 15900     Entry time: Thu Mar 11 01:45:42 2021     In reply to: 15892
Author: gautam 
Type: Update 
Category: LSC 
Subject: PRFPMi 
  1. PRM satellite box indeed seems to have been the culprit - shortly after I swapped it to the SRM, its shadow sensors went dark. I leave the watchdog tripped.
  2. I still was unable to realize the RF only IFO
    • Clearly my old settings don't work, so I tried to go about it systematically. First, try and transition CARM to RF, leave DARM on ALS.
    • As usual, I can realize the state were the arm powers are ~100, and the two paths are blended. 
    • But I'm not able to completely turn off the CARM_A path without blowing the lock.

Pity really, I was hoping to make it much further tonight. I think I'll have to go back to the high BW POX/POY lock, and also check out the conversion efficiency / noise of the daughter board on the REFL11 demod board. Compared to before my work on the RF source, the demod phase for the PRMI lock using REFL11 as an error signal has basically necessitated a change of the digital demod phase by 180 degrees - so I made the appropriate polarity changes in the CM_SLOW and AO paths (the assumption is that CARM in REFL11 would require the same change in digital demod phase, and I think this is a reasonable assumption - indeed, with the arm powers somewhat stable ~100, if I look at the PDH signal in REFL11 I and Q, it does seem to show up largely in the I quadrature (pre digital phase rotation). Anyway, with so many weird effects (wonky PRM suspension, strange PRMI sensing etc etc, who knows what's going on. This will take a systematic effort.

I defer the electronics characterization for the daytime (if I feel like I need it tomorrow I'll do it, else. Koji has said he can do it on Friday).


 I was unable to fully hand off control from ALS-->RF, I suspect I may be using the wrong sign on the AO path (or some such other sub-optimal CM board settings). I'll hook up the SR785 and take some TFs tomorrow, that should give more insight into what's what. 

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