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Entry  Tue Sep 9 00:34:34 2014, Jenne, Update, LSC, Figuring out where to do DARM->AS55 
    Reply  Tue Sep 9 14:25:46 2014, jamie, Update, LSC, Figuring out where to do DARM->AS55 
    Reply  Wed Sep 10 10:49:39 2014, Manasa, Update, LSC, Y arm green + PSL green mode overlap 
       Reply  Wed Sep 10 21:05:43 2014, Jenne, Update, LSC, Holy sensitivity, Batman! ALS_Y_outOfLoop_10Sept2014.pdfALS_XY_outOfLoop_10Sept2014.pdf
          Reply  Fri Sep 12 00:28:04 2014, ericq, Update, LSC, Holy sensitivity, Batman! ALSoutOfLoop.pdf
Message ID: 10474     Entry time: Tue Sep 9 00:34:34 2014     Reply to this: 10478   10487
Author: Jenne 
Type: Update 
Category: LSC 
Subject: Figuring out where to do DARM->AS55 

This afternoon, after Q and Manasa finished recovering from the activities of the morning, I aligned the IFO, and went to the Yend to touch up the alignment of the green to the arm.  I don't know if it was the alignment (I didn't do the PSL table), or I happened to have a good combination of laser temperatures, or what, but the Yend ALS noise was super good.  After that, the low frequency noise contribution is different lock-to-lock, and I haven't discerned a pattern yet.

One thing that we want to try is to get DARM to AS55 so that we're entirely off of ALS (assuming we've already gotten CARM to sqrtInvTrans).  However, according to Q's simulations, we have to get past arm power of a few before we are within the AS55 linewidth.  I have a DTT running showing me the phase between AS55 and ALSdiff as I reduce the CARM offset, but I haven't been able to get close enough to see the sign flip when CARM is on sqrtInvTrans.  If I just sweep through with both CARM and DARM on ALS, I see the sign flip.  I've tried a few different things, but I have not successfully gotten a transition to AS55 while the arm powers were above 1.  Empirically,  I think I want them at at least 3 or 4.

Koji suggested locking the DRMI rather than PRMI, to widen the AS55 linewidth, but I haven't tried that tonight.  Maybe tomorrow night.

I have made a ruidimentary lockloss plotting script, that I have put in ..../scripts/LSC/LockLossData, but I'm not satisfied with it yet.  Somehow it's not catching the lockloss, even though it's supposed to run when the ALS watch/down scripts run.  I'll need to look into this when I'm not so sleepy.

Q, can you please work on figuring out the phase tracker gain tracker?  It will be nice to have that functional so we don't have to fret about the phase tracker gains. 

Manasa, can you please estimate what kind of mode matching we have on the PSL table between the arm greens and the PSL green?  We *do not* want to touch any optics at this point.  Just stick in a power meter to see how much power we're getting from each beam, and then think about the peak height we see, and what that might tell us about our mode overlap.  If we determine it is total crap, we can think about measuring the beams that go either toward the camera, or the DC PDs, since neither of those paths require careful alignment, and they are already picked off from the main beatnote path.  But first, what is our current efficiency?  Yarm is first, then Xarm, since Yarm seems worse (peak height is larger for non-00 modes!)

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