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Entry  Wed Apr 2 01:18:30 2014, Jenne, Update, LSC, Attempt at PRMI+2 arms 
    Reply  Thu Apr 3 00:30:52 2014, Jenne, Update, LSC, Attempt at PRMI+2 arms 
       Reply  Thu Apr 3 03:06:34 2014, Jenne, Update, LSC, Attempt at PRMI+2 arms 
          Reply  Thu Apr 3 18:09:54 2014, ericq, Update, LSC, Attempt at PRMI+2 arms offsetTRY.pdf2dhist.pdfpdh_trans.pdf
Message ID: 9783     Entry time: Thu Apr 3 18:09:54 2014     In reply to: 9781
Author: ericq 
Type: Update 
Category: LSC 
Subject: Attempt at PRMI+2 arms 

So, here's the basic: "We reduced the CARM offset and saw more TRY" plot. 

offsetTRY.pdf

 

As Jenne mentioned, we suspected that we were seeing real displacement information in the sqrtInv signals. (We had incidentally hard switched to the transmon QPDs for all of this)

Here's a 2d-histogram of the ALS CARM error signal vs. the sqrtInv CARM signal (i.e. 1/sqrt(TRX) + 1/sqrt(TRY))

 

2dhist.pdf

This is exactly the shape we expect, which is cool. You can see where we stepped the offsets, too. It looks like the signal gets into it's good linear range when ALS CARM was about -20, which is when TRY was a little under 0.1, which seems pretty early and potentially useful. 

Also, here are snapshots of what REFL11_I and sqrtInv CARM were doing in the last five seconds of time in the above plot, which was shortly before we made the offset push that broke the PRMI lock. If you look really closely, maybe you can convince yourself that there is some common information in them...? It's hard to say. In any case, there is definitely CARM pdh action happening.

pdh_trans.pdf

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