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Entry  Tue Feb 25 00:00:01 2014, rana, jenne, Update, LSC, reasons that the REFL signals may be degenerate now 
    Reply  Tue Feb 25 02:46:38 2014, rana, jenne, Update, LSC, Changing PRCL offset changes REFL 165 degeneracy PRC_offsetCheck_24Feb2014.pdf
       Reply  Tue Feb 25 14:48:49 2014, ericq, Update, LSC, Changing PRCL offset changes REFL 165 degeneracy MICHvPRCLangle_wOffset.pdfSBprclPeaks.pdf
          Reply  Tue Feb 25 16:07:33 2014, ericq, Update, LSC, Changing PRCL offset changes REFL 165 degeneracy MICHvPRCLangle_wOffset.pdfMICHvPRCLangle_wOffset_fullscale.pdf
             Reply  Wed Feb 26 01:49:08 2014, Jenne, Update, LSC, Changing PRCL offset changes REFL 165 degeneracy DemodPhaseSeparation.pdfPOP_AS_PDvalues.pdf
Message ID: 9676     Entry time: Wed Feb 26 01:49:08 2014     In reply to: 9671
Author: Jenne 
Type: Update 
Category: LSC 
Subject: Changing PRCL offset changes REFL 165 degeneracy 

I have measured the sensing matrix at a variety of PRCL offset values.

DemodPhaseSeparation.pdf

During this each measurement, I also took a 20 second average of the POP 2f signals and the ASDC signal:

POP_AS_PDvalues.pdf

All of this data was taken during a single lock stretch. 

If / when I do this again, I want to go out to larger offsets.  I won't take as many points, but I do want to see how far I can go before I lose lock, and what the phase separation looks like at larger offset values (this time, I stopped at +700 counts which is about 0.7nm, to start checking the negative values. MC has been unhappy, so I wasn't able to take very many negative offset values.) 

I conclude that these sensing matrix measurements do see changes in the phase separation with PRCL length offset (what we saw / said yesterday), but that they do not line up with Q's simulation from this afternoon in elog 9671.

The simulation says that we shouldn't be seeing large phase changes until we get out to several nanometers, however the measurement is showing that we get large phase chnages with picometer scale offsets.  Yesterday, Rana and I said that the offsets due to RAM were small (of order picometer), and that they were therefore likely not important (elog 9668).  However, now it seems that the RAM is causing significant length offsets which then cause poor MICH/PRCL phase separation.

To Do List:

* Confirm MIST simulation with Optickle.

* Look at sensing matrix data pre-lockins (in the raw sensors).

* Check that there is no clipping anywhere in the REFL path (at least out of vacuum), and that the beam is sufficiently small on all 4 REFL diodes.

* Calculate the new PRC g-factor with the new length.

ELOG V3.1.3-