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Entry  Thu Jul 15 12:21:08 2010, Alberto, Configuration, LSC, PRC and SRC length adjustements 8x
    Reply  Thu Jul 15 15:57:10 2010, Koji, Configuration, LSC, PRC and SRC length adjustements 
       Reply  Thu Jul 15 16:16:51 2010, Alberto, Configuration, LSC, PRC and SRC length adjustements 
Message ID: 3227     Entry time: Thu Jul 15 12:21:08 2010     Reply to this: 3228
Author: Alberto 
Type: Configuration 
Category: LSC 
Subject: PRC and SRC length adjustements 

Lately I've been trying to calculate the corrections to the recycling cavity lengths that would compensate for the phase that the sidebands will pick up from the arms in the upgraded interferometer.

To do that calculation , I tried two quite different ways, although equivalent in principle. They both use the optickle model of the 40m, but the calculation is made differently.

In the first way, I looked directly at the phases of the field: phase of [input field] / [reflected field], phase of [input field at PRM] / [transmitted field at SRM].

In the second way I looked at the demodulation phases of the LSC signals.

The first way is much simpler, especially from a computational point of view. It is the first I tried several weeks ago, but then I had abandoned because back then I thought it wasn't the correct way.

Anyway, both ways gave me the same results for the PRC length.
For the SRC length, the first way has given me a clear outcome. On the other hand, the second way has produced a less clear result.

According to these results, these would be the proposed adjustements to the cavity lengths:
dl(PRC) = -0.0266 m; dl(SRC) = 0.0612 m

I) 1st Way
a) case of arms ideal length (33.86 m)

sidebandPhaseRotation_73433447384.png sidebandPhaseRotation_73433447590.png


b) case arm length = 38.40 m

PRC

 sidebandPhaseRotation_73433447960.png zoom -> sidebandPhaseRotation_73433448864.png

SRC

sidebandPhaseRotation_73433445372.png zoom -> sidebandPhaseRotation_73433449354.png


II) 2nd Way
a) case of arms ideal length (33.86 m)

 demodPhaseVsRecCavLengths_73432637363.png


b) case arm length = 38.40 m

demodPhaseVsRecCavLengths_73433237349.png

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