40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Entry  Thu Jun 17 17:09:44 2010, Alberto, Update, LSC, Short Cavity Length Adjustments 
    Reply  Fri Jun 18 13:47:20 2010, Koji, Update, LSC, Short Cavity Length Adjustments 
       Reply  Fri Jun 18 15:07:26 2010, Alberto, Update, LSC, Short Cavity Length Adjustments 
Message ID: 3087     Entry time: Fri Jun 18 15:07:26 2010     In reply to: 3086
Author: Alberto 
Type: Update 
Category: LSC 
Subject: Short Cavity Length Adjustments 

Quote:

You should have been in my lecture yesterday!
Power in the cavity is not a good index (=error signal) to judge the optimal length.
You should look at the phases of the length signals. (i.e. demodulation phase which gives you the maximum amplitude for CARM, PRC, SRC, etc)

You must move the SRC and PRC lengths at the same time.
The resonance of f1 (mostly) depends on the PRC length, but that of f2 depends on both the PRC and SRC lengths. 

Right. Ultimately the phase gain inside the cavity is what we look at. Calculating that for the SBs inside PRC and SRC is actually the first thing I did.

But I kept getting very small angles. Too small, I thought. Maybe there was some problem in the way I calculated it.

Then I made a power analysis to check if the SBs were getting affected at all by that 0.7degree phase shift they're picking up in the arms.

I wanted to show the point where I am, before leaving. But, I keep working on it.

ELOG V3.1.3-