40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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Entry  Thu Feb 27 01:02:57 2014, Jenne, Update, SUS, Oplev Tuning Party - round 1 PRM_oplevTuning_26Feb2014.pdf
    Reply  Thu Feb 27 22:25:29 2014, rana, Update, SUS, Oplev Tuning Party - round 1 commentary 
       Reply  Wed Mar 5 09:52:31 2014, Jenne, Update, SUS, Oplev Tuning - Cartoon cost function CostFunctionOplev.pdf
          Reply  Thu Mar 6 17:34:03 2014, rana, Update, SUS, Oplev Tuning - Cartoon cost function 
Message ID: 9682     Entry time: Thu Feb 27 22:25:29 2014     In reply to: 9680     Reply to this: 9690
Author: rana 
Type: Update 
Category: SUS 
Subject: Oplev Tuning Party - round 1 commentary 

  in order to Win in Loop Tuning, you must draw a cartoon of the cost function on the whiteboard before starting. Some qualitative considerations from our Workshop:

  1. We want to use the oplev servo to reduce the motion of the mirror in the frequency band where the Oplev is quieter than the mirror, w.r.t. inertial space.
  2. We can estimate the true mirror motion by some simple stack / pendulum model and compare it to the Oplev noise (not the dark noise). There are several contributions to the mirror angular motion due to the cross-coupling in the stacks and pendula.
  3. Below ~0.2 Hz, we think that the oplev is not the right reference, but this is not quantitative yet.
  4. The high frequency noise in the OPLEV ERROR is definitely electronics + shot noise.
  5. We cannot increase the gain of the loop without posting some loop measurements (Bode + steps). Also have to post estimates of how much PRCL noise is being introduced by the Oplev feedback. Oplev feedback should make less length noise than what we have from seismic.

Give us a cost function in the elog and then keep tuning.

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