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Entry  Tue May 10 22:56:17 2011, kiwamu, Update, SUS, f2p filters installed on ETMY f2p_etmy.png
    Reply  Wed May 11 11:44:52 2011, kiwamu, Update, SUS, f2p filters installed on ITMY f2p_itmy.png
Message ID: 4682     Entry time: Tue May 10 22:56:17 2011     Reply to this: 4688
Author: kiwamu 
Type: Update 
Category: SUS 
Subject: f2p filters installed on ETMY 

New f2p filters were installed on ETMY. 

The statistical error of the coil gain settings are now about 0.8% at high frequency (i.e. above the resonant freq of the pendulum mode)

 What I did :

 -   measured and corrected the coil imbalances on ETMY using a script called F2P_LOCKIN.py

 -   made the new f2p filters based on the measurements and installed them.

  Next step :

 -  do the same adjustment for all the suspensions including PRM, SRM, BS, ITMs and ETMs


(Notes on F2P_LOCKIN.py)

 F2P_LOCKIN.py is a script that I've made in python. This is basically the same as the old script, f2pratio, but uses the realtime LOCKINs instead of ezcademods.

The script automatically measures the coil imbalances on an optics of interest by driving the local LOCKIN oscillators.

In the first step the script automatically balances the coil gains at high frequency (8.5Hz).

In the next step it gives some coefficients, which basically represent the coil imbalances at low frequency (0.01Hz)

Then with those coefficients one will be able to design the f2p filters.

It is not well polished yet, so I will spend some more times to make it user-friendly and readable.

Example usage : F2P_LCKIN.py -o ETMX

It currently resides in /cvs/cds/rtcds/caltech/c1/scriptss/SUS/


(new f2p filters)

The plot below shows the new f2p filters. Note that they are already installed.


Pendulum mode = 0.982 Hz (according to the wiki)
Q of the pendulum mode = 1 (to avoid ringing of IIR filters)
UL_fz = 0.965125
UR_fz = 1.029517
LL_fz = 0.934231
LR_fz = 0.996562
UL_Qz = 0.982816
UR_Qz = 1.048388
LL_Qz = 0.951356
LR_Qz = 1.014829
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