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Entry  Tue Feb 25 19:58:06 2020, Hang, Update, IOO, MC2 coil balancing 
    Reply  Wed Mar 11 16:46:25 2020, Hang, Update, IOO, MC2 coil balancing 
Message ID: 15224     Entry time: Tue Feb 25 19:58:06 2020     Reply to this: 15265
Author: Hang 
Type: Update 
Category: IOO 
Subject: MC2 coil balancing 

[Yehonathan, Hang]

We did some quick DC balancing of the MC2 coil drivers to reduce the l2a coupling. We updated the gains in the C1:SUS-MC2_UL/UR/LR/LLCOIL to be 1, -0.99, 0.937,-0.933, respectively. The previous values were 1, -1, 1, -1.

The procedures are the following:

Lock IMC.

Drive UL+LR and change the gain of LR to zero pitch.

Drive UR+LL and change the gain of LL to zero pitch.

Lastly, drive all 4 coils and change UR & LR together to zero yaw. 

We used C1:SUS-MC2_LOCKIN1_OSC to create the excitations at 33 Hz w/ 30,000 cts. The angular error signals were derived from IMC WFSs.

While this time we did things by hand, in the future it should be automated as the procedure is sufficiently straightforward. 

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