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takafumi.ushiba - 20:34 Thursday 09 June 2022 (21089) Print this report
Actuator efficiency measurement of ETMX

I measured actuator efficiencies of TM, IM, and MN stage of ETMX by using LS OpLev.
I excited ETMX from {TM,IM,MN}_TEST_L_EXC @ 6 Hz and measured the spectrum of TM_WIT_L.
Figure 1 shows the measured results of TF from excitations to TM_WIT_L (red:MN EXC, blue: TM EXC, Green: IM EXC).

Current actuator efficiencies from TEST_L of each stage to test mass L motion are as follows:

Actuator efficiency
  AE @ 6 Hz (m/cnt)
TM 3.14e-14
IM 1.48e-13
MN 5.70e-13

Converting above TM actuator efficieny in the same manner during O3GK, TM actuator efficiency is 1.13e-12 m/cnt.
According to CAL wiki, actuator efficiency during O3GK is about 4.6e-12 m/cnt, which is consistent with the current value, considering a factor of 4 difference of EUL2OSEM (EUL2COIL) matrix element.

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takahiro.yamamoto - 21:45 Monday 03 October 2022 (22314) Print this report
Note: Because TM_COILOUTF gain was changed from ~0.5 (O3GK value) to ~1.0 (for unifying the convention with another suspensions),
actuator efficiency from SUMOUT_L_OUT to the displacement becomes twice (6.28e-14@6Hz).

For keeping DARM UGF, gain(0.5) is applied at TM_LOCK_L.
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