[Ushiba, Hirose, Aritomi, Fujimoto, Kataoka, Sugioka]

Abstract:

We performed adjustments for DRMI 1f.

Details:

 We achieved DRMI 1f locking,and completed the phasing, decoupling, calibration, and UGF adjustments for DRMI 1f.

First, we performed phasing for POP90I/AS34I because they are used for thresholds in DRMI locking state.
Since there seemed low coherencein excitation measurement, we tuned the demodulation phase to minimize the offset in timeseries of POP90Q/AS34Q While PRMI3f/SRMI1f locked(Figure.1).
We also updated LSC_CUST_OUT_MTRX in DRMI to reflect the values from PRMI and SRMI.
Then, we achieved DRMI 1f locking.

After DRMI locked, we performed the phasing for POP17 and decoupled SRCL from PRCL IN1.
We injected 150.125Hz excitation to SRCL. Then we changed the demodulation phase from -149.6 to -139.6 to minimize the peak in POP17Q.
We also set the K1:LSC-PD_DOF_MTRX_4_9  -0.4 to minimize the peak in PRCL IN1(Figure.2).

Next, we performed the phasing for POP45 and decoupled PRCL from MICH IN1 and SRCL IN1.
We nnoticed that exciting IN1 causes the contamination by the different G in each control loop, so here we injected 150.125Hz excitation to K1:VIS-PRM_TM_TEST_L_EXC.
Then, the PD signal is just the product of excitation and A(Actuator efficiency) which is independent from control loop.
We changed the demodulation phase from 57.87 to 78.87 to minimize the peak in POP45Q.
We also set the K1:LSC-PD_DOF_MTRX_3_11 5.3 and K1:LSC-PD_DOF_MTRX_4_11 -9.5 to minimize the peak in MICH IN1 and SRCL IN1(Figure.3).

Then, we adjusted control gain.
We measured OLTF for MICH, PRCL and SRCL(Figure.4,5,6).
The UGF for each control was approximately 50Hz, 30Hz and 100Hz.
Out-to-In measurement was consistent with the suspension model, which verifies that the IN1 signal is calibrated to nm.

All of these parameter changes were updated in Guardian,and the specific Guardian modifications will be detailed in Hirose-san’s upcoming post.