Abstract

In conjunction with the iHPCD replacement, I updated the some parameters in ETMX_TM_COILOUTF_HP_H{1, 2, 3, 4}. The updates include proper cancellation of dewhitening stage effects and confirmation of consistent actuator efficiency increase. The online reconstruction filter has also been updated accordingly to reflect these changes.

Actuator efficiency of ETMX TM:

H_etmxtm = -3.90899e-14 @ 10 Hz (+2.934 % klog#33609, excluding the effect of this filter update, the impact is approximately -0.38%)

A similar procedure will be required again after replacing the currently tested coil driver ( klog#33854 ) for ETMX_TM_COILOUTF_H{1, 2, 3, 4}.

Additional Notes

The filters ETMX_TM_COILOUTF_HP_H{1, 2, 3, 4} have been updated to reflect the newly measured transfer functions (see DAC wiki).
Instead of incorporating the effect of varying dewhitening stages into the actuator efficiency, I explicitly canceled this effect by adding a low-frequency (~0.03 Hz) zero/pole pair to Sim-DW{1, 2, 3} inside ETMX_TM_COILOUTF_HP_H{1, 2, 3, 4}. After updating the filters, I confirmed that the interferometer successfully reached the "OBSERVATION_WITHOUT_LINES" state.

As shown in Fig.1 and Fig.2, comparing measurements before and after the filter update for both (ETMXTM → DARM) / (XPCAL → DARM), we observed an increase of approximately 3.3% in the actuator efficiency of ETMXTM:

( 0.51923 / 0.50249−1 ) × 100 ≈ 3.331%

This result is consistent with expectations (~3.2%) under the current PRFPMI configuration, in which two dewhitening stages are enabled for the ETMX TM.