Jenne, Naoki

Today we tried to measure the AS36 and AS72 sensing matrix to see if we could replace the AS36 sensing with AS72 for MICH ASC. Currently, we use AS36 for MICH, AS45 for DHARD, AS72 for SRC1, but the AS RFPDs are tuned for RF36/45, not for RF72 and the AS72 does not have good SNR for SRC1. If we could replace the AS36 with AS72 for MICH, we can tune the AS RFPDs for RF45/72 to have good SNR for both MICH/SRC1.

We tried to measure the AS36 and AS72 sensing matrix by injecting a 8.125 Hz line in MICH P. To avoid the ASC loop suppression, first we tried to turn on the notch filters at 8.125Hz in all ASC. There is a script to turn on/off the notch filters of all ASC in userapps/asc/h1/scripts/notch_8Hz_ON_OFF.py. We tried to run the script in the terminal, but the terminal does not recognize the ezca, so we moved to the guardian shell by typing guardian -i ISC_LOCK. In the guardian shell, we copied line 1-26 in the notch_8Hz_ON_OFF.py to turn on notch filters.

Then we started to inject a 8.125 Hz line in MICH_P_EXC with awggui. As shown in the attached figure, we set the amplitude 0.001 and kept increasing the overall gain to 10000. We clearly saw the 8 Hz line in AS36 sensors, but not in AS72. Since the 8 Hz excitation seems not to have a good SNR for AS72, we will excite the MICH/SRC1 in DC and see the response of AS36/72 sensors next time.

After the measurement, we copied line 29-49 in the notch_8Hz_ON_OFF.py to turn off the notch filters.