Alexa, Evan, Gabriele, Sheila
We have closed 6 low bandwidth loops with DRMI locked with arms off resonance today, based on what we learned from talking to LLO yesterday:
INP1: REFLA9I-REFLB9I -> IM4 PIT and YAW
PRC2: REFLA45I-REFLA9I -> PR2 PIT only (YAW signal seems to have an offset)
SRC1: ASB36I-> SRM pit only, although error signal loks OK for Yaw as well
MICH: ASB 36Q -> BS, PIT and YAW
In the past we had phased AS36 to maximize the BS signal in Q, but we noticed today that the Q signal is contaminated by SRM. We rephased AS B 36 to minimize the SRM signal in Q, this reduced the SRM pitch motion seen by AS36 B Q by 40 dB.
We have not attempted to close the AS_C-> SR2 loop, since we are far off center on AS_C. It seems that we will have to check search for the alignment that minimizes clipping on the Faraday and use picomotors to re-center AS_C,; we already know that we are clipping on AS_C when we are well aligned for the OMC PDs. (alog 16831 ). Despite this, it looked like ASB 36 I was a decent signal for SRM in both pitch and Yaw.
Nice progress all around on alignment controls! For AS36, what is the phase difference between maximizing for the BS and minimizing the SRM?
We moved the phase by 15 degrees (we only tuned this to within 5 degrees)