keita.kawabe@LIGO.ORG - posted 10:27, Monday 25 July 2016 (28615)
ITM oplevs need more whitening gain, ITMY oplev needs more whitening filters, we could also give ETMX one more whitening filter.
According to T1500556, current settings for test mass oplevs are:
| Whitening gain | Number of active whitening filters | oplev SUM counts | |
| ETMX | 18dB | 1 | 40500 |
| ETMY | 0dB | 2 | 28000 |
| ITMX | 0dB | 2 | 2400 |
| ITMY | 0dB | 0 | 5400 |
ITMY oplev PIT noise is close to the DAQ noise floor at about 3Hz, and the DAQ noise dominates the RMS down to 0.7Hz or so. ITMX is OK for RMS due to double 1:10 whitening, but not much better at 3Hz. Not good for oplev damping.
Also it seems totally fine to use two stages of whitening filters for ETMX.
We can set things up like this (changes in bold font):
| Whitening gain | Number of active whitening filters | 4000*10^(24/20)oplev SUM counts | |
| ETMX | 18dB | 2 | 40500 |
| ETMY | 0dB | 2 | 28000 |
| ITMX | 21dB | 2 | 27000 |
| ITMY | 15dB | 2 | 30000 |
Images attached to this report
