[ericq, gautam]
While trying to resolve the strange SRCL loop shape seen yesterday (which has been resolved, eric will elog about it later), we got a chance to put in the correct filters to the "CINV" branch in the C1CAL model for MICH, PRCL, and SRCL - so we have some calibrated spectra now (Attachment #1). The procedure followed was as follows:
- Turn on the LO gain for the relevant channel (we used 50 for MICH and SRCL, 5 for PRCL)
- Look at the power spectra of the outputs of the "A" and "CINV" filter banks - the former has some calibrated filters in place already (though I believe they have not accounted for everything).
- Find the peak height at the LO excitation frequency for the two spectra, and calculate their ratio. Use this to install a gain filter in the CINV filter module for that channel.
- Look at the spectrum of the output of the "W" filter bank for that channel - the plot attached shows this information.
The final set of gains used were:
MICH: -247 dB
PRCL: -256 dB
SRCL: -212 dB
and the gain-only filters in the CINV filter banks are all called "DRMI1f".
Once we are able to lock the DRFPMI again, we can do the same for CARM and DARM as well... |