J. Kissel

I've walked through the new front-end (LHO:68961) and MEDM (LHO:68999) infrastructure that supports demodulation of the new(ish) PCALX systematic error lines in order to get it all up and running so that we have a live, real-time estimate of the systematic error in the calibration at any given time. 

This walk through includes: 
    - Turning on the corner station local oscillators to match the parameters of the PCALX end station drive oscillators
    - Installing "BP[linefreq]" filters in each PCAL, DARM, and EXT_SIG banks which band pass the "Opposite" reference PCAL (as it's currently set up, this is PCALX), DARM_ERR, and DELTAL_EXTERNAL. For these, I've chosen, for now, I've chosen a 6th order butterworth band pass, with +/- 0.05 Hz corner frequencies symmetrically surrounding the line, i.e. for the 33.43 Hz line, the FM1 "BP33.43" design is butter("BandPass",6,33.38,33.48). The symmetry ensures that at the line frequency, the transfer function has unity magnitude and zero phase. The +/-0.05 Hz bandwidth means that the peak of the filter's impulse response is around ~15 seconds, with a 1/e time within ~20-30 seconds of the impulse.
    - Installing "LP40s" filters in each following I and Q bank, low-passing the demodulated signal to mitigate contamination of the 1f and 2f components of the demodulation process. I chose 
 and started installing SIG band passes and I and Q low passes. Here, in FM1 of the I and Q banks, I chose a 4th order butterworth, with corner frequency at 0.025 Hz, butter("LowPass",4,0.025). This filter has an impulse response of ~40 seconds, as a compromise between "don't limit my patience in getting the answer" and "don't make the impulse response of I and Q low pass filters shorter than the impulse response of the SIG bandpass."  

All of these filters, the bank inputs, and back outputs have been turned ON, and the filter bank gains have been set to 1.0. 
These settings have all been saved in the OBSERVE.snap (and therefore safe.snap) SDF file(s).
The H1CALCS.txt foton file has been committed to the userapps repo after all the above filters have been installed.

Now we "just" need to populate the EPICs records that account for the flaws in each of the DELTAL and PCAL channels, in the corresponding channels (e.g. for the 33.43 Hz line which is processed by the 5th DEMOD, filling in H1:CAL-CS_TDEP_PCAL_LINE5_DELTAL_PCAL_CORR_REAL and H1:CAL-CS_TDEP_PCAL_LINE5_DELTAL_PCAL_CORR_IMAG). Evan and I will work together to do that tomorrow morning.