Evan's script to automatically take frequency and intensity transfer functions is now running. As a reminder, the summing note B path was repurposed for this run. The interferometer won't relock unless we reconnect them. At 4:20 UTC we started changing the TCS X CO2 power from 0.23W to 0.4W. The rotation stage took us on some full circles, but by 04:23 we reached 0.4W. At 4:45 I increased the frequency noise drive by a factor of 5 to gain back coherence. At 6:04 I decreased the power to 0.35W - trying to find the minimal frequency noise point. (The coupling sign had changed.) At 6:34 I reduced it to 0.3W.
It wasn't really clear from this run where the minimum in frequency coupling was (maybe because of the 5 W blast at the start), so I went back to 0.23 W of heating and let the frequency coupling reach a steady state (by driving the same line as before, this time with 100 ct amplitude). Around 2015-08-08 10:18:30 I kicked the TCS power to 0.53 W and started the datataking again.
Once the frequency coupling reached a steady state again, I made a guess for what TCS power we need to minimize the coupling. At 12:43:30 I changed the TCS power to 0.43 W.
I have revered the ALS/CARM cabling to its nominal configuration.
Preliminary analysis from this second run suggests that, of the TCS powers that we probed, our current TCS power is the best in terms of intensity noise coupling.
The attached plot shows the transfer function which takes ISS outer loop PD #1 (in counts) to DCPD A (in milliamps). The coloring of the traces just follows the sequence in which they were taken. Black was taken at 0.23 W of TCS power, and the lightest gray was taken at 0.53 W of TCS power.
The measurements and the plotting script are in evan.hall/Public/Templates/LSC/CARM/FrequencyCouplingAuto/Run2.