Nic, Alexa, Sheila, Evan, Dan
We wanted to measure the crossover between L1 and L3 of ETMY. We took a transfer function from LOCK_L1/L3 to ALS-Y_REFL_SERVO_CTRL_OUT with green locked to the yarm. We found an old template made by Sheila and Stefan for the L1 stage. We repeated the measurement for a few data points (green trace), and it seemed the same as the old measurement (blue) so we aborted the measurement and went with the assumption that it was still a valid measurement. We then measured for the L3 stage (red trace). Clearly the crossover between L1 and L3 is about 2 Hz as expected. Nic plans on dividing these two transfer functions tomorrow morning...
Fo reference the xml file is located here: /ligo/home/sheila.dwyer/ALS/HIFOXY/Y_UIM_2.xml
Here is the ratio of the ETMY UIM and ESD actuator gains (red and blue traces in original post).
It looks like our crossover is about 2Hz and the phase margin is about 45 degrees.