I have updated the green beam references. Next time when the interferometer drops the lock, we should run initial alignment from scratch.

[Overview]

I have updated the green beam references (ALS-X/Y_QPD_PIT/YAW_OFFSET and ALS-X/Y_CAM_ITM_PIT/YAW_OFS) this after noon in response to alog 31873. We didn't try locking the interferometer with this new set of references yet, but theoretically this will give us smoother locking sequence (e.g., less fluctuation in the power recycling gain and etc.). The adjustment was done with the interferometer fully locked on DC readout with an input light power of 2 W.

[Automation scripts]

This time Sheila suggested making an automation script so that we don't have to repeat this process by hand in future. So I made such scripts which are attached to this entry. These scripts servo the QPD offset points by looking at the green WFS error signals. The servos are based on the cdsutils.servo module and the servos are activated only when the green transmission signals are sufficiently high. The input matrices I chose are very naive (they are a diagonal matrix) but were good enough for individual loops to converge slowly. I didn't really try to adjust the gains yet, but probably one can bump up the servo gains if things are too slow. One trick that I re-discovered (and Sheila told me) was that the Y arm WFSs have a local minimum where the WFS error signals can go close to zero while the green transmission is not high. I am not sure if the script can handle the servos if the misalignment is too large. Today, in fact, I initially fell into this local minimum. I manually brought the QPD offsets to a point where the WFSs are not far away from zero and the transmission is high-ish. Then I adjusted the input matrix and gain there in the script which ran OK afterwards. I didn't have any troubles for the X arm.