Yuhang, Michael

From 2023-12-29

We felt the squeezing (CC1 error signal when scanned) was too low, so we decided to realign alignment mode cleaner (i.e. realign infrared to homodyne). The alignment mode cleaner can have some backlash if adjusted over a large range too quickly, i.e. if the system is out of use for a long time. The LO was a bit misaligned, and BAB was very misaligned with about a 10% mode mismatch appearing since the last alignment a few days ago.

We then saw that CC2 has some issue with a quite fast oscillation in the error signal (when scanning, it should be going slowly up and down on a timescale of about 0.5s). It turns out I accidentally put the AMC scan signal (1V 10Hz) into the CC2 phase scan for data taking (should be 10 mV 0.01 Hz). Apparently this misaligned the green phase shifter (before GRMC) quite a lot, and the GRPS PZT had some hysterisis and didn't recover properly.

Otherwise, LO and BAB alignment were individually fine afterwards.