Daniel, Nutsinee

Today we installed a phase frequency discriminator chassis (U7 on SQZ rack near ISCT6). The pump/PSL beat note RF signal and 158MHz LO went in and the output went to OPO common mode board. We unplugged the PZT output and only used the fast path error signal to feed into the 158MHz VCO. The 158MHz VCO now follows the beat note frequency. Here's a quick look at the control signal. More noise hunting+modeling is required to be able to pinpoint where all of them came from. We suspect temperature to be responsible for low frequency noise.

Sadly locking at 0 Hz beat note doesn't mean high 3MHz peak when using PSL LO. A feed forward from IMC land is required. A model has been modified to sum the OPO fast control signal with this feed forward signal and the output will go to the OPO PZT somehow (don't remember what we decided on). Once this is complete then we can work on the 3MHz hand-off.