Michael and Yuhang

Today, we investigated various signal and noise level from CCFC PD. In addition, the servo noise is also added to be compared with signal level.

Attached figure shows their comparison. There are two signals measured in the figure. One comes from picking off signal with beam sampler(~1%), the other comes from BSN11(~3%). The splitting ratio was measured with power meter (offset has been subtracted).

From this measurement, BSN11 would be suitable for the signal pick-off. By using this signal, probably a bandwidth of ~50Hz could be achieved without reinjecting noise. We will try to lock FC with BSN11.