[Aritomi, Michael, Yuhang]

Today CC2 mass feedback was very unstable with gain of 2.7. We found that coil output to input mass was too large, so Yuhang offloaded the input mass with picomotor. After that, CC2 mass feedback becomes stable with gain of 2.7.

We tried to figure out the cause of 100Hz bump and found that the glitch appeared in CCFC error signal when we touched the SMA cable for CC1 mixer. We tightened it.

Then we measured FDS with CCFC (Fig 1). The degradation parameters are same as elog2597. The 100Hz bump maybe a bit better, but still present... The detuning fluctuation is ~20Hz. I noticed that the detuning seems anti-correlated to the homodyne angle.

To determine the squeezing level and generated squeezing precisely, I measured the shot noise and nonlinear gain just after the FDS measurement. The p pol PLL frequency for 20mW was 185MHz and BAB maximum was 282mV with 16mW power meter range. The BAB maximum without green is 56.8mV with 240MHz of p pol PLL frequency. This means the nonlinear gain is 5, which corresponds to the generated squeezing of 10.8dB.

For precise degradation budget, it is very important to measure the shot noise and nonlinear gain just after (before) the FDS measurement.