--

1. AOM switching

We suspected that the AOM for the ISS introduces the phase noise. I measured the IMC control signal with/without the AOM, but there is no difference 

 

2. Laser reset

We turned the current to the laser crystal of the two Prometheus off to reset them. It did not change anything.

However, actually, we should turn the power of the laser interface off, not only the current. We will check it tomorrow.

 

3. VCO reference signal check

We reset and check the waveform of the reference signal of the VCO for the Gr-PDHs. It seemed fine.

 

4. LAN cable of the FG disconnection 

I disconnected the LAN cable of the function generator for the PLL LO. I suspected that the supervisor for the remote control doing something, but it does not seem to.

 

5. Intensity noise investigation

I checked the intensity noise of the injection laser into the cavity. We already checked if the input and transmitted laser power have coherence or not. Although they don't have a coherence yesterday, they do have today as shown in the attached figure. Actually I found that the laser power fluctuation has a time dependence shown in the second time series plot. 

Also, I found that the spectrum of the laser intensity fluctuation of GRX gets larger when the shutter is open and ITM is aligned. We cannot see previous data, since klog11406, so we don't know if it was like this before the current problem happened. I will check the intensity noise in the PSL tomorrow and find the reason.