Yuta, Tomo, Masayuki, Lucia, Kiwamu,
We continued working for getting more stable lock of the X green laser to the X arm today.
As reported in 6670, now the ITMX model runs at 2 kHz which should give us smaller number of DAC glitches. In addition, the tidal path (6666) has been commissioned today and is now a part of the guardian automation. However, since the ETMX mirror keeps oscillating at 0.7-ish Hz, this prevents us from achieving 2 hour lock. This needs to be investigated tomorrow. We are leaving the X arm PDH guardian running so that it is going to keep trying to lock the X green laser to the X arm allthrough the night.
By the way, the attached is a measured spectrum of ALS noise that we obtained today. The green trace is calibrated free running noise spectrum of the X green laser frequency compared against the X arm displacement when the X green laser is locked to the X arm. The y-axis is frequency noise for 1064nm calibrated in Hz/Hz1/2. The calibration was done by taking the feedback signal and multiplying a factor of 0.43 MHz/V (6544) to it with the assumption that the ALS PDH loop has infinite gain in the frequency band. The red trace is an estimation of the frequency noise of the main laser by Nakano-kun based on his control model.
