Tomo, Masayuki, Kiwamu,

The ETMX pitch situation has improved somewhat tonight. However, since the PSL is not in a good shape, we don't expect a long lock stretch.

Here is a summary of the locking status tonight:

• The 0.7 Hz (more accurately it was 0.78 Hz) oscillation is better tonight.
  • This could be due to our effort of changing the IP position and the vertical height (6707). We think that the vertical height was the one which improved the situation.
  • The ETMX pitch went down below a urad tonight. Good.
• However, instead, a peak at 0.685 Hz dominated the rms in pitch in ETMX.
  • This peaks seems a very high Q and we needed to wait for an hour to two to decay to a level where we can start locking.
• We intentionally kept the IMC unlocked because we had a problem with the MZI locking which disturbed the IMC locking.
• As a consequence the noise of the X green PDH changed from the last night significantly.
  • This noise should represent the performance of the main laser stability with the reference cavity only.

Attachment1: Noise spectra of the ETMX optical lever tonight. The peak at 0.78 Hz was not an issue tonight but 0.625 Hz was the dominant for some reason.

Attachment 2: Unsuppressed frequency noise as seen by the ALS PDH X. The spectral shape is different tonight because we didn't have the IMC locked due to an issue with the MZI. We used the same calibration technique as described in 6678.