NAOJ GW Elog Logbook 3.2
Marc and Yuhang
We sent several sine wave to different DOF for filter cavity as following:
| 2Hz | 3Hz | 9Hz | 5Hz |
| Input pitch | Input Yaw | End Pitch | End Yaw |
(At the beginning, 2Hz/3Hz/5Hz/7Hz were used. We will use 7Hz instead of 9Hz in the future.)
By sending these sine waves to different DOF, the check of coupling in reconstruction becomes easier. As shown in the attached figure, we checked many signals before and after excitation. They are:
Oplev signals: Red line: Oplev signal before excitation Green line: Oplev signal after excitation
AA signals: Blue line: AA noise when light goes to QPDs are blocked (actually this is DGS ADC noise) Brown line: AA reconstructed signal before excitation Pink line: AA reconstructed signal after excitation
(AA signal is not calibrated, so it is much larger than oplev signal)
Oplev issues:
Since a large 9Hz peak appears in the oplev signal of End mirror yaw, either End mirror pitch driving or End mirror yaw sensing is strange.
AA issues:
End mirror pitch signal couples to End and Input Yaw.
Input mirror pitch signal couples to End Yaw.
Plan:
1. We are going to check end mirror oplev and coils. 2. Consider to realize a matrix including pitch/yaw coupling
Marc, Yuhang
We went to check to End mirror OpLev : All optics seemed well fixed.
We tuned the beam height to be identical on the injection and detection windows.
We moved vertically the lens on the detection window to have the beam centered.
Unfortunately it didn't change the coupling of pitch to yaw visible in the figure 1 of the parent entry.
We can see that pitch couples to yaw but not yaw to pitch.
This seems to indicate that the sensing matrix of OpLev is not the culprit.
Furthermore, when we inject a line on the End mirror pitch, we can indeed see the beam on the FC transmission camera moving in pitch but not in yaw. Even if the OpLev yaw senses this line...
On input mirror we can see both pitch and yaw lines on pitch and yaw signals from the oplev so it could be solved by finer tuning of the oplev rotation matrix.