NAOJ GW Elog Logbook 3.2
Marc, Michael
Because we are missing some SR560 now to check the input oplev we decided to check the end ones.
We recentered the beam on the PSD and confirmed the good condition by measuring the usual spectrum of the END oplev for pitch and yaw.
We tried to measure the TF between END mirror yaw excitation end the 3 dofs of the oplev.
However, we did not manage to have coherence about 0.1 between yaw excitation and yaw signal from the oplev.
We checked the coils and they are working fine.
We injected white noise from about 500 to 4000 counts amplitude but it did not change the coherence value.
We will try to check with excitation over longer duration.
We also tried to realign the length PSD but could not find proper values from MEDM.
We will try again this alignment removing the SR560 to avoid too large gain of the signal.
Marc, Michael
We checked the END oplev SR560 and found out that the length oplev one was saturating.
We decreased the gain of all down to 1 and realigned all signals. After that we increased the gain back to 100.
For reference, the tilt PSD sum is about 4500 counts and shift PSD sum is about 3000 counts.
Marc, Matteo, Michael
One possible reason for our very low coherence could be that we injected uniform noise with 4000 counts.
To improve both the driving and sensing it is actually better to inject noise through swept sine.
We did so with noise amplitude of 10000 counts and found that the length mechanical resonance at 0.9 Hz was strongly excited in every dof.
Either the noise is too strong, the PSD is at a wrong position or the driving matrix needs to be tweaked.
We are currently taking again this measurement with lower noise amplitude at 4000 counts.