[Tanaka, Komori]
Today, we encountered difficulties in the IFO acquisition due to unstable PNC control and frequency kicking of the PRM during PRMI 3F locking.
The instability in PNC control is probably caused by a significant reduction in fringe amplitude, which has dropped below 1000, much lower than the nominal value of above 3000, as shown in klog:30303.
We plan to address and resolve this issue tomorrow by moving picomotors.
We don't have pico motors to align PNC remotely (we have pico motors for green beam but they moves not only reflected beam but also injection beam to the arms),
So, the alignment of PNC is really bad, it is necessary to manually align the optics at POP/POS table.
I'm not so sure the current situation but PNC fringe can be often recovered by just performing initial alignment to recover the GRX/Y alignment.
Just for memo (repeating what I mentioned in this morning): it might be also worth checking what is the green light power at the output of the fiber on the POP table, if the max of the PNC Michelson fringe readout would reduce compared with that of the previous healthy days.
Thank you for your comments, Ushiba-san and Akutsu-san.
We have the small visibility issue in the PNC of GRY.
The GRY trans. power is still around 1.0, so we think the green power at the output of the fiber or the input alighnment of the green have not been degraded.
Therefore, we have a plan to enter the mine to recover the visibility in the afternoon at this moment.
Fig. 1 show the fringe when GR locked with only Y-arm during the lock trial and after the initial alignment in last night. Current, the fringe amplitude is ~1000, this is about smaller than the previous one (~4000) in klog30303.
On the other hand, We also confirmed that PNCX frige. Fig.2 show the fringe when GR locked with only X-arm during the initial alignment in last nigh. In GRX case, the fringe amplitude (~640) seems to be slightly lower than the previous one (~720) in klog29848.
According to the figure attached in previous post, GRY TR NORM fluctuation seems large though GRY TR NORM value seems not so small.
So, please check GRY NORM TRANS fluctuation when GRY PNC fringe was large.
Since GRY NORM value depends on the GRY condition (polarization of GRY fiber output?), it might happen that the GRY alignment becomes bad even though GRY TRANS NORM is close to 1.
Please see klog30234 to know how to perform GRY alignment with PICO motor.
