KAGRA Logbook

Reports 1-1 of 1

VIS (EY)

takafumi.ushiba - 17:07 Friday 19 January 2018 (3990)

Realignment of the main beam from ETMY to BS

[Ushiba, Miyamoto, Izumi]

We realigned the ETMY for returning the beam to the BS by using the same method in 3876.
Since the laser power becomes roghly 8 times larger than that of the time of 3876, the expected output of the PD put near the BS is 48,000 counts.
But the maximum calue we measured is about 15,000.
We have not confirmed the reason yet.

During this realignment, the OpLev signal could not be the refeerence of the alignment because the screws of the OpLev optics were very loose and they could easily move.
After the realignment work, we tightened the screws of the OpLev optics.
So, we can probably use the OpLev signal as a reference of the ETMY alignment now.

Comments to this report:

tomotada.akutsu - 21:39 Friday 19 January 2018 (3992)

And after the works Ushiba-kun reported, Izumi-kun and I entered again the tunnel to check whether the transmitter side would be loosen or not; was slightly loosen, and so we tightened them upwith monitoring the oplev output, and during the work pitch was slightly shifted from zero-centering, and so we roughly zeroed the pitch again by moving the QPD.

In my verrrry small memory someone guy reported me that the plan was that the tightening of the QPD should be done after the alignment (not meaning the "re-alignement" this time) of ETMY so that it can once reflect back laser beam to BS in December had been done, but I guesstimate the plan was not shared or just forgotton...

Anyway, please don't hesitate to check every part of the setup fixed rigid before you leave your oplev as a reference.

Hopefully checking by several experts independently would make the situation assured.