[Michimura, Akutsu]

The collimator holder fot the EXA's oplev has been exchanged to thorlabs. Then the direction of the light source has been aligned so that the beam can enter the QPD. And then we have had the oplev beam center by using the actuators on the QPD stage. This work was done without the interferometer's main beam.

By the way, the QPD's surface seemed dirty, and some of them seemed glass flgaments. I think this comes from the viewport broken, which had happend on 3/14 ([kagra-pms 02950]). Anyway, we took the picture and wipe the surface with ethanol gentely.

We also found the oplve viewport's surface facing the QPD seemed dirty (not by glass but dusts), and wiped out them with ethanol gently. The surface of the oplev viewports has an AR coating, so usually wiping is not recommended. A scar-like thing can be seen in Fig. 3, (and we got surprised a little bit), but it can be wiped out in Fig. 4. Anyway the clean booth would be dusty.