With Uchiyama-san,

Summary

We checked the Pcal-Y alignment and found it was changed.
Then, we recovered it roughly: the ETM reflected beams can be observed at EYA.

Details

We checked the alignment of Pcal-Y, then found that the alignment had been significantly changed. (10-15cm of beam position shift at the output of EYA chamber = bellows position for path 1, and at the MPL4 point for path 2.)
The cause of this is unknown. (It could be due to Tx work prior to discovery of the oil, or it could be due to EYA cleaning.)

We tried to recover the alignments and succeeded in making the ETM reflected beams back to EYA.
We touched all mirrors before ETM, except MP1 for the recovery.
The attached pictures were taken after the alignment adjustment.

We will remove the mirrors tomorrow and start cleaning.

Date: 2024/6/5

With Ikeda-san

Summary

We removed most of the mirrors in EYA chamber for cleaning.
We cleaned 3 mirrors today. The most effective method is to use ultra-pure water with the drag washing method.

Details

1. We removed all mirrors in EYA chamber except MP1 and MP8, and carried them to the draft chamber area at the center.
2. Check the mirror contamination -> it seems there are 2 kind of contaminations: one (type A) is a small dot-like contamination, the other (type B) is a large drip-like contamination. The former were many, on most mirrors, and the latter were several on most mirrors.
3. Cleaning of the 1st mirror = MPL3
   1. No type B contamination on this mirror.
   2. At first, we used ethanol with the drag washing method. -> It had little effect.
   3. Next, we used acetone with the same method. -> It had little effect.
   4. Finally, we used ultra-pure water with the same method -> Very effect on type A. Most of the type A contaminations were removed with the first wipe.
   5. Wiping with deionized water was performed three times.
4. Cleaning of the 2nd mirror = MPU3
   1. From the beginning, we used the ultra-pure water. -> Similarly to the above, there was a significant effect.
   2. We finished cleaning this mirror with 4 rounds of the ultra-pure water wipes.
   3. Type B contamination was only one and very small on this mirror.
5. Cleaning of the 3rd mirror = MP2
   1. This mirror is one of the 4-in mirrors.
   2. 3 rounds of the ultra-pure water wipes made most the type A contaminations clean.
   3. 3 rounds of ethanol and 6 rounds of aceton wipes made the type B contaminations almost clean. We still can recognize them with a very powerful green light.

With Yuzurihara-san and Takase-san

Summary

We cleaned all the remaining mirrors.
There was a small amount of contamination that could not be removed, but should have little impact.
After this work, we fixed all mirrors on their mount.

I attached before/after pictures of each mirror.