Hirata, Takano, Aso

Ultra-pure water generation

A new ultra-pure water was delivered. So we set it up.

The new ultra-pure-water generator does not have a purity sensor. So we connected the output of the generator to the purity sensor of the old generator to check the purity of the water.

We were able to achieve up to 16MOhm (on average 15MOhm or so).
More than 17MOhm is considered ultra-pure water, but 15MOhm is still pretty good.

We cleaned a stainless steel cup. Then we poured the ultra-pure water to the cup, let it overflow for about an hour to clean the cup.
After that, we filled the cup half full with the ultra-pure water and put a cap on the cup with aluminum foil to transport the water to the PR3 clean booth.

Mirror cleaning

As a preparation, we put a protection jig used for the first contact application on PR3 HR side.
This jig is used to catch the water blown away by the ion gun.
Cleaning of the mirror was done in the following steps:

1. Identify a stain on the mirror with an inspection light
2. Soak a clean swab with ultra-pure water
3. Lightly tap on the stain with the swab
4. Blow away the water drops on the mirror surface with an ion gun.

Vide of the cleaning work
https://photos.app.goo.gl/6AoRwzKn7LSTT4XA8

Some of the stains were removed in this way. However, most of the stains, especially small dot like ones, could not be removed with the above method.
Therefore, we abondoned the cleaning with ultra-pure water.
The PR3 HR side looks like below at the end of today's work. A lot of small stains are visible.