[Ushiba, Nakano, Kokeyama]
Data of the precision particle counter was take and plotted, see the attached plots. Data from Jun 19th to 27th is plotted. It's ISO class 3. There is no obvious tendency of cleanness degradation over ~8 days.
There is one huge peak at around 16:47 JST on June 26th (Did anyone go inside? - even if so, it's a massive count.) The second plot is the data excluding this huge jump. Overall, there is no tendency of the degradation. The first data point is probably due to the residual particle inside the air sampling tube.
We kept the particle counter running in the PSL room.
PSL Koach turned on for the cleanness test, on 6/28 Fri 12:53 JST
Here is the result of the particle counts when Koach filters were on when we tested on June 28 (indicated by an arrow in the first figure). With Koaches, the cleanness immediately became extremely good, iso class 1. When Koaches were off, even with all doors closed, the clean level degraded to something like iso class 3.
Not sure [No Koaches, iso class 3] is enough good or not, especially for the high power operation.
The second figure is the data from July 1-2. The cleanness degraded drastically in the last several hours for some reason (someone entered the room without turning on Koaches?) I feel worrysome for the high power operation...
