The contamination control inside the lower part of the tower has been performed (as usual) with the surface particle counter in three steps:

1. as soon as opened the tower (Tower opening),
2. after the interventions (payload dismounting and dummy payload installation/removal),
3. as soon as cleaned with CO2 machine and isopropyl alcohol (Cleaning cycle).

Further measurements will be performed after the planned vaccum cycle.

In the attached figure the results of the measurements.

More details for the measurements in the other towers at: https://apps.virgo-gw.eu/dust/