The Cleanrooms of GEO600
The handling of high quality optics requires cleanroom facilities to prevent even microscopic dust particles from entering the system. These dust particles would eventually be attached to the mirror surface and burnt into by the intense laser radiation of about 3 kW/cm2. As the handling of the high quality optics naturally takes place in the vicinity of and even in the tanks at least the surroundings of the tanks have to be of cleanroom quality. We hope to achieve a class <100 cleanroom (during the time a tank is opened) with the help of mobile plastic tents forming a laminar-flow box, large enough to enclose the tank and one or two people working with the optics.
The next section of cleanroom (worse in its quality) will be formed by the major part of the building itself. The "tank section" of the building will be separated from the platform section by some kind of transparent plastics sheets of some mm thickness, indicated by the shaded areas in the picture below. This shiedling will be sealed airtight. Pressurizing the inner part to a pressure by about 0.1 mbar higher than the "platform section" will keep dust from entering the "tank section". The tank section must not be entered without proper cleanroom clothings. The platform section will contain computers, electronics, and most of the stuff needed for daily tasks. The platform section will also serve as a "viewing point" for visitors. This section may be entered with ordinary clothing. In front of the building (not shown in the picture below) we will place a container that keeps all the really dirty stuff. Rubber boots, bikes, the new jacket you spoiled when you slipped and dived into the mud on your way from the east end-house..., have to be put off in this container before you may enter the platform section.
The corner of the central building where the pumps are placed (i.e. the part below the platform in the back part) will also be seperated from the tank section. We consider the pumps as too dirty and noisy as to be allowed in the same room as the tanks. Access to the pump room will not only be possible through a door at the floor level but also through a man hole from the platform atop of the pump room. This avoids that we have to cross the cleanroom to get to the pumps. The major part of the vacuum system can be remotely controlled anyway.
Cleanroom performance of the end houses will be achieved in a similar way.
