A (O. P.): Given the scale of our detector, it is very difficult to reach a very clean environment for chamber production when you work with machined FR-4 honeycomb panels of 1.5m x 3.6m. To solve this problem we developed a special chamber design and technology suitable for mass production which allows to minimize the cleaning procedure and to keep our production operations as clean as possible.
RTV sealing outside of the chamber is maybe not the best solution but it is not the main source of silicon in our detector. The milling of FR-4 skins for making cathode strips and anode artwork potentially is more dangerous for chamber aging because the open (surface ed.) of fiberglass creates a good (opportunity ed.) for silicon etching in CF4-based gas mixture. Probably, the good aging result obtained with our production chambers mostly results from chamber geometry and material. We know that with larger wire diameter and anode cathode gap (more chamber volume, faster gas exchange) the aging effects significantly decreased.

A (O. P.): We tried to control the H₂0 contamination in the gas mixture, but unfortunately did not get reliable data. We estimate the water level to be no more than 200 ppm.

A (O. P.): About 2/3 of the chamber area (~ 1m²) was irradiated during the aging test at GIF (CERN).