Hi,
many, many thanks for all of the comments.
Summarizing all ideas I believe to know the answer: simply an iced helium fill port.
Of course, for the moment that's just speculation and the source of the ice by no means is clear, because the helium dewar always is slightly overpressurized.
Next Monday an engineer will have a look inside the magnet. After that inspection I will provide a more extensive summary.
Once again many thanks.
Rainer
Received on Wed Feb 12 2014 - 10:11:40 MST