The vacuum leak causes problems yet again
On December 17, 2018, once again luckily during regular working hours the vacuum leak which was temporarily closed in August 2017 opened again. The vacuum glue Tra-Bond (blue layer in the image above) used as a temporary seal had become brittle and was loosely lying on the vacuum tube.
Again, the situation was critical, and again the team managed to solve the problem quickly. It became more and more clear that the use of glue was not a permanent solution, but the only one available for the time being.
Discussion after the second serious incident led to the decision that the leak would have to be welded after the area around was thoroughly cleaned. Properly welding would however require bringing the inside of the vacuum tube to slightly above ambient pressure. This would need to be done with a high-purity inert gas to avoid any contamination and months of pumping back to 10-9 mbar afterwards.