Repairing the east arm vacuum system
On June 28, 2021, the GEO600 team worked with a vacuum welding contractor to repair one part of the GEO600 vacuum system, which has now been in service for more than 23 years. While the focus in October 2019 was on the north arm of GEO600, the work now concerned the east arm. In addition, the leaks to be welded were fortunately hidden behind flanges as they were several orders of magnitude larger than the tiny leak (0.1 mm) in the north arm. Prior to repair, the team filled the vacuum in the east arm to atmospheric pressure with high-purity nitrogen. This step avoids contamination and allowed a very low vacuum pressure and thus measurement operation to be restored as quickly as possible. As a result, data acquisition could be resumed on July 8, 2021.