Ring closure for large FAIR accelerator: structural work is completed


It is a central part of the future accelerator center FAIR, currently being built in international collaboration at the GSI Helmholtzzentrum in Darmstadt, and at the same time the heart of one of the largest construction projects for research worldwide: the large underground FAIR ring accelerator SIS100 on the northern FAIR construction site with a circumference of 1,100 meters. On the same place where the groundbreaking ceremony was held a few years ago, representing the start of the building and civil engineering works, a decisive step has now been reached: The structural work for the SIS100 is completed. The ring closure of the tunnel system has been made, and the concrete layer of the last tunnel slab has been poured. The ring closure marks an important milestone in the realization process of the entire FAIR project.

The large ring tunnel consists of the two tunnel areas running next to each other, one for the accelerator machine and the other for the corresponding technical and supply facilities. The base lies at a depth of 18 meter. The ring tunnel for the accelerator was built in several segments, each about 25 meters long. After the completion of the load-bearing parts, the ground slabs, walls and ceiling structure, the assembly of the technical building equipment (TGA) such as electrical supply, air-conditioning technology, safety technology etc. is upcoming. The excavation pit will now be backfilled progressively, and additional storage and lay-down areas for the TGA companies will be prepared above ground. After the last slab has been concreted, a logistics opening is still being kept open so that the majority of the formwork for the tunnel can be lifted through. Later, it will also be closed.

SIS100 is a project of superlatives, which is also reflected in some key data: In the northern excavation pit, with its underground ring accelerator as the central building structure, almost one million cubic meters of earth were excavated for construction, to a large part it will be backfilled on site. Around 159,000 cubic meters of concrete were used for the SIS100 accelerator ring, and 27,000 tons of steel ensure the reliable stability of the underground structure.

The Technical Managing Director of GSI and FAIR, Jörg Blaurock, was pleased with the completion of this stage, which is so important for the entire FAIR project: “FAIR is a scientifically and technically extraordinary construction project. It requires customized solutions, and numerous individual trades have to mesh. Therefore, structural and civil engineering, accelerator development and construction, and the scientific experiments are closely coordinated in our integrated overall planning. The recent ring closure is the result of precise planning and implementation and a substantial progress for the entire project. The close interlocking and integrated coordination with all parties and stakeholders involved is a decisive milestone of the realization strategy for the FAIR project”. (BP)