Two vacuum vessels ATLAS
Based on a design by Rutherford Appleton Laboratory (RAL), UK, Schelde Exotech manufactured under a NIKHEF contract two 500 m3 large vacuum vessels for the cryostats of the ATLAS End Cap Toroids.
These 11 meter diameter castellated aluminum vessels with stainless steel bore tube, are essentially made of 40 mm thick plates for the shells, 75 mm thick plates for the end plates and 150 mm thick bars for the flanges, all bent, machined and integrated by MIG welding. The closure of the flanges takes place by means of dowels and bolts with double O-ring seals. Because of transport constraints, the vessels were made in halves, temporarily sealed and vacuum-tested at the works, and then transported to CERN for final assembly and acceptance tests. Despite the large size of the vessels, the requested very tight geometrical tolerances were achieved by good control of the welding process, the development of adequate jigs and fixtures, and the use of stress release. Both vessels were vacuum-tight and the meticulous and clean way of working ensured that a high vacuum was obtained within a few days of pumping. The delivery to CERN was completed in July 2002.
With the experience of welding thick aluminum, Schelde Exotech also gained the order for manufacturing the BT-coils for ATLAS. These coils are welded from 200 mm thick aluminum and the total construction has a length of 25 meters and height of 5 meters. Because of the high tolerances needed for machining, these coils were welded according a strict welding regime and stress relieved. 16 Coils were fabricated and now form part of the ATLAS experiment.