The European Spallation Source is an international, multi-disciplinary research facility based on the world’s most powerful neutron source. It is currently under construction in the city of Lund in southern Sweden. RI won the production of 88 high beta cavities for the ESS, to be delivered as in-kind contribution of UK Research and Innovation UKRI, formerly known as STFC Daresbury.
UKRI ordered the production of 88 superconducting 704 MHz 5-cell cavities from RI. The contract is split into a pre-production and test of 4 first article cavities and the production of the remaining 84 series cavities. The cavities will be produced from niobium sheet material provided by UKRI. After fabrication the cavities will receive the final surface preparation at RI and will be shipped to UKRI under vacuum and “ready for cold RF testing”. The surface preparation of the cavities includes removal of the inner cavity surface by buffered chemical polishing, a 600°C vacuum annealing, high pressure water rinsing, clean room assembly with RF antennas and flanges, and the welding of the titanium helium vessel to the cavities.
This cavity production project is an ideal follow up project using the RI infrastructure that was set up at RI for the production of 420 1.3 GHz 9-cell cavities for European XFEL between 2010 and 2015, and which was also used for the production of more than 200 1.3 GHz 9-cell cavities produced for the LCLS-II project at SLAC in California, which ends in 2018. Only minor modifications of the RI facilities will be necessary to allow the surface treatment of the somewhat larger and heavier 704 MHz high beta cavities for ESS. Within the last year RI already produced 5 almost identical cavities for CEA in France, which will be used by CEA for assembly into the prototype ESS high beta cryomodule.
The production of the 88 ESS high beta cavities will take until the middle of 2020 with a series delivery rate of 8 cavities per months. The project will ensure smooth continuation of our SRF business and give a good work load for our engineers and especially our manufacturing specialists. In parallel to the ESS cavities, RI has received other cavity orders that will ensure a production of substantially more than 100 cavities per year for the next years.