European Spallation Source, ESS
The accelerator of the European Spallation Source (ESS) in Lund, currently being built, includes a section with 26 superconducting double spoke resonators, also called spoke cavities, that accelerate a proton beam from 90 to 216 MeV. This type of superconducting cavity has never before been used in an accelerator. FREIA assists in the development and testing of these cavities to prepare for the construction and operation of ESS.
FREIA has a dedicated test facility for studying the performance of superconducting accelerating cavities. It is used to measure, at low and high power, the performance of double spoke cavities for the ESS linear accelerator (linac) and decide on their installation. Complete cryomodule systems consisting of a cryostat with two superconducting cavities, frequency tuning control and radio-frequency high power amplifiers and controllers will be evaluated to measure the system performance. The project focuses on the development of high power radio-frequency generation and control technology, and development of superconducting spoke cavities and their application in particle accelerators.
In 2017 FREIA successfully tested one of this double spoke cavities equipped with cold tuning system and fundamental power coupler.
The next step was then to test these cavities in the same configuration as they go into the accelerator, which means two cavities, each one fully equipped with a cold tuning system and a fundamental power coupler, inside their own cryostat or cryomodule. In 2019 FREIA tested a prototype cryomodule, which lay the grounds for the series testing of the cryomodules that will be part of the accelerator. With a total of thirteen cryomodules to be tested, FREIA has already started this project in 2020 and will continue throughout 2021.