A new Cryomodule is being developed at KEK to demonstrate high acceleration specification performance, as required for the International Linear Collider (ILC). This project, funded by a grant from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), will last five years, starting in 2023. The cryomodule in development is built on the ILC design but has been updated to include the latest technology.
The cryomodule is equipped with superconducting radio frequency (SRF) cavities inside and keeps them extremely cold, allowing it to accelerate particles efficiently. These cavities need to be at -271°C to become superconducting, which minimises energy loss during particle acceleration. The cryomodule achieves this by using liquid helium to cool the cavities inside an insulated tube.
KEK has been developing accelerators for the ILC, including the STF-2 accelerator, which comprises 14 L-band 9-cell superconducting cavities. However, the ILC requires that all countries develop accelerators according to standard specifications. For this reason, the cryomodule design specified in the Technical Design Report is now being developed in accordance with standard specifications worldwide.
The following technological developments are required in this project;
- Development of superconducting cavities with high acceleration gradients, in compliance with the Japanese High-Pressure Gas Safety Act
- Design and prototyping of high-performance cryomodules, incorporating the latest technology.
Research institutes outside Japan are also involved in this effort under an international framework called the ILC Technology Network (ITN). CERN and KEK agreed in July 2023 to collaborate under the ITN framework, and this work is being conducted under the ITN framework. For instance, in collaboration with CERN and other organisations such as CEA (France) and INFN (Italy), efforts are being made to produce European superconducting cavities. Since superconducting accelerators require cooling with liquid helium, compliance with the High-Pressure Gas Safety Act is essential. This marks one of the initial efforts and a significant challenge to producing a superconducting cavity abroad that adheres to the High-Pressure Gas Safety Act in Japan, as well as to install intoa cryomodule. Korea University in South Korea is also working on developing a cavities that meets ILC specifications.
The cryomodule features peripheral components like input couplers and frequency tuners. Notably, it incorporates cutting-edge technologies being adopted for the first time in Japan, such as cylindrical ceramics for couplers. We are collaborating on these advancements with researchers from DESY in Germany, the Irène Joliot-Curie Laboratory of Physics of the Two Infinities (IJCLab) in France, and the Fermi National Accelerator Laboratory (Fermilab) in the USA.
At present, young researchers from KEK iCASA’s SRF Group are at the forefront of cryomodule development. Notably, this is their first experience with designing and manufacturing a cryomodule. They are engaging in active research, independent thinking, and deepening their understanding, providing an excellent chance for skill development and learning.
The cryomodule is expected to be finished and its performance assessed by the end of 2027. Scientists are united in these efforts, working together with researchers worldwide to achieve positive results.
It will be appreciated to include some comment on the effort for our cooperative work and agreements with European XFEL program, and with the the US-Japan Science cooperation including the LCLS-II program. Further suggestion has been sent to the editor.