HELIAC linear accelerator progresses: Cryomodule tested


The HElmholtz LInear ACcelerator HELIAC is a continuous-wave linear accelerator planned at GSI/FAIR that opens up new research opportunities with its continuous particle beam. The first cryogenic accelerator module for HELIAC, the so-called Advanced Demonstrator, has now been cooled down to four Kelvin with liquid helium and tested.

The cryostat of the HELIAC demonstrator has a length of five meters in total. In the future, it will contain three accelerator cavities of Crossbar H-mode (CH) type, as well as a beam focusing cavity (buncher). These components are still being tested or manufactured. This is why, for now, externally identical dummy cavities were installed, which do not contain the internal structures. They are used to ascertain the mechanical behavior of the module under cooling. Two finalized solenoid lenses and two steering elements — both superconducting — are already installed.

For the first time, the demonstrator has now been successfully cooled down to four Kelvin using liquid helium from the GSI magnet test facility. The superconducting solenoid lenses were used to focus heavy ion beams from the GSI high-charge injector through the cryomodule and keep them on axis using correction coils.

“Thus, all relevant transverse beam optical investigations could already be successfully performed with the setup. This means that an important milestone in the commissioning of the module has been achieved,” explains Professor Winfried Barth, head of the Section 1 for Accelerators and Integrated Detectors at the Helmholtz Institute Mainz and, at the same time, head of the GSI “Linac” department. The Helmholtz Institute Mainz, a branch of GSI, is responsible for all R&D-activities in order to realize the HELIAC project.

“Shortly, the Advanced Demonstrator will be transported to the Superconducting Radio Frequency Laboratory of the Helmholtz Institute in Mainz, which provides unique manufacturing infrastructure and the high-purity conditions for the final assembly of the cryogenic module,” adds his deputy and HELIAC project manager Dr. Maksym Miski-Oglu. “The next step there will be to integrate the three functional CH cavities and the buncher into the cryomodule. Final commissioning with heavy-ion beam is planned for mid-2022 at GSI/FAIR.”

The HELIAC CH-cavities, which are also superconducting, can accelerate heavy ions with high efficiency. Because of its continuous-wave mode of operation, the setup is also known as a cw linac. Several experimental areas shall benefit from the continuous particle beam in the future, such as superheavy elements research and materials research. (CP)