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Successful demonstration of a new superconducting RF cavity design with beam


In cooperation with GSI, physicists and engineers from the Helmholtz Institute Mainz and the Goethe University Frankfurt have performed the first successful test of the novel design of crossbar (CH) superconducting RF cavity with beam. This is one of the main milestones for the proposed superconducting continuous wave (cw) linac, which can open up new research opportunities at GSI and FAIR with its a continuous beam of particles. Among other things, this makes the accelerator particularly well suited for the creation of new chemical elements.

The cw-linac demonstrator that consists of one CH-cavity was studied with beam for the first time in June and July 2017, using a beam of heavy ions at a test facility of GSI Helmholtzzentrum für Schwerionenforschung. In this test, argon ions were injected into this innovative system and accelerated. “The continuous wave linac demonstrator achieved full particle transmission and reached the target beam energy,” says Dr. Winfried Barth, who heads the cw-linac development team. “The cw-linac demonstrator used an acceleration voltage of 1.6 megavolts to accelerate a heavy-ion beam with an intensity of 1.5 particle microamperes to the target energy over a distance of just 70 cm,” said Barth, describing the success of the test. The result confirms the effectiveness and capabilities of the novel design of CH-cavity, whose development was largely funded by the Helmholtz Institute Mainz through the Acceleraor R&D programme "Matter and Technologies" by the Helmholtz Association.

Because the proposed cw-linac is to generate a continuous beam of particles, it is particularly useful for the creation and examination of super-heavy elements, which is one of the traditional fields of research at GSI, the Helmholtz Institute Mainz, and the Johannes Gutenberg University Mainz. At GSI, scientists have discovered a total of six new elements and investigated their chemical and physical properties. The proposed cw-linac’s continuous beam will not only benefit the heavy element programme, but also experiments in the field of materials research.

“A normally conducting accelerator would have to be much longer than the proposed superconducting cw-linac. Moreover, it would need huge amounts of energy to create such strong electromagnetic fields and it would also have to be strongly cooled,” says Dr. Florian Dziuba, who designed, developed, and commissioned the CH-cavity, a radio-frequency accelerator structure that is the key component of the continuous wave linac. Dziuba performed this work as part of his doctoral thesis at Goethe University in Frankfurt.

Because of its compact structure, the superconducting continuous wave linac will be able to save space and conserve considerable amounts of resources in the future. The linac is expected to accelerate ions to as much as 10% of the speed of light over a distance of 13 meters. “The system’s multicellular structure, which is being used here for the first time, is the most complex superconducting radio-frequency structure to have ever been built for use with an ion beam,” says Dziuba, who is now employed at the Helmholtz Institute Mainz.

The current test module of the cw-linac is approximately 2.20 m long and has a diameter of 1.10 m. In order to become superconducting, the accelerator’s interior, which is made of niobium, is cooled down to -269°C. “The fact that the demonstrator achieves the expected performance is a big success for the whole team and shows that the new design of the CH-cavity is groundbreaking”, says Barth.

About the Helmholtz Institute Mainz

GSI Helmholtzzentrum für Schwerionenforschung (GSI), Darmstadt, and Johannes Gutenberg University (JGU), Mainz, jointly established the Helmholtz Institute Mainz (HIM) in 2009 in order to further strengthen their partnership, which has existed for many years. At its location in Mainz, the HIM conducts experiments and theoretical investigations concerning the structure, symmetry, and stability of matter and antimatter. The institute receives its basic funding from the German federal government and the state of Rhineland-Palatinate. JGU supports the HIM by providing it with infrastructure.

The cw-linac demonstrator and the development team.
View inside the cw-linac.
The superconducting cw-linac produces a continuos particle beam.
from left: Maksym Miski-Oglu, Winfried Barth, Alexander Schnaase, Stephan Yaramyshev, Victor Gettmann, Manuel Heilmann, Florian Dziuba
Photo: Gabi Otto/GSI Helmholtzzentrum für Schwerionenforschung GmbH
Photo: F. Dziuba/Helmholtz Institut Mainz
Photo: Gabi Otto/GSI Helmholtzzentrum für Schwerionenforschung GmbH