Magnets for FAIR ring accelerator: Commissioning of new test facility in Salerno, Italy


The future FAIR ring accelerator SIS100 uses superconducting magnets for deflection, focusing and correction of the circulating ion beams. While the complete series of dipole modules required for beam deflection has already been manufactured and tested, series production of the quadrupole modules required for focusing and correction is still in an earlier phase. In the meantime, an important step has been taken with the commissioning of the cryogenic test facility THOR (= "Test in Horizontal") for this magnet group in Salerno, Italy.

On the occasion of the successful commissioning and to agree on important aspects of further collaboration, a delegation of GSI/FAIR, consisting of the Scientific Managing Director Professor Paolo Giubellino and the Technical Managing Director Jörg Blaurock as well as staff members of the SIS100/SIS18 subproject, visited the facility in Salerno. Also on site were representatives of the management of the Italian National Nuclear Physics Institute (INFN, Istituto Nazionale di Fisica Nucleare), where the test facility is assigned. The visit also included a meeting with the management of the University of Salerno, which, among other things, provides laboratory space and technical support for the development of the equipment.

The quadrupole modules for the FAIR ring accelerator are extremely complex. Key components are the superconducting quadrupole units. Each module contains two quadrupole units as well as other, technically highly sophisticated components. These include, for example, the thin-walled magnetic chambers cooled with liquid helium, the cryogenic ion catchers and the cryogenic beam position monitors. The value chain, i.e., the manufacturing stages of SIS100 quadrupole module production, thus includes numerous suppliers and locations. After production, the superconducting quadrupole units are sent to Bilfinger Noell in Würzburg, where they are integrated to superconducting quadrupole modules.

The integration of the quadrupole modules generates a complex system consisting of parallel hydraulic circuits for liquid and gaseous helium and a vacuum system whose walls have temperatures between four and ten Kelvin. Extreme demands are also made, for example on the positional fidelity of the components when cooling from room temperature to the 4.5 Kelvin operating temperature of the magnets. Although the cold mass is built on a carrier consisting of two separate support structures, their position in the cold state may only deviate from the nominal value by a maximum of 0.1 millimeters. The properties of each integrated module must therefore be examined and confirmed in a separate cold test.

The cold testing of 81 of the 83 SIS100 quadrupole modules was made possible on the basis of a Memorandum of Understanding (MoU) between the German Federal Ministry of Education and Research and the Italian Ministry of Education, Universities and Research. The Salerno site offered ideal conditions for this. A cryogenic test facility for testing FAIR-SIS300 magnets had already been built within the campus of the University of Salerno.

Building on these good prerequisites, the local INFN team led by Dr. Umberto Gambardella has now developed, procured and built all the additional equipment necessary for testing the SIS100 quadrupole modules. In addition to the actual cryogenic system, measurement systems for the electrical circuits of the magnets and systems for monitoring superconductivity (quench detection) also had to be developed and built.

In the course of this year, the THOR cryogenic test facility was cold run and commissioned for the first time. For this purpose, the first SIS100 quadrupole module (FoS, First of Series) was brought to Salerno and assembled at the test facility. The Italian team had previously been trained at GSI to test the modules, and a continuous exchange of information has been set between the GSI and INFN groups.

The Italian scientific community and GSI/FAIR are closely linked in many areas. The Scientific Managing Director of GSI and FAIR, Professor Paolo Giubellino says: Our collaboration with Italy is of great importance. Italian researchers are represented in many fields and collaborations at GSI and FAIR and are making excellent contributions. Italy and INFN in particular have a very strong scientific and technological participation in FAIR, contributing to both the accelerators and the experiments. We hope this involvement will eventually become a full membership. I am delighted about this further deepening at the test facility THOR and the enhancement of our successful cooperation.” (BP)