First technical FAIR facility receives its centerpiece — “Coldbox” of the cooling system for the superconducting accelerator magnets delivered


A large heavy goods transport set off from Aschaffenburg to Darmstadt on November 30, 2022. Its destination was the international accelerator facility FAIR (Facility for Antiproton and Ion Research), which is currently being built at the GSI Helmholtzzentrum für Schwerionenforschung. Loaded was the so-called “coldbox”, a steel tank with a length of 18 meters, a height of more than 4.5 meters and a weight of 85 tons. The coldbox is the heart of the cryogenics facility, produced and installed by Linde engineering. It is used to cool and liquefy helium for the FAIR accelerator. Following the shell construction and the technical building services, the cryogenics plant is the first technical facility to be brought into the FAIR buildings.

The huge cooling facility will supply liquid helium to two key FAIR building blocks, the FAIR ring accelerator SIS100 and also the Super Fragment Separator (Super-FRS). In the future, ions —charged atoms —will whiz around the curves of the SIS100 ring accelerator at up to 99% the speed of light, then collide with samples of materials to produce nuclear reactions. The Super-FRS is a giant sorting machine for newly produced, exotic atomic nuclei which can tell us about states in stars and other stellar events. With these and other large-scale devices, scientists at FAIR hope to bring the universe into the laboratory.

In order to guide the particles along their paths, strong magnetic fields are required in both cases, which can only be achieved through the phenomenon of superconductivity: Extreme cryogenic temperatures can cause the electrical resistance in some materials to nearly disappear, allowing high electrical currents to flow in the electromagnets. To achieve this, the magnets must be cooled to a temperature of four kelvin (- 269°C). For that purpose, the cryogenic system delivers a maximum flow rate of over 21,000 liters of liquid helium per hour, for a total helium storage of nine tons, with a maximum cooling capacity of 14 kilowatts at four kelvin.

“The delivery of the coldbox to the FAIR construction site is a milestone and a sign of the steady progress being made in the construction of FAIR. The coldbox is the heart of the cryogenic facility, the first high-tech system to be installed in the newly constructed FAIR buildings on the construction site. This will bring us a big step closer to our goal of accelerating particles to almost the speed of light. Linde Engineering is an important partner in this process,” says Jörg Blaurock, Technical Managing Director of FAIR and GSI.

“The FAIR cryogenic plant is one of the largest possible refrigeration plants that can still be built from one unit. For even higher cooling loads, several plants would have to be used in parallel,” explains Dr. Holger Kollmus, who as head of the Cryogenics Department at GSI/FAIR is responsible for the construction of the plant. “A special feature of the plant is the possibility to change the cooling capacity dynamically. Comparable plants, which are mainly used for the production of liquid helium, permanently run at full load. Since the required cooling capacity for the accelerator fluctuates depending on the operating condition, the plant is designed to adjust its pressures and mass flows accordingly to save energy and coolant. Efficient response to changing loads places high demands on the design and construction of the unit.”

As a contract partner, Linde Engineering is responsible for the production and installation of the helium cooling facility on site. Two large buildings are available at FAIR to house the plant components and now the coldbox. Several large pieces of equipment, such as compressors, have already been delivered and integrated into the plant in the past weeks. The coldbox, the largest and central component of the system, was manufactured by Linde Engineering at its Schalchen plant. From there, the unit was driven by transporter to Passau, brought to Aschaffenburg by ship and reloaded onto the final heavy goods transport to GSI/FAIR. Mechanical completion of the entire plant is scheduled for mid-2023.(CP)