The GEA XH compressors before delivery. Image credit: GEA

The GEA XH compressors before delivery. Image credit: GEA

GEA Grasso screw compressors for the compression of helium gas are playing a crucial role in one of the world’s largest construction projects for cutting-edge international research.

The compressors are part of the FAIR (Facility for Antiproton and Ion Research) particle accelerator facility for cooling superconducting magnets.

The order placed with GEA by the project partner Enerproject S.A. includes compressors type XH, GEA’s largest compressors, XE compressors and XC compressors, all belonging to GEA’s proven LT series.

The GEA compressors are the driving force of the process to liquefy the helium and thus cool the superconducting magnets.

The entire refrigeration system will have a cooling capacity of 15kW at about -269°C. The ions are accelerated with high electric fields. Magnets are used to direct and bundle them. The ions can be accelerated to a maximum speed of around 90% of the speed of light, i.e. almost 270 000 km/s.

Researchers from all over the world use the accelerated ions at GSI for experiments in a variety of research fields, from particle, nuclear and atomic physics to plasma physics, materials research, biophysics and tumour therapy.

The GEA team in the GSI/FAIR project, together with partners such as Enerproject S.A. and Linde Kryotechnik AG, both from Switzerland, faced major challenges — and mastered them.

To cool the magnets, it is not possible to use ammonia or any other refrigerant to reach the required temperature. This is only possible with helium, the ‘coldest’ element on earth. The normal boiling point of helium is 4.2K, which corresponds to about -269°C. The entire plant contains 12.5 tonnes of helium.

Project manager for gas compressors, Gerald Geißler, said helium is an expensive and extremely rare chemical element that cannot be produced artificially.

“Therefore, the loss and contamination of helium must be minimised in order to reduce costs for the customer. For this reason, the installation of a second O-ring seal for the low-pressure compressors, as well as a leak test (sniff test) with helium were necessary,” he said.

According to current planning, the helium compressor plant is scheduled to be commissioned in 2024 and the first jet in 2025.

With this project, GEA demonstrated its competencies not only in ammonia as a natural refrigerant, but also in the compression of gases such as the noble gas of helium.

The company is confident that it will be able to meet further requests for similar helium plants.

The FAIR particle accelerator facility in Darmstadt is one of the world’s largest construction projects for cutting-edge international research. Among other things, an underground accelerator ring tunnel 1 100 meters long, laboratories and other operational and utility buildings are being built on an area of around 150 000 square meters.

The transfer building is the most complex building in the facility. It is the central hub of the facility beamline. The 1 100m tunnel for the SIS100 particle accelerator will also be up to 17m underground. Adjacent to the accelerator tunnel itself will be a supply tunnel that will house, among other things, lines for electricity and liquid helium, space for power supply equipment and facilities for controlling ion beam quality.