First components for FAIR proton accelerator

Insight into a so-called coupled CH accelerator: The crossed stems allow the oszillation of the electromagnetic fields (H-Mode fields) which accelerate the protons. Photo: Robert Brodhage

The first components for the FAIR accelerator p-Linac have arrived at the GSI site. An acceleration structure and an amplifier for electrical fields, a so-called klystron, are to be commissioned and tested at GSI in the coming months. The linear accelerator p-Linac encompasses seven such systems and ranks among the first machines to be set up at the planned FAIR accelerator facility. It serves to accelerate protons which are to be used to generate antimatter.


The name p-Linac stands for “Proton Linear Accelerator”. It serves to accelerate hydrogen ions, also called protons, utilizing high-frequency electrical fields to this end. An oscillator creates the high frequency of 325 megahertz, which is then amplified in the new klystron and fed into the acceleration structure. The high-frequency fields then bring the protons up to speed inside the structure.


The klystron was built by the French company Thales in Vélizy near Paris. It is 5.2 meters long, weighs 4.2 tonnes and has an output of as much as three megawatts. The accelerator structure was designed and created by researchers at Frankfurt’s Goethe University. At present it is being coated in a layer of copper in the GSI electroplating shop so as to improve its electrical conductivity. Afterwards both devices, combined with other necessary components such as a special high-voltage power supply unit with 110 000 volts, will go into service on the test bench at GSI. In the coming months the components will be tested and put through their paces before being prepared for installation in the FAIR facility. The tendering procedures for the other six of the total of seven modules which make up the p-Linac are currently ongoing.


The protons which have been pre-accelerated in the p-Linac are initially to be accelerated further by the GSI ring accelerator and then by the planned FAIR accelerator SIS100. Thereafter they collide at high speed with a production target for antimatter. In doing so antiprotons, the antimatter counterparts of protons, are produced in large numbers. The researchers intend to collect these in a collector ring and then use them in experiments. Among other things, with the aid of the antimatter they wish to understand how the particles of matter of which our world is made up attain their mass.

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