Series production of SIS100 accelerator cavities, power amplifiers and power supply units completed — All components delivered


The heavy ion accelerator SIS100 with a circumference of 1.1 kilometers is the heart of the future accelerator facility FAIR (Facility for Antiproton and Ion Research), which is currently being built at GSI. In the future, it will accelerate the heaviest ions to their maximum velocity within half a second. All the necessary cavities, power amplifiers and power supply units have now been delivered to GSI/FAIR. This completes the series production of the SIS100 main acceleration systems.

The fast acceleration time of the SIS100 is a major difference compared to other superconducting synchrotrons, in particular the large collider synchrotrons, whose acceleration ramp typically takes several minutes. To enable this, SIS100 is equipped with a large number of high-frequency accelerator units. For the initial commissioning, 14 cavities were planned and ordered for the acceleration of the heavy ions; in the final configuration, 20 cavities will be needed. In addition to the radio-frequency systems for beam acceleration, SIS100 has another nine cavities for compression of the accelerated ion pulses and four other special systems. The latter are used on the one hand to stabilize the beam at high intensities and on the other hand to create radiofrequency barriers that enclose a rectangular beam pulse prior to extraction. With this equipment of high-frequency systems, the straight lines of SIS100 are more like a linear accelerator than a synchrotron.

The design and construction of the accelerating cavities was contracted to RI Research Instruments GmbH. A design phase, in which RI worked closely with specialists from GSI's Ring RF department, was followed by the production and acceptance of the first-of-series system. Based on the results of these activities, manufacturing of the 13 series systems, consisting of cavities and power amplifiers, started last fall. At the same time, the associated power supply units were produced in Switzerland by RI's cooperation partner, Ampegon Power Electronics AG, now part of the Aretè & Cocchi Technology Group.

In the beginning of December, the final components for the SIS100 acceleration system were delivered by RI. As a result, all components of the procurement — 14 cavities and power amplifiers each from RI and 14 power supply units from Ampegon — have now arrived at GSI/FAIR. Together with the "low level RF", the electronic system for control and synchronization, they form the acceleration system of the SIS100 synchrotron, which can generate a total peak acceleration voltage of 280 000 volts at the ceramic gaps of the cavities.

Production and acceptance testing faced unexpected challenges in early 2020 due to the corona pandemic, but thanks to shift work, flexible customization, and, most importantly, close cooperation among the teams at GSI/FAIR, RI, and Ampegon, the activities were successfully completed despite the difficult circumstances. In addition to the completion of the series production of the superconducting dipole modules, another important milestone for the construction of the SIS100 synchrotron has thus been reached. (CP)