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11 MV/m : check!

21 February '24

Major milestone for superconducting cavity of the MYRRHA accelerator!

The superconducting single-spoke cavities are the key components of the MINERVA high power proton linear accelerator. Operating at -271.15°C (just 2 Celsius above absolute zero temperature), 60 of them will boost the beam energy from 16.6 MeV (the output energy of the normal conducting injector) to 100 MeV.

MYRRHA stage-1 pre-series cavities
Two MYRRHA stage-1 pre-series cavities mounted on the insert of the cryostat awaiting RF tests (courtesy CNRS/IN2P3/IJCLab)

The production of all 6 pre-series cavities has been completed by our manufacturing partner RI Research Instruments GmbH (Germany) by the end of 2023. The cavities have since been thoroughly examined at SCK CEN’s collaboration partner CNRS/IN2P3/IJCLab (France), who is also responsible for the cavity design. Dr. Frank Marhauser, technical lead for the RF cavity project at the Belgian Nuclear Research Centre SCK CEN, comments that “the pre-series fabrication and test campaign are utilized to optimize important fabrication and cleaning processes before we head for full series fabrication.“

A major milestone has now been achieved as the first cavity reached a maximum RF field gradient of 11 MV/m without noticeable field emission. This is comfortably above the required operational field and is proof that the design and manufacturing has been successfully optimized together with our scientific and industrial partners over the past few years.

“The delicate superconducting surfaces must be free of particulates as best as practically achievable to meet performance goals,” adds Dr. Marhauser, “and this includes particulates down to the size of micrometers. This can only be realized by immaculate surface cleaning and proper clean room assembly strategies. We have just obtained a crucial experimental verification that this is working. Now it is all about consistency and repeatability.”

“These are remarkable results, encouraging to proceed further with the strategy proposed by the MYRRHA accelerator team under the leadership of Dr. Adrian Fabich, namely conducting this pre-series test campaign in parallel with preparing the upcoming series cavity testing planned to start this summer at another European site. This is highly appreciated and supported” says Hamid Aït Abderrahim, MYRRHA Director General.

What is a single-spoke cavity?

“A cavity is a hollow resonator through which particles pass. Here, RF energy is converted into an electric field that accelerates the particles. A superconducting cavity is cooled to the point where there is  almost no more electrical resistance. By doing so, the applied current, and consequently the electric field generated, can be much larger, in this case up to 11 MV/m.”


Did you know that... the magnets steer and focus the particle beam while the cavities accelerate the particles?

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