The Myrrha project at Belgium's Nuclear Research Centre (SCK-CEN) has achieved an important milestone after researchers succeeded in accelerating a proton beam through the recently connected radio frequency quadrupole (RFQ), SCK-CEN said. The RFQ is a component of the particle accelerator that will drive the sub-critical research reactor.

Myrrha (Multipurpose Hybrid Research Reactor for High-tech Applications), a sub-critical assembly, will be a 57MWt accelerator-driven system in which a proton accelerator will deliver a 600MeV proton beam to a liquid lead-bismuth (Pb-Bi) spallation target that is in turn coupled to a Pb-Bi cooled subcritical fast nuclear core. “This is an important achievement in the implementation of the Myrrha project,” said Hamid Aït Abderrahim, Myrrha director and deputy director-general of SCK-CEN.

Myrrha will enable research on innovative options for the treatment of high-level nuclear waste and will be crucial for research and production of innovative radioisotopes for cancer diagnosis and less invasive treatment, SCK-CEN said.

“Despite difficult COVID-19 working conditions, the Myrrha accelerator team..connected the RFQ component with the already existing low-energy beam transmission line (LEBT). The next step consisted of fine tuning the RFQ in order to accurately match it to the LEBT. Another major preparatory step consisted of upgrading the ion source amplifier. In addition, an RF power amplifier for the RFQ was developed and constructed.”

In 2019, the first proton beam was generated in the ion source and sent through the LEBT. The accelerator team has now succeeded in sending the first proton beam ever from the ion source via the LEBT through the RFQ with an acceleration of up to 1.5MeV. Early, results confirm the team’s confidence that the accelerator’s high reliability requirements will be met. The initial tests were performed with short (200µs at 0.5Hz) pulses at nominal (115kW) RF peak power and 4mA peak beam current.

Dirk Vandeplassche, who leads the linear accelerator team, said: “The RFQ’s geometry and built quality have proven themselves with this initial test. Our next step is now to obtain detailed proton beam measurements to further optimise the setup."

"Next, we will complete the installation by adding CH accelerating cavities to the system. That will enable us to increase the beam’s energy to 2MeV and eventually to 5.9MeV. The beam will then undergo further optimisation to bring its reliability to the required level. Upon achieving that level, the linear accelerator will be transferred from our UCLouvain partner site to the Myrrha site in Mol.”

The Myrrha project is part of the European Strategy Forum on Research Infrastructures, and is one of three new research reactors in the European Research Area of Experimental Reactors. The others are the Jules Horowitz Reactor at Cadarache in France and the Pallas reactor at Petten in the Netherlands. Construction of the Myrrha reactor is expected to begin in 2026, with full-operation from 2034.

Photo: How Myrrha might look (Photo credit: SCK.CEN)