European systems ready to power Japanese gyrotrons in JT-60SA

JT-60SA, currently the world’s largest Tokamak, is gearing up for the next wave of operations. Built by Europe and Japan as part of the Broader Approach collaboration, the fusion device was operated for the first time in late 2023 and subsequently reached a record-breaking plasma volume of 160 m³. But its scientific journey did not end there. On the contrary, it only just began. The teams in Naka (Japan) are upgrading the machine with more cutting-edge components, procured by Fusion for Energy (F4E) and Japanese institute QST, to achieve hotter, more powerful plasmas in the next phase, planned from 2026.

Among other technologies, the performance leap will rely on new Japanese gyrotrons and European power supplies, working in perfect unison to warm up the plasma. The gyrotrons in JT-60SA work like radio frequency guns shooting high-power microwaves at the plasma. Thanks to a triode design, they will be capable of accelerating electron beams to 1MW at three different frequencies, depending on the heating needs. Their operation is controlled in real time thanks to the precise voltages provided by bespoke power supplies.

F4E partnered with the Spanish company JEMA Energy in 2016 to produce the new set of power supplies. The road to delivery came with its share of challenges, the teams explain. “The design phase was very demanding, given the unique performance requirements. The equipment must deliver extremely stable high voltage and be able to ramp up or shut down within microseconds,” describes Giampaolo Frello, Technical Officer for F4E. Besides, the Covid pandemic put significant constraints on a project spanning two continents.

Despite the complexity, the teamwork between JEMA Energy, F4E and QST prevailed: the first set was manufactured and shipped to Japan. There, trials with dummy loads showed promising results, but the most critical tests came after. Earlier this year, the power supplies and gyrotrons were connected for the first time. With experts from all three teams present, the system performed smoothly, with live voltage changes and an output of 1 MW of radio frequency power.

The teams onsite celebrated the achievement as the fruit of the joint dedication and know-how from Europe and Japan. “The successful integration of our power supplies with the gyrotrons demonstrates their reliability under very strict conditions. Thanks to the close collaboration, the engineering effort paid off, showing that our technology can perform well in a nuclear fusion environment and play a vital role in heating the plasma in JT-60SA,” celebrates Bas Eikelboom, Sales Manager at JEMA Energy.

“This step cements our mutual trust and gives confidence for the production of additional units,” concludes Giampaolo Frello. In fact, F4E and JEMA Energy will keep collaborating to provide more power supply sets, as the experiment team plans to scale up radio frequency heating in later stages (up to 12 gyrotrons and 6 power supply sets).

Europe and Japan built JT-60SA to harvest key knowledge that will feed into ITER and future fusion reactors. Thanks to these technologies, both parties are pushing further the capacity to control burning plasmas, the super-hot state where fusion takes place.