Europe and Japan reach full accelerator configuration at LIPAc

The Linear IFMIF Prototype Accelerator (LIPAc) is set to break new ground in fusion. After its latest and most delicate upgrade, the machine has reached its full configuration and is ready to enter a new phase of commissioning towards unprecedented performance levels.

Europe and Japan started developing this accelerator in 2007, under the Broader Approach partnership, as a major step in the roadmap towards fusion power plants. The aim of LIPAc, part of the IFMIF-EVEDA project, is to validate the design of an IFMIF type fusion neutron source particle accelerator. By building and operating it, experts are demonstrating how to recreate the intense irradiation conditions inside a fusion reactor. This know-how will then be used in facilities like IFMIF-DONES to test which materials can endure these extreme conditions.

Fusion for Energy (F4E) and QST opted for a staged plan to build this one-of-a-kind machine in Rokkasho (Japan). Starting from the particle injector, the teams built and validated the accelerator one section at a time, with contributions from laboratories and industry. From the European side, at least 50 European companies were involved.

A glimpse into the accelerator vault today reveals a sophisticated 36-meter line of interlinked technologies. Among them stands out a large steel cryostat with magnetic shield and thermal screen, containing the powerful Superconducting Radio Frequency (SRF). This section, provided by Europe and installed during last year, is the key to LIPAc's performance leap. By creating strong electromagnetic fields, it will help speed particles up to 9 MeV of energy, at a current of 125 mA in continuous-wave operation - a highly demanding and never proven regime.

How will we get there? With the assembly completed, the teams will gradually bring the accelerator to life. The commissioning sequence will start by powering the SRF line at room temperature. The system will then be cooled down to 4 K (-269 ºC), a temperature at which its cavities are superconducting, followed by integrated tests with auxiliary and control systems.

After all these thorough checks, the machine will be ready for action. Beam operations are set to begin by March 2027 and last for at least three years. The teams will send first protons and then deuteron particles through the accelerator, progressively ramping up the intensity and duty cycle, from intermittent pulses to a steady beam.

The goal is to reach beam currents far beyond what has so far been demonstrated in continuous wave. At such levels, securing continuous-wave operations is extremely challenging. Hervé Dzitko, IFMIF-EVEDA Project Leader confirms it: "We will likely encounter issues to troubleshoot, but that is in the spirit of the project. LIPAc provides a strategic platform to gain new knowledge, train experts and lift the main technical risks for the IFMIF-DONES accelerator."

Hervé also shares the joint team's excitement for what lies ahead: "We are entering decisive phases. We will turn years of design, procurement, installation and assembly into a proven capability, delivered through the exemplary collaboration between Europe and Japan," he adds.