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Neutral Beam Test Facility

Third operation campaign beginning on SPIDER

27 Apr 2026

The world’s most powerful negative ion source is entering a new operational campaign at the ITER Neutral Beam Test Facility in Italy, where it is expected to demonstrate stable, high-performance operation at ITER parameters.

The SPIDER negative ion source is heading back into the vacuum vessel of the SPIDER testbed. A new experimental phase is about to start at the ITER Neutral Beam Test Facility in Italy. Courtesy of Consorzio RFX

Following a major upgrade and maintenance campaign at the ITER Neutral Beam Test Facility* in Padua, the ITER-scale negative ion source SPIDER has been re-installed inside of the testbed in preparation for a new experimental phase, SO-3. 

In operation since 2018, SPIDER successfully completed its first campaign in 2021. During a second phase of experiments from 2024 to mid-2025, the ion source reached a record extracted current density of approximately 240 A/m², representing approximately 70% of the target density required for hydrogen neutral beam injection operations at ITER and marking a notable progression in beam performance. The campaign also identified clear ceilings imposed by the existing hardware and allowed engineers to identify a series of necessary design refinements. 

The work carried out during the latest shutdown focused on improving the machine’s reliability and performance. Scientists and engineers completed a broad program of repairs, upgrades and system improvements designed to make SPIDER more robust and flexible and to prepare it for more demanding conditions ahead. The work is expected to improve day-to-day performance while also supporting the long, stable runs needed for ITER’s future neutral beam system.

By resolving issues identified in earlier operational phases and strengthening the platform ahead of more demanding experiments, the upgrades have prepared SPIDER to move closer to demonstrating the capabilities required for ITER-scale negative ion source operation. Courtesy of Consorzio RFX

“The latest upgrade of SPIDER represents an important step toward the objectives defined as part of the ITER Research Plan. As we approach the start of the third experimental campaign, this progress reinforces the Neutral Beam Test Facility’s central role in de-risking the neutral beam injectors for ITER,” says ITER’s Pierluigi Veltri, head of the Neutral Beam Project. “With the forthcoming integration of the radiofrequency solid-state power supplies, we are well positioned to deliver key results aligned with ITER’s neutral beam performance requirements.”

The new campaign will focus on demonstrating performance under conditions relevant to ITER and moving closer to proving the capabilities required for full-scale fusion applications.

*The Neutral Beam Test Facility is hosted by the Italian research laboratory Consorzio RFX and funded by the ITER Organization, the European Domestic Agency and the Italian government. The European, Japanese and Indian Domestic Agencies have all contributed with in-kind components; the European Consortium for the Development of Fusion Energy (EUROfusion) is also participating under the terms of a Cooperation Agreement signed in 2020. 

See the full report on the Consorzio RFX website in English or Italian.         

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