Italy’s purpose-built superconducting tokamak for testing the advanced divertor solutions that DEMO will need to handle reactor-level exhaust power—the single hardest unsolved engineering problem in magnetic fusion.
In a fusion power plant, roughly 20 percent of the total thermal power must be channelled through the divertor—the narrow exhaust region where the magnetic field lines intersect material surfaces. In DEMO-class devices, this translates to heat fluxes that can exceed 20 MW/m², beyond the steady-state tolerance of any known material. The Divertor Tokamak Test facility, under construction at the ENEA Frascati Research Centre near Rome, is designed specifically to develop and validate the plasma-exhaust solutions that will make power-plant divertors survivable.1
DTT is a superconducting tokamak with a major radius of 2.19 m, a toroidal field of 6 T, and a plasma current of up to 5.5 MA. Auxiliary heating of 45 MW—provided by ion-cyclotron, electron-cyclotron, and neutral-beam systems—will drive power across the separatrix at levels sufficient to reproduce the scrape-off-layer conditions expected in DEMO.2 The device is designed for high flexibility: its poloidal-field coil set can produce conventional single-null, double-null, snowflake, Super-X, and X-point-target divertor configurations, allowing head-to-head comparison of competing exhaust geometries on a single machine.
The initial divertor will use ITER-grade tungsten monoblock targets on copper-chromium-zirconium cooling tubes, but the facility is designed for rapid divertor cassette exchange so that alternative concepts—including liquid-tin and liquid-lithium divertors—can be tested in later campaigns.3 This modularity is central to DTT’s mission: no single divertor solution has yet proven adequate for a power plant, and the field needs a dedicated testbed that can cycle through candidates at a pace faster than ITER’s operational schedule allows.
DTT received Italian government funding of approximately 500 million euros, supplemented by EUROfusion in-kind contributions. Civil construction at the Frascati site advanced through the mid-2020s, with magnet fabrication and vacuum-vessel assembly proceeding in parallel. First plasma is targeted for the late 2020s, with full-power divertor experiments to follow in the early 2030s.4
Together with COMPASS-U, WEST, and the upgraded ASDEX-Upgrade programme, DTT forms the European exhaust-solution network. Its unique combination of reactor-relevant power density, divertor flexibility, and superconducting steady-state capability makes it the closest analogue to DEMO exhaust conditions that will exist before DEMO itself is built.5