The upgraded successor to France's record-setting Tore Supra, WEST is a superconducting tokamak at CEA Cadarache equipped with an ITER-like tungsten divertor to test long-pulse, reactor-relevant plasma-wall interactions.
The WEST (W Environment in Steady-state Tokamak) project transformed the former Tore Supra tokamak at the CEA Cadarache research center in southern France into a dedicated test platform for ITER-relevant plasma-facing technologies. The "W" in the name refers to tungsten (chemical symbol W), the refractory metal chosen for ITER's divertor. WEST resumed plasma operations in late 2016 following a multi-year upgrade campaign.1
Tore Supra, which operated from 1988 to 2013, was a pioneering superconducting tokamak that held the world record for the longest sustained plasma discharge—six minutes and thirty seconds in 2003, with an injected energy of 1.07 GJ. Its superconducting toroidal-field coils, made of NbTi cooled by superfluid helium at 1.8 K, enabled truly steady-state magnetic-field operation, a prerequisite for long-pulse plasma experiments.2
The WEST upgrade retained Tore Supra's superconducting magnets and vacuum vessel while installing a full tungsten actively cooled divertor based on the ITER divertor design. This included ITER-grade tungsten monoblock targets bonded to CuCrZr cooling tubes—the same technology that will face the most extreme heat loads in ITER.1
WEST's primary mission is to validate the performance and durability of tungsten plasma-facing components under integrated tokamak conditions: long pulses (minutes to tens of minutes), reactor-relevant heat fluxes (10–20 MW/m²), and real plasma chemistry including hydrogen isotope retention and impurity transport. No other operating tokamak combines superconducting steady-state capability with a full ITER-technology divertor at this scale.3
Beyond materials testing, WEST contributes to the physics of long-pulse plasma control, including real-time wall-condition management, tungsten impurity accumulation in the plasma core, and sustained H-mode operation. These are critical operational challenges that ITER will face during its deuterium-tritium campaigns.
Since restarting operations, WEST has conducted multiple experimental campaigns exploring progressively longer plasma durations and higher heating powers. The machine benefits from a suite of lower hybrid current drive (LHCD) and ion cyclotron resonance heating (ICRH) systems, delivering combined auxiliary heating power exceeding 12 MW. Researchers have studied real-time heat-flux monitoring on divertor targets, fuel retention in tungsten surfaces, and advanced plasma scenarios aimed at minimizing core tungsten contamination.4
WEST operates within the broader EUROfusion research framework and maintains close ties to the ITER Organization, located just a few kilometers away at the same Cadarache site. Its results complement those from JET (prior to decommissioning), ASDEX Upgrade, and other European tokamaks, collectively building the operational knowledge base needed for ITER's success.5