Germany's plasma-wall laboratory — where the science of keeping fusion plasmas clean was written.
TEXTOR — the Tokamak Experiment for Technology Oriented Research — operated at Forschungszentrum Jülich in North Rhine-Westphalia, Germany, from 1983 to 2013. While many tokamaks chased higher temperatures and longer pulses, TEXTOR carved out a distinctive role: it was the world's foremost laboratory for studying plasma-wall interactions, surface conditioning, and the technological challenges of maintaining a clean, controlled fusion plasma in contact with material surfaces.
TEXTOR was a medium-sized circular-cross-section tokamak with a major radius of 1.75 m and a minor radius of 0.46 m. It operated with a toroidal magnetic field of up to 2.8 T and plasma currents up to 800 kA. Unlike diverted machines such as ASDEX, TEXTOR used a toroidal belt limiter — the ALT-II (Advanced Limiter Test) — that defined the plasma boundary through direct contact. This limiter-based design was deliberate: it gave researchers direct access to the plasma-surface interface and made TEXTOR the ideal machine for studying erosion, deposition, fuel retention, and impurity generation.1
TEXTOR made foundational contributions to understanding how plasma interacts with solid surfaces. The machine systematically tested wall materials including carbon, tungsten, beryllium, silicon, and boron-carbide coatings. Its boronization technique — depositing thin boron films on interior surfaces to reduce oxygen impurities — became standard practice at tokamaks worldwide. TEXTOR also pioneered siliconization and lithium wall conditioning, demonstrating how surface chemistry could dramatically improve plasma performance.2
The machine's post-mortem tile analyses provided some of the most detailed data available on material erosion and tritium co-deposition in carbon-walled tokamaks. These findings were directly relevant to ITER's decision-making process on first-wall materials and contributed to the eventual selection of tungsten and beryllium over carbon for ITER's divertor and main chamber respectively.3
In its later years, TEXTOR installed the Dynamic Ergodic Divertor (DED) — a system of helical perturbation coils at the plasma edge that could create controlled magnetic islands and ergodic field regions. The DED was used to study resonant magnetic perturbations (RMPs) and their effect on edge transport and particle exhaust. This work contributed directly to the development of RMP-based ELM suppression strategies now planned for ITER.4
TEXTOR was shut down in December 2013 after three decades of operation. Its closure reflected a broader strategic shift at Jülich toward materials science through linear plasma devices and contributions to the Wendelstein 7-X stellarator program. But TEXTOR's scientific output — over 2,000 publications spanning plasma-surface interactions, edge physics, and wall conditioning — remains a cornerstone of the fusion technology knowledge base. The lessons learned at TEXTOR are embedded in ITER's material choices, wall-conditioning protocols, and plasma-facing component qualification standards.5