tungsten is the refractory metal of choice for 📝fusion machines' highest-heat surfaces, prized for the highest melting point of any metal — 3,422 degrees Celsius — and its reluctance to trap fuel.
The name comes from the Swedish tung sten, "heavy stone," though Swedish itself calls the element volfram, the root of its chemical symbol W. In fusion engineering tungsten is the material answer to the exhaust problem: 📝divertor targets and, increasingly, entire 📝first wall surfaces are armored in it. Against the alternatives its case is comparative. Carbon, long favored for its tolerance of thermal shock, was abandoned because it soaks up 📝tritium; 📝beryllium is plasma-friendly but toxic, dusty, and easily melted — 📝ITER dropped it for tungsten first-wall armor in 2023. Tungsten erodes slowly, retains little fuel, and shrugs off heat loads that would destroy anything else.
Its liability is what it does when it fails: as one of the heaviest elements, tungsten is a high-Z impurity, and even trace concentrations reaching the core drive powerful 📝impurity radiation that carries energy straight out of the plasma. A tungsten-armored machine must therefore keep its armor's atoms out of the 📝plasma it protects — a constraint that shapes edge and exhaust physics as much as the metallurgy itself.