The refractory metal tungsten is recommended as the leading
candidate for the divertor section of the International Thermonuclear
Experimental Reactor (ITER) because of many favorable
properties such as high melting point, high sputtering threshold,
high thermal conductivity and a low coefficient of thermal expansion
[1e5], and copper has been proposed as the heat sink material
behind the plasma facing materials (PFM) due to its high thermal
conductivity, high electrical conductivity and high ductility [6,7].
However, the large difference in melting point and coefficient of
thermal expansion between these two metals makes it very difficult
to join them together.