A toroidal plasma is a plasma discharge configured such that the plasma operates in a closed loop. There are no physical electrodes in the discharge chamber, which means that very high electrical currents can be obtained in the discharge, without corresponding problems with electrode erosion. Toroidal discharges have been used for many years in the semiconductor industry, for generation of large fluxes of atomic species such as O, N, H and F, in applications including CVD chamber clean, photoresist removal, and surface oxide removal. 

We have adapted the toroidal plasma technique to growth of high-quality CVD diamond material.  One of the early challenges we needed to overcome was the extremely high-power density on our process chamber inner walls. We employed sophisticated finite element modeling in order to design a process chamber and sample holder able to manage these conditions. Here is an example of thermal modeling that we have done: