Optimizing Radiofrequency Field and Induction Coupling in Slotted Cold Crucibles

Using radiofrequency (rf) for heating and levitation of alloy samples is greatly simplified by a passive element, the slotted cold crucible (similar to Faraday shield for rf plasma ion sources), which if properly designed can shape and concentrate the axial (non static) magnetic field profile. The effect is better represented and verified in 3D simulations (very time consuming) as shown here, even if some simplified 1D and 2D models may help understanding. Boundary conditions at large radius are discussed. Moreover, the sensitivity to important parameters (levitated weight vs frequency and power, sizes of crucible, sample conductivity, radius of sample to skin depth ratio) are demonstrated in a schematized 3D geometry, easily parametrized. Finally complete 3D simulation of a realistic design (adequate for clean alloy melting) are also reported.