LARGE-A torch to determine and model plasma physics and behavior for CVD process applications

The so-called LARGE- plasma torch consists of an extended arc (up to 45 cm ) which is operated with a perpendicular gas flow producing a rectangular plasma jet with a cross section of ~45 cmtimes2 cm. This torch enables CVD and PVD applications and chemical activation processes over large area in atmospheric pressure environment. Performance was analyzed by high speed imaging, enthalpy probe, emission spectroscopy and tomography measurements leading to the exposure of characteristic instabilities in the arc which translate into fluctuations of the produced plasma jet. Mitigation of these fluctuations was performed by optimizing nozzle and torch geometry based on the use of commercial CFD codes with limited success. Additional attempts to improve stability were made resulting in an improved version (LARGE IV-150) operating more stable with higher efficiency.