Generation of inductively coupled thermal plasma with pulse modulated mode

We have newly designed a thermal plasma system which can be operated with a pulse modulated mode for the control of plasma power in the time domain an d for creating non-equilibrium effects such as fast heating or quenching of the plasma to produce new functional materials at a high rate. The system consists of a solid state power supply with a maximum peak power of 30 kW ( 20 kW continuous!, an induction plasma torch with a 13-turns coil of 55 mm diameter and 85 mm length and a vacuum chamber. The pulse modulated plasma was successfully produced at a plasma power of 11 kW and a pressure from 27 kPa to 101 kPa (from 200 to 760 Torr). The on and off time were each 5 ms, which corresponds to a duty factor of 50%. Measurements were carried out o n the time variation of the spectral lines emitted from the ArI species. Th e dynamic behavior of the plasma temperature in an on-off cycle was estimat ed by the Boltzman plot method as an average value for eight emission lines . The excitation temperature of the ArI atom changed periodically from 5000 K to 14000 K during the cycle at 27 kPa. The magnitude of this temperature change was weakened at higher pressure of 101 kPa, The minimum duty factor to sustain the pulse modulated thermal plasma was found to be 30%, which c orresponds to the pulse off time of 10 to 12 ms.