Characteristics and Temperature Measurement of a Non-Transferred Cascaded DC Plasma Torch

Dependence of the current-voltage characteristics of a non-transferred DC cascadedplasma torch used for nanoparticle synthesis, on the plasma current and the plasma argon gas flowrate are reported in this paper. The potential structure inside the torch and its dependence on theplasma current and gas flow rate are also investigated. The arc voltage is seen to exhibit negativecharacteristic for a current below 150 A and positive characteristic above that current value. Thevoltage drop near the electrodes is found to decrease with the increase in plasma current. 25%of the total voltage is dropped near the cathode at a plasma current of 50 A and a argon plasmagas flow rate of 10 liter per minute (LPM), and it decreases to 12% with the current increasing to300 A, and to 17% with a gas flow rate of 25 LPM. The variation in the torch efficiency with thegas flow rate and plasma current is also reported. The efficiency of the torch is found to be between36% and 48%. In addition, the plasma gas temperature at various positions of the reactor andfor different currents and voltages are measured by calorimetric estimation with a heat balancetechnique.