Characteristics of DC arcs in a multi-arc generator and their application in the spheroidization of SiO2Project supported by the National Natural Science Foundation of China (Grant Nos. 11875295 and 11535003), the National Key R&D Program of China (Grant No. 2019YFC0119000), Provincial Science and Technology Major Project of Anhui Province, China (Grant No. 17030801035), and Key Program of 13th Five-Year Plan, CASHIPS, China (Grant No. KP-2017-25)

We investigate characteristics of multi-arc torches with three pairs of electrodes (three cathodes and three anodes) and their performance on the spheroidization of SiO2 powder. The effect of electrode arrangement, including adjacent pattern (AD pattern, adjacent electrodes powered by one power supply) and opposite pattern (OP pattern, opposite electrodes powered by one power supply), on the dynamics of arc plasma is investigated based on synchronous acquisition of electrical and optical signals. The results show that both the voltage and spatial distribution of each arc of multiple arcs are more stable compared with those of a single arc. The fluctuation of an arc in multiple arcs mainly comes from the small-scale arc-to-arc restrikes among multiple arcs. Moreover, these arc-to-arc restrikes occur more frequently among multiple arc columns in OP pattern than in AD pattern. Moreover, the high-temperature area of the central region of arc chamber in OP pattern is larger than that in AP pattern. For the spheroidization of SiO2 in this multi-arc generator, the spheronization degrees of plasma treated silica in OP pattern are at least 20% higher than those in AD pattern.