2. Experiments
2.1. Experimental system
The experimental system is shown in Fig. 1. It consists of five parts: a feed gas system, a DC power supply, a DC binode
plasma generator, a graphite tube reactor and a gas analyzer. The DC thermal plasma generator consists of a button-shaped cathode and two columnar anodes, and each of them is separated by insulating materials, respectively. As we can see,between cathode and the first anode, there is the inlet I to introduce argon as discharge gas; between the first anode and the second anode, there is the inlet II to introduce nitrogen or feed gases as discharge gas. Below the plasma generator,there is the tube reactor. Between them there is the inlet III to introduce feed gases. The discharge is triggered by a high voltage between the cathode and the first anode, and then pushed to the second anode applied a DC voltage. Therefore, the stable discharge is maintained between the cathode and the second anode even if the electric circuit of the first anode is turned off.