The Lissajous figures of RF discharge under different pressures. (a) 500 Pa, PI = 20 W, PL = 12 W; (b) 1000 Pa, PI = 20 W, PL = 15 W; (c) 5000 Pa, PI = 20 W, PL = 18 W; (d) 20000 Pa, PI = 20 W, PL = 19 W; (e) 40000 Pa, PI = 50 W, PL = 25 W; (f) 60000 Pa, PI = 70 W, PL = 65 W; (g) 70000 Pa, PI = 92 W, PL = 76 W; (h) 96000 Pa, PI = 140 W, PL = 100 W. |