“…T e is obtained from the slope of the IV characteristic curve, and n e can be determined from the ion saturation current (I sat = αn e eA s √ KT e /m i ) with an assumption of T e T i at non-thermal plasma, where α, e, A s and K are coefficients for the collective ion saturation current, electron charge, sheath area and Boltzmann constant, respectively. A s ≈ A p (probe tip area 2 × 10 −4 cm 2 ) is assumed and α ≈ 0.61 is used for un-magnetized plasmas [19,20]. To reduce the signal uncertainty, two cylindrical probes are used, as shown in Figure 3.…”