基于射频放电一维模型的等离子体诊断

Diagnostics of Plasma Based on One-dimensional Model of Capacitively Coupled Radio-frequency Discharge

为深入研究磁流体效应机理,采用阻抗测量的方法,通过对放电波形的处理,得到放电电压幅值、电流幅值及相位角,依据射频放电一维模型建立等效放电电路,对等离子体参数进行诊断。研究表明,采用半峰值法能够精确读取电压电流幅值及相位角;同轴电缆的容性作用对射频放电电路结构有很大影响;在压力P=1 500 Pa,放电频率f=6.2 MHz的静止条件下,电容耦合射频放电等离子体的电导率约为4×10-3 S/m,电子数密度在1016 m-3量级,电导率随着负载功率增大而增大,随磁感应强度变化呈"V"形变化,在磁感应强度较小时,电导率随磁感应强度增加减小,磁感应强度较大时,随磁感应强度增大而增大;电子数密度随着负载功率和磁感应强度增加而增大。

In order to analyze the mechanism ofmagnetohydrodynamic （MHD）, the parameters of plasma in capacitively coupled radio-frequency （CCRF） discharge were diagnosed, and an equivalent circuit was established on the basis of one-dimensional model of CCRF discharge. The phase angle and amplitudes of voltage and current were gained by means of impedance measurement and the discharge waveform analysis. The experiments were performed in the static condition of pressure P=l 500 Pa, discharge frequency f=6.2 MHz. The conductivity of CCRF plasma is about 4×10 3 S/m. The electron number density is on the order of 1016m3. Main conclusions can be drawn as follows： the phase angle and the amplitude of voltage and current can be obtained accurately with the optimization of half-peak method in the discharge waveform analysis; the structure of discharge system will be greatly influenced by the capacitive effect of coaxial-cable; the electron number density of plasma will increase with the rise of load power and magnetic induction intensity while the conductivity of plasma is affected by two significant factors such as the load power and magnetic fietd. The conductivity is positively correlated with the former one while it will change as a ＂V-type＂ with the decrease of magnetic-conductivity. The reduction will generate with the slight decrease of magnetic-conductivity and the induction will appear with the larger decrease.