同轴空心阴极氦等离子体的电子激发温度研究

利用同轴空心阴极放电装置,产生氦低温等离子体。通过对等离子体的发射光谱进行测量和计算,研究放电功率以及氦气压强对等离子体的电子激发温度的影响。结果表明:氦低温等离子体的发射光谱主要由连续谱和原子谱线构成,放电功率和压强对谱线的强度具有明显影响。压强的变化不仅影响电子从电场中获得的能量,还会影响电子与原子的碰撞频率,从而导致电子激发温度随着氦气压强的增大,出现先上升后下降的变化趋势。

Investigation of Electron Excitation Temperature of Helium Plasma in Coaxial Hollow Cathode Discharge

Low temperature helium plasma was generated using the coaxial hollow cathode configuration. In order to study the impact of the discharge power as well as the pressure of helium on the electron excitation temperature of plasma, calculation was performed based on the emission spectra data of plasma under different discharge conditions acquired by fiber optic spectrometer. The variation of electron excitation temperature was analyzed in relation to different experimental parameters. The results demonstrate that the emission spectra of low temperature helium plasma are comprised of continuum emission and the atomic spectrum of helium. The intensity of spectral lines change dramatically under different discharge conditions, although no visible shift of lines is observed. The electron excitation temperature increases almost linearly with the discharge power, rising from 5 566.4 K to 5 855.3 K, which is mainly owing to the growing acquisition of energy from the electric field. With the growth of helium pressure, the electron excitation temperature increases gradually from 5 203.7 K at 15 Pa to 5 941.3 K at 55 Pa, before decreasing slowly to 5 855.3 K at 75 Pa. This is because that the pressure will not only affect the averaged energy of the electrons gained in the electric field, but also the collision frequency between electrons and He atoms. By selecting proper discharge parameters of the coaxial hollow cathode system, the electron excitation temperature of helium plasma can be controlled.