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 5566.4 K to 5855.3 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 5203.7 K at 15 Pa to 5941.3 K at 55 Pa, before decreasing slowly to 5855.3 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. © 2016, Science Press. All right reserved.