The Basic Character of Emission Spectra of He Plasma fromNormal Pressure to Ultra-Low Pressure

The emission spectra of He plasma were measured by using three types of experiment devices: dielectric barrier discharge device, hollow-cathode discharge device and Penning discharge device. From the spectral emission under different conditions, the intensity of spectral line 3~1P_1→2~1S_0 is always the strongest, probably indicating that high density of metastable helium atoms exists. But we also observed different features in three-type devices. Dielectric barrier discharge device can produce semi-plasma, but the spectral lines of He are very weak. Hollow-cathode discharge and penning discharge can discharge in a static steady pressure and the spectral intensity is rather strong. The intensity of spectral lines decreases with the increase of the pressure in penning discharge indicates that the consistence of metastable helium atoms varies under different pressures. Spectral lines have been identified. All results indicate that the spectroscopic analysis of atom emission is an effective way to study the state of He plasma under different conditions.