Spectra of dense pure hydrogen plasma in Balmer area

Abstract

We study experimentally the pure dense hydrogen plasma spectra in Balmer area. Dense plasma with electron concentrations up to ≈10 19 cm −3 has been created by pulse discharge in quartz capillary. Diagnostics of the plasma is made on the basis of optical measurements at λ=632.8 nm . The temperature profile is defined from independent measurements of brightness and transparency at different distances from the centre of the capillary. Detailed study is performed for two discharge conditions: at electron density N e =6.5×10 18 cm −3 and temperature T=18000 K and N e ≈1.5×10 19 cm −3 , T=23000 K . The self-consistent scheme to calculate the weakly nonideal plasma spectra based on the microfield model and unperturbed oscillator strengths distribution is also described. For the lower density regime we have obtained a satisfactory agreement of measured spectra with calculated ones. For higher electron density the lowering of experimental spectra was obtained near Balmer series limit in comparison with calculations. Further measurements at higher electron densities (N e >10 19 cm −3) are required to prove the obtained tendency for some “clearing up” of dense hydrogen plasma spectra at Balmer area.