Vacuum ultraviolet absorption spectroscopy in the spectral interval of Lyman-α of atomic hydrogen and deuterium in an ion source plasma

Atomic hydrogen and deuterium in the plasma of a magnetic multipole source are investigated with respect to the fraction of the atomic component and the energy distribution of the atoms. Information is obtained by analysis of the wings of the optically thick Lyman-α transitions, and by admixture of small amounts of the other isotope as a thermometer gas in order to warrant transparency in the center of the line. The atom to molecule density ratio is found to be around 15%; the analysis of the energy distributions yields a dominant cold component (Tcold∼400 K), a hot component (Thot≳2000 K) which comprises about 20% of the atoms, and a small but significant amount of fast atoms, described by Tfast with energies up to several eV; the relative amount of these atoms is below 1%.