Penning electrons energy spectra in dc He-Ar microdischarge

Summary form only given. Recently developed new collisional electron spectroscopy (CES) method allows measuring the Penning electron energy spectra in the collisional mode of electron movement at intermediate and high pressures of a main gas^1-3. The nonlocal negative glow plasma of a short (without positive column) dc microdischarge is the most suitable medium. In the nonlocal plasma different groups of electrons do not relax in energy by collisions in the volume and behave independently of each other. The energy spectra of the fast electrons released in Penning ionization of the impurities atoms or molecules by metastable atoms of the main gas represent sharp peaks in the EEDF near the energy of their appearance. The CES method is a new approach for gas impurities detection at high pressures by measuring the energy of the peaks in the EEDF. In our previous papers^2,3 it was demonstrated that maxima in the EEDF appear at the characteristic energies, corresponding to the electrons released in Penning ionization of different atomic and molecular impurities with helium metastable atoms at pressures of the main gas of 7-200 Torr.In this investigation the Penning electron energy spectra in helium - argon microdischarge are presented. The behaviour of the high energy CBS spectrum in wide range of argon admixture concentrations (0.01% - 10%) is studied. The resolution of the CBS method is estimated. The negative glow plasma of a short (without positive column) dc microdischarge is used. Records of the CBS spectra are performed by means of an additional electrode - sensor having large collecting surface and located, in contrast to the classical Langmuir probe, at the boundary of the discharge volume.