Sirvi Kuupäev , alustades "2009-10-02T06:43:34Z" järgi

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Study of negative glow and positive column regions of capillary HF discharge
(2009-10-02T06:43:34Z) Raud, Jüri
In the present thesis excitation mechanisms of helium atoms and ionization mechanisms of nitrogen molecules in He / N2 mixtures of y-mode HF capillary discharge were studied. Two discharge regions- negative glow and positive column were under investigation. Experiments were carried out at middle pressures, N2 fraction was varied in 0 - 0.5% range. From electrical parameters i-u characteristics at different N2 concentrations were recorded and phase shift between i and u was determined. On the basis of results of electrical measurements the electron density was calculated and the electric field strength in the positive column was determined. Discharge spectra as a function of discharge current, total pressure and N2 concentration were recorded. On the basis of spectral measurements the concentration of He metastable state atoms and the rotational temperature of N2+(B) state were calculated. Experimental results allowed to clarify the dominating He excitation and N2 ionization mechanisms. In the negative glow region: (i)He is excited dominantly via He2+ recombination in reactions He2+ + e -> He* + He and He2+ + e + He -> He2* + He -> He* + 2He; (ii) N2+ ions are produced mainly via charge transfer reaction, He2+ + N2 -> N2+ + 2He. In the positive column region: (i) He excitation occurs mainly via electron impact with metastable state He atom Hem, Hem + e -> He* + e; (ii) N2 ionization occurs in Penning reaction, Hem + N2 -> N2+ + He.