Elektronenverluste in einem abklingenden Wasserstoffplasma

The time dependence of the electron density in the afterglow period of an electrodeless discharge in hydrogen was measured by means of 4- and 8-mm microwave interferometry. An exponential decay was observed in the late afterglow permitting the evaluation of a time constant in the density range from $10^{12}-10^{10}$ electrons per cm$^{3}$. The decay time of the plasma was influenced by the discharge conditions. Electron losses could be explained by ambipolar diffusion and attachment to impurities. Two diffusion coefficients were found correlated to the discharge duration. The mobility value $\mu_{0}=10.1±1.0 cm^{2}/V · sec$ calculated from the diffusion coefficient found for short discharge pulses agrees with Saporoschenkos mobility value $\mu_{0}= 10.2 cm^{2}/V$ · sec for the H$^{+}_{3}$-ion. A second mobility value $\mu_{0}= 14.8 ± 1.2 cm^{2}/V$ · sec found for longer discharge pulses might refer to the H$^{+}$-ion