Volt Ampere Characteristics of Low Current DC Discharges in Ar, H 2 , CH 4 and SF 6

In this paper we show new results for a wide range of characteristics of low current diffuse (Townsend-dark discharge regime) discharges in Ar, H 2 , CH 4 , SF 6 . The measured observables include: volt-ampere characteristics, ranges of free running oscillations, frequency and damping of induced oscillations and we also determine the negative differential resistance (the negative differential voltage to current ratio). The measurements were performed for pressures between 0.027 and 1 Torr and for distances between electrodes in the range from 1 to 3 cm.