EFFECT OF BACKGROUND GAS ON THE CURRENT EMITTED FROM TAYLOR CONES

The current-flow rate characteristics I(Q) of electrified liquid cone jets of highly conductive liquids (K > 10(-2) S/m) are shown to be insensitive to the nature(air, CO2, SF6) and pressure (130 Torr < p < 1500 Torr) of the surrounding gas in the domain of values in which the cone is stable. Yet the mobility of the droplets produced by the breakup of the emitted jet depends considerably on gas pressure, Furthermore, the width of the spray they form increases with gas pressure. We conclude that the I(Q) curve is unaffected by space charge phenomena, This is consistent with earlier evidence indicating that the jet current is fixed entirely inside the meniscus, A cone jet of given flow rate Q is thus an ideal current generator, practically insensitive to the distribution of free charge in the gas or the surrounding electrodes. The minimum flow rate for stability of the cone, Q(min), is also found to be independent of gas pressure. (C) 1995 Academic Press, Inc.