ON THE CURRENT EMITTED BY TAYLOR CONE-JETS OF ELECTROLYTES IN-VACUO -IMPLICATIONS FOR LIQUID-METAL ION SOURCES

Approximate scaling laws for the charge and size of the drops ejected from the apex of Taylor cones run in the cone-jet mode (electrospray) are now available for highly conducting electrolytes (10(-4) S/m<K<1 S /m) electrosprayed at atmospheric pressure. In order to confirm that s uch laws do also apply to Taylor cones in vacuo, the current versus li quid flow rate curves I(Q) characteristic of a given liquid are invest igated both in vacuum and in atmospheric pressure air. although the sp rays of drops differ profoundly in both cases, the two corresponding I (Q) curves are nearly identical for relatively involatile liquids such as tributyl phosphate. A discussion on the possible relation between the behavior of Taylor cones of electrolytes of organic liquids and li quid metal ion sources (K similar to 10(6) S/m) is attempted, yielding insights on the role of space charge. However, the electrical conduct ivity variable which dominates the behavior of liquid cones of electro lytes appears to be irrelevant in liquid metals. (C) 1998 American Ins titute of Physics.