Electrohydrodynamic Ion Source

Abstract

An electrohydrodynamic (EHD) technique is used to generate ions from liquid metals. Liquid metal is fed to the tip of a capillary needle emitter with a voltage difference applied between the emitter and an extractor electrode to produce an intense electric field at the liquid surface. Electrostatic forces overcome surface tension forces to produce ions by field emission. When using liquid cesium, time-of-flight mass analysis showed the ion current to be primarily Cs+ with a small percentage of Cs2+ and Cs3+. Electron currents of over 1 mA have been produced by operating the emitter at 2 kV negative. Besides cesium, alkali ion beams have been generated using NaK/cesium alloy and sodium. Calculations show that liquid metals of low work functions appear more suitable for production of atomic ions while higher work functions metals may produce multiatomic ions and charged droplets in addition to atomic ions.

Monodisperse Electrosprays of Low Electric Conductivity Liquids in the Cone-Jet Mode

“…by the fact that even stable liquid metal sprays can be established under vacuum conditions for the direct production of (d) Effect of the Liquid Electric Conductivity and of metal ions (25,26 Since it has been shown that the most important liquid V 01 cm 01 to 10 07 V 01 cm 01 , with the resulting sprays prophysical property in controlling both the stability of the elecducing droplets in the submicron size range. trospray (4,14) and the size of the droplet (13,15) is the In the present study the effect of the liquid electric conducliquid electric conductivity, our investigation mainly focused tivity was studied by doping heptane with different concenon this parameter among all liquid physical properties.…”

Active spacecraft potential control for Cluster – implementation and first results

“…The basic principle (see, e.g. Mahoney et al, 1969) has undergone a major redesign to qualify the sources for space use (see Fehringer et al, 1997). For this instrument, indium (stable isotopes with 115 amu and 113 amu to 95.7% and 4.3%, respectively) has been chosen as the ion-source charge material due to its low vapour pressure, which prevents the contamination of the source insulators and ambient spacecraft surfaces.…”

Micropropulsion for small spacecraft: a new challenge for field effect electric propulsion and microstructured liquid metal ion sources

“…This development was also based on experiments on the emission of caesium ions from capillary tubes. 8 At the European Space Research and Technology Centre (ESTEC), a field emission or FEEP system based on the liquid metal ion source principle with caesium as the propellant has been developed progressively and evolved from a singlepin emitter through linear arrays of stacked needles to the presently favoured slit emitter module. 3 Homogeneous high current ion emission from a micron-sized slit has been demonstrated successfully, 9,10 allowing the occurrence of a linear series of equally spaced emitting sites with a distance of <10 5 m and a linear current density of >5 ð 10 1 A m 1 .…”