Performance of Heavy Ionic Liquids with Porous Metal Electrospray Emitters

A porous metal electrospray emitter has been tested with four different ionic liquids including those comprised with heavy ions. Time of flight experiments were conducted to characterize the emitted species for each liquid and the amount of emitted current as a function of applied voltage. The results indicate that for each ionic liquid, high quality pure ions were emitted containing no observable charged droplets. Additionally, the emitters produced currents that are much higher than those reported for externally wetted needle emitters, with currents greater than 800 nA for EMI-BF4 and greater than 200 nA for heavy ionic liquids. Propulsive figures of merit including thrust and specific impulse are given and analysis shows that while the heavy ionic liquids produce more thrust per unit current than EMI-BF4, the reduction in emitted current causes actually performance to be lower than that of EMI-BF4. Preliminary time-of-flight data is also given for a mixture of two ionic liquids.