Mass flux and current density distributions of electrospray plumes

Abstract

Performance and lifetime analysis of electrospray thrusters requires accurate knowledge of the mass and charge distributions of the plume. Mass flux and current density distributions were measured for a single capillary electrospray emitter using EMI-Im and found to be substantially different across a wide range of flow rates and emission voltages. Mass flux measurements yield an n∼3 super-Gaussian profile across all flow rates and voltages, while current density measurements change shape from n∼1.5–2.5 super-Gaussian profiles monotonically with decreasing flow rate, where n=1 is Gaussian and higher n values correspond to increasingly more flat-top “super-Gaussian” profiles with steeper drop-off toward higher angles. For increasing flow rate, the mass flux profile grows while maintaining its shape, whereas the current density profile exhibits higher kurtosis, i.e., plumes that distribute proportionately more charge to higher angles. Additionally, higher extraction voltages exhibited tilted emission that led to highly off-axis plumes, ∼10°, for both mass flux and current density. Lifetime and performance assessments of electrospray thrusters must consider that mass flux and current density in the plume display different distribution shapes and trends in shape across changes in extraction voltage and flow rate.

A simple retarding-potential time-of-flight mass spectrometer for electrospray propulsion diagnostics

“…8 . The current data (markers) were fit with a super-gaussian distribution (lines) (as described in [ 21 ]), which is an excellent fit for the data at the lowest flow rate, where the center of the current distribution is at the geometric center of the plume. As the beam current increases, the current distribution becomes wider, and the plume begins to tilt off axis ( ).…”

Multiplexed Electrospray Emission of Green Energetic Ionic Liquids from Wedge-Shaped Porous Emitters

“…In such a case, the electrostatic interaction between charged species can affect the beam divergence angle as well as the beam interception by the extractor grid . Moreover, the skewed cone jet occurring in the strong electric field is another crucial factor to reduce the beam extraction efficiency . In contrast, the extraction efficiency of ionized species of EP-36 is slightly lower than that of [EMIM-EtSO 4 ], regardless of the polarity mode.…”

Scalable Microfabrication of Multi-Emitter Arrays in Silicon for a Compact Microfluidic Electrospray Propulsion System

“…These droplets do not scatter enough light to enable the use of optical diagnostics, , and vacuum techniques such as retarding potential and time-of-flight are used instead. In particular, the electrosprays of EMI-Im have been thoroughly studied in vacuum to determine the particle composition and the distribution of charge-to-mass ratios, , as well as the structure of the beams. − …”