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Emission Modes in Electrospray Thrusters Operating with High Conductivity Ionic Liquids
Open AccessArticle

Polyatomic Ion-Induced Electron Emission (IIEE) in Electrospray Thrusters

Plasma & Space Propulsion Laboratory, UCLA Mechanical and Aerospace Engineering, 420 Westwood Plaza, Los Angeles, CA 90095, USA
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Author to whom correspondence should be addressed.
Current address: UCLA Department of Mechanical and Aerospace Engineering, 420 Westwood Plaza, Los Angeles, CA 90095, USA.
Aerospace 2020, 7(11), 153; https://doi.org/10.3390/aerospace7110153
Received: 1 September 2020 / Revised: 19 October 2020 / Accepted: 21 October 2020 / Published: 24 October 2020
(This article belongs to the Special Issue Electric Propulsion)
To better characterize the lifetime and performance of electrospray thrusters, electron emission due to electrode impingement by the propellant cation 1-ethyl-3-methylimidazolium (EMI+) has been evaluated with semi-empirical modeling techniques. Results demonstrate that electron emission due to grid impingement by EMI+ cations becomes significant once EMI+ attains a threshold velocity of ∼9×105 cm s1. The mean secondary electron yield, γ¯, exhibits strong linearity with respect to EMI+ velocity for typical electrospray operating regimes, and we present a simple linear fit equation corresponding to thruster potentials greater than 1 kV. The model chosen for our analysis was shown to be the most appropriate for molecular ion bombardments and is a useful tool in estimating IIEE yields in electrospray devices for molecular ion masses less than ∼1000 u and velocities greater than ∼106 cm s1. Droplet-induced electron emission (DIEE) in electrospray thrusters was considered by treating a droplet as a macro-ion, with low charge-to-mass ratio, impacting a solid surface. This approach appears to oversimplify back-spray phenomena, meaning a more complex analysis is required. While semi-empirical models of IIEE, and the decades of solid state theory they are based upon, represent an invaluable advance in understanding secondary electron emission in electrospray devices, further progress would be gained by investigating the complex surfaces the electrodes acquire over their lifetimes and considering other possible emission processes. View Full-Text
Keywords: electrospray; lifetime; overspray; secondary electron emission; facility effects; kinetic emission; polyatomic ion; molecule; droplet electrospray; lifetime; overspray; secondary electron emission; facility effects; kinetic emission; polyatomic ion; molecule; droplet
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MDPI and ACS Style

Magnusson, J.M.; Collins, A.L.; Wirz, R.E. Polyatomic Ion-Induced Electron Emission (IIEE) in Electrospray Thrusters. Aerospace 2020, 7, 153.

AMA Style

Magnusson JM, Collins AL, Wirz RE. Polyatomic Ion-Induced Electron Emission (IIEE) in Electrospray Thrusters. Aerospace. 2020; 7(11):153.

Chicago/Turabian Style

Magnusson, Jared M.; Collins, Adam L.; Wirz, Richard E. 2020. "Polyatomic Ion-Induced Electron Emission (IIEE) in Electrospray Thrusters" Aerospace 7, no. 11: 153.

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Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

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