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

Christopher T. Lyne, Miron F. Liu, Joshua L. Rovey

Research output: Contribution to journalArticlepeer-review

Abstract

The time-of-flight mass spectrometer (ToF-MS) is a useful tool for quantifying the performance of electrospray thrusters and characterizing their plumes. ToF-MS data can be used to calculate the mass-to-charge distribution in the plume, but the kinetic-energy-to-charge (i.e., the potential) distribution must be known first. Here we use a ToF-MS in tandem with a retarding potential (RP) analyzer. By sweeping the retarding potential through the range of potentials present in the plume, both the mass-to-charge distribution and the potential distribution can be measured independently. We demonstrate this technique in a case study using a capillary electrospray emitter and the ionic liquid propellant 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, abbreviated EMI-Im. We report a linear correlation between retarding potential and mass-to-charge ratio that agrees with published data from more complex orthogonal RP/ToF-MS instruments. Calculated values for the jet velocity and jet breakup potential match within 2% and 12%, respectively. Using conventional ToF-MS, we estimated the propellant flow rate and compared those estimates to direct flow rate measurements. For flow rates between 233 pL/s and 565 pL/s, the error in ToF-based flow rate estimates ranged from -16% to -13% when the plume potential was assumed to be a function of mass-to-charge. Assuming a constant plume potential yielded mixed results. However, using the average stopping potential measured by a retarding potential analyzer resulted in higher errors, ranging from -26% to -30%. Data and MATLAB code are included as supplemental materials so that readers can easily apply the techniques described here.

Original languageEnglish (US)
Article number13
JournalJournal of Electric Propulsion
Volume2
Issue number1
Early online dateMar 31 2023
DOIs
StatePublished - Dec 2023

Keywords

  • Electrospray propulsion
  • EMI-Im
  • Plume diagnostics
  • Time-of-flight

ASJC Scopus subject areas

  • Mechanical Engineering
  • Physics and Astronomy (miscellaneous)
  • Aerospace Engineering

Fingerprint

Dive into the research topics of 'A simple retarding-potential time-of-flight mass spectrometer for electrospray propulsion diagnostics'. Together they form a unique fingerprint.

Cite this