Space Systems Engineering
October 7th 2015
COLLOQUIUM
Jules Heldens
will present his final thesis on
October 12th 2015
The title of his presentation is:
Time-of-Flight Mass Spectrometric Analysis of Ionic Liquid Electrospray Emission - Effects of Liquid
Constituents and Ion Transport on Emission of Binary Ionic Liquid Mixtures
Porous Ionic liquid ions sources (ILIS) are under investigation for their potential to provide highly propellant
efficient, low mass and compact propulsion systems for small satellites such as Cube-Sats. Moreover porous
ILIS, which are based on electrospraying and thus operate in vacuum, have the potential to increase the sensor
signal and thus resolution of mass spectrometry setups. Conventional ion sources used in mass spectrometry
operate at ambient pressure making it necessary to pass the emitted ion beam through several vacuum stage
in which significant part of the ion beam, and thus sensor signal, is lost. This improved resolution can be of
benefit to fields such as biology, medicine, chemistry and physics.
However, electrochemical degradation of the ionic liquids used in ILIS based devices causes detrimental
emission current decreases. Although effective mitigation techniques have been proposed the assessment of
their efficacy is hampered by a lack in suitable metrology that can detect and quantify any present
electrochemical decomposition effects. A possible solution would be the detection of the decomposition
products by means of Time-of-Flight Mass Spectrometry (ToF-MS). For detection and quantization to be
possible the ionic liquid components need to be transported within the ionic liquids and then emitted in the
ILIS. To investigate the transport and emission of the ionic liquid components in a ILIS device binary ionic liquid
mixtures have been prepared to mimic the presence of electrochemical reaction products without risking the
decrease in emission current associated with electrochemical effects. In this way it is possible to study the
effects of concentration, ion transport and emission on the resulting mass spectra. Thereby it becomes possible
to assess the possibility of detection and quantization using ToF-MS
Calculations of the expected production rates of electrochemical decomposition show that it is not feasible to
detect such effects using ToF-MS setups optimized for ILIS diagnostics, as used in this investigation, within a
reasonable time. From the ToF measurements of the ionic liquid mixtures it has been observed that there is a
strong relation between the ionic liquid concentrations and the resulting relative quantities of particles species
in the ion beam. Moreover some indication of the effects of ion association in the ionic liquid mixture have
been observed. No clear relation has however been established between the liquid composition and the
resulting mass spectra which makes quantization impossible at this point. Therefore it is concluded that ToFMS can currently not be effectively applied for the envisioned purpose. However the investigation does provide
new information for the assessment of suitability of the porous ILIS devices used in this work for general mass
spectrometry.
It gives us great pleasure to invite you all to his presentation.
The presentation will take place in the building of the Faculty of Aerospace Engineering, Kluyverweg 1, Delft.
Start:
Location:
October 12th, 14:00hr
Lecture Room A
Prof. Dr. E.K.A. Gill,
Chair of Space Systems Engineering