Figure - available from: Journal of Physics D: Applied Physics
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I–V curves at the beginning and end of testing for (a) Emitter current and (b) Extractor current. Data were collected for a graphite beam collector plate, at ΔZ = 50 mm.
Source publication
Luminescence at the face of ionic liquid ion sources and nearby facility surfaces is a commonly reported radiative phenomenon that requires thorough examination. In this study, we present magnified images of a single emitter porous-media ionic liquid electrospray in profile, which provides spatial information on the origin of the luminescence. To d...
Citations
... In a more recent study, Kerber et al examined the luminescence generated near the emitter tip of a porous ionic liquid electrospray thruster using high-resolution optical imaging [26]. The term luminescence is often described as cold-light since it originates from systems without a thermal component, in contrast to incandescent systems. ...
... Kerber et al showed that, for their thruster design, the primary source of luminescence occurred near the surface of the extractor orifice. They concluded the signal was due to high energy collisions between emitted ions and the extractor electrode as well as between emitted ions and propellant accumulated on the extractor orifice [26]. Their results conclusively demonstrated that the majority of luminescence observed near the emitter tip of their electrospray thruster was due to the inherent nature of the electrode design and ion emission process. ...
... The experimental system used to acquire the spectral data presented here was previously described and will only be briefly discussed here [26]. A porous borosilicate glass emitter with an average pore size of 1-1.6 µm was loaded with the ionic liquid propellant 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF 4 ), which had been outgassed by vacuum drying. ...
Luminescence spectroscopy was used to examine the dynamics of propellant dissociation near the emitter tip of a single-emitter porous electrospray thruster loaded with the ionic liquid EMI-BF4. Luminescence spectra from CH, C2, CN, NH, BH, Hα, and Hβ were observed and confirmed by comparison with simulated spectra. Analysis of the CH (A ²Δ, v′ = 0) spectra yielded a rotational temperature 3082 ± 30 K while the C2 (d ³Πg− a ³Πu) Swan system yielded rotational temperatures 6252 ± 92 K and 5914 ± 75 K for Δv = 0 and Δv = +1, respectively. Examination of the integrated spectral signals from acquired CH (A ²Δ), BH (A ¹Π), and Hα spectra showed a strong correlation with measured extractor current in both positive and negative polarity mode. The evidence suggests the formation of these electronically excited species is due to dissociative excitation induced by high-energy collisions between emitted ions and propellant accumulated on the extractor orifice. A weak broadband signal was also observed and is likely due to dissociative excitation of the anion, BF4⁻, leading to the formation of electronically excited BF2. Analysis of the neutral gas within the test chamber with a mass spectrometer confirmed the presence of BF2, providing strong evidence the observed broadband signal is the result of BF2.
