Document Detail

High- and low-frequency noise in Cs and in liquid metal ion sources.
MedLine Citation:
PMID:  19111398     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Fundamental Physics space missions set rigid thrust noise limits for liquid metal ion thrusters used as actuators on drag-free platforms aboard the spacecraft. We have measured current-, voltage- and thrust noise of Cs and In LMIS, foreseen as prime candidates in these missions. In the high-frequency range, quasiperiodic oscillations around approximately 10(5)Hz can be observed for both types of emitters with frequency depending on emission current. In the low-frequency range (1-10(-3)Hz), which is particularly important for drag-free control, different types of noise events are observed, which in some instances show definite signs of deterministic chaos (period doubling, self-similarity). High-frequency current oscillations are generally ascribed to electro-hydrodynamic oscillations of the TAYLOR cone and the jet at its apex, with concomitant emission of charged nanodroplets. Comparison of theory and experiment shows unsatisfactory agreement in predicted vs. measured current oscillation frequencies and large disagreement in droplet emission frequencies. No theory is presently available for describing low-frequency noise events. In terms of a linearized Mair theory it is, however, shown that these noise events can be efficiently described by spontaneous variations in electrical emitter impedance. In spite of this impedance noise, the mission requirements for thrust noise (<0.1microN/Hz(1/2)) can be met by a thrust-stabilized In emitter.
F Rüdenauer; J Mitterauer; A Genovese
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Publication Detail:
Type:  Journal Article     Date:  2008-11-21
Journal Detail:
Title:  Ultramicroscopy     Volume:  109     ISSN:  0304-3991     ISO Abbreviation:  Ultramicroscopy     Publication Date:  2009 Apr 
Date Detail:
Created Date:  2009-03-24     Completed Date:  2009-10-08     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7513702     Medline TA:  Ultramicroscopy     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  436-41     Citation Subset:  -    
ARC Research, Functional Materials, A-2444 Seibersdorf, Austria.
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