Linear electric field mass analysis: A technique for three-dimensional high mass resolution space plasma composition measurements

David J. McComas, Jane E. Nordholt, Samuel J. Bame, Bruce L. Barraclough, John T. Gosling

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

A revolutionary type of three-dimensional space plasma composition analyzer has been developed that combines very high-resolution mass composition measurements on a fraction of the incident ions simultaneously with lower mass resolution but high sensitivity measurements of the remaining population in a single compact and robust sensor design. Whereas the lower mass resolution measurements are achieved using conventional energy /charge (E/q) and linear time-of-flight analysis, the high mass resolution measurements are made by timing reflected E/q analyzed ions in a linear electric field (LEF). In a LEF the restoring (reflecting) force that an ion experiences in the direction parallel to the field is proportional to the depth it travels into the LEF region, and its equation of motion in that direction is that of a simple harmonic oscillator. Consequently, an ion's travel time is independent of its initial angle and energy and is simply proportional to the square root of the ion's mass/charge (m/q). The measured m/q resolution, (m/q)/Δ(m/q), for a small LEF-based prototype that we have developed and tested is ≈ 20. In addition, our laboratory measurements with the prototype instrument show that characteristic time-of-flight spectra allow the resolution of atomic and molecular species with nearly identical m/q values. The measured response of the prototype is in excellent agreement with computer simulations of the device. Advanced design work using this computer simulation indicates that three-dimensional plasma composition analyzers with m/q resolutions of at least 50 are readily achievable.

Original languageEnglish (US)
Pages (from-to)5925-5929
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume87
Issue number15
DOIs
StatePublished - 1990
Externally publishedYes

All Science Journal Classification (ASJC) codes

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