A comb-sampling method for enhanced mass analysis in linear electrostatic ion traps

Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, United Kingdom
Review of Scientific Instruments (Impact Factor: 1.61). 05/2011; 82(4):043103 - 043103-12. DOI: 10.1063/1.3572331
Source: IEEE Xplore


In this paper an algorithm for extracting spectral information from signals containing a series of narrow periodic impulses is presented. Such signals can typically be acquired by pickup detectors from the image-charge of ion bunches oscillating in a linear electrostatic ion trap, where frequency analysis provides a scheme for high-resolution mass spectrometry. To provide an improved technique for such frequency analysis, we introduce the CHIMERA algorithm (Comb-sampling for High-resolution IMpulse-train frequency ExtRAaction). This algorithm utilizes a comb function to generate frequency coefficients, rather than using sinusoids via a Fourier transform, since the comb provides a superior match to the data. This new technique is developed theoretically, applied to synthetic data, and then used to perform high resolution mass spectrometry on real data from an ion trap. If the ions are generated at a localized point in time and space, and the data is simultaneously acquired with multiple pickup rings, the method is shown to be a significant improvement on Fourier analysis. The mass spectra generated typically have an order of magnitude higher resolution compared with that obtained from fundamental Fourier frequencies, and are absent of large contributions from harmonic frequency components.

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    • "With the appropriate potential applied to two focussing lenses, ions were trapped on stable trajectories and over time separated into different ion bunches depending on their mass to charge ratio. Signals from these ion bunches were acquired from the image charge induced on a pickup electrode and mass spectra were obtained using the frequency analysis algorithm CHIMERA which provided a resolving power of up to 10 4 [49]. "
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