Design considerations for a cycloidal mass analyzer using a focal plane array detector

Abstract

With the advent of technologies such as ion array detectors and high energy permanent magnet materials, there is renewed interest in the unique focusing properties of the cycloidal mass analyzer and its ability to enable small, high‐resolution, and high‐sensitivity instruments. However, most literature dealing with the design of cycloidal mass analyzers assumes a single channel detector because at the time of those publications, compatible multichannel detectors were not available. This manuscript introduces and discusses considerations and a procedure for designing cycloidal mass analyzers coupled with focal plane ion array detectors. To arrive at a set of relevant design considerations, we first review the unique focusing properties of the cycloidal mass analyzer and then present calculations detailing how the dimensions and position of the focal plane array detector relative to the ion source determine the possible mass ranges and resolutions of a cycloidal mass analyzer. We present derivations and calculations used to determine the volume of homogeneous electric and magnetic fields needed to contain the ion trajectories and explore the relationship between electric and magnetic field homogeneity on resolving power using finite element analysis (FEA) simulations. A set of equations relating the electric field homogeneity to the geometry of the electric sector electrodes was developed by fitting homogeneity values from 78 different FEA models. Finally, a sequence of steps is suggested for designing a cycloidal mass analyzer employing an array detector.

Spectral Reconstruction Improvement in a Cycloidal Coded-Aperture Mass Spectrometer

“…As a result, computational reconstruction of the coded spectral data measured at the array detector is simplified because the coded aperture image projected across the detector plane does not exhibit distortion. Spectral reconstruction can be performed under the assumption of a shift-invariant instrument response function (system response function is constant as a function of the system parameters such as electric field, magnetic field, ion mass to charge ratio, and ion velocity) and only requires a simple deconvolution of the aperture image to reconstruct the mass spectrum. − ,− In contrast, 90-degree and Mattauch-Herzog mass analyzers generate a distorted image of the coded aperture at the detector plane and require a more complex reconstruction process . However, reconstruction of experimental spectral data using a cycloidal mass analyzer with a shift-invariant system response can lead to reconstruction artifacts because nonidealities such as field nonuniformity, misalignment, and shallow depth of focus can result in a system response function that varies as a function of the system parameters .…”