This article describes a parallel mass spectrometer design suitable for use as an add-on attachment for focused ion beam instruments. It consists of an acceleration transfer lens, an electric sector deflector, and a variable field strength magnetic sector deflector. The magnetic sector is designed to deflect and focus ions having a wide range of charge-to-mass ratios onto a flat plate detector. The size of an aperture inside the acceleration transfer lens can be used to change the spectrometer mass resolution. The simulation results presented in this article predict that it should be possible to perform secondary ion mass spectroscopy analysis on the nanoscale range with the proposed mass spectrometer attachment. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3497021]