MIRA (Multi-substituted Isotopologue Ratio Analyser) is a mass spectrometer developed to measure the range in composition of isotopologues in CO2. The instrument was conceived, designed, and built by Paul Dennis. The components were engineered by Vacuum Fabrications Ltd., North Walsham Norfolk. Financial support for the instrument is provided by the UEA and the SerCon group Ltd.


MIRA is a symmetric 25cm radius, 120 degree extended geometry mass spectrometer with a 50cm dispersion. It has a Nier type electron impact gas source operating at 8keV, and 6 Faraday cup collectors alligned for detection of m/z = 44 (12C16O16O), 45 (13C16O16O), 46 (12C18O16O), 47 (13C18O16O), 48 (13C18O17O) and 49 (13C18O18O). It's operating mass resolution is 250. The gas dual-inlet system is taken from a 20 year old VG SIRA series II analyser. System control and data acquisition is via National Instruments LabVIEW and cRIO hardware.

The design principles, hardware and performance of the instrument are given in the following pages. Where possible I have included links to schematics, engineering drawings, circuit diagrams, test data and results from the various studies that I am using the instrument for.

MIRA Faraday amplifiers