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Title: Factors affecting the performance of a quadrupole mass spectrometer
Author: Hogan, Thomas James
ISNI:       0000 0004 2736 3493
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2011
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A Quadrupole Mass Filter (QMF) is a key component of a Quadrupole Mass Spectrometer (QMS) that provides the mass to charge discrimination required to separate the component species of a sample. A custom software package has been developed that accurately simulates the performance of the QMF. When used in conjunction with a public domain field solver program a powerful software tool box is created that can accurately predict the performance characteristics of a range of QMF electrode geometries. This software toolbox has been used to investigate the effects of the ratio of circular electrode radius r to electric field radius ro for zone 1 (a = 0.237, q = 0.706) and zone 3 (a= 3.16, q = 3.23) operation. The magnitude and variation of the 'tail' in the mass spectral peak shapes apparent for zone 1 is much decreased for zone 3 and does not influence QMF resolution. In collaboration with the Atomic Weapons Establishment (AWE) the requirements for a QMF and Electronic Control Unit for integration into a QMS were investigated. The QMS is be used for the qualitative and quantitative identification of Hydrogen and Helium isotopes. To successfully separate Hydrogen Tritium (HT) from diatomic Deuterium (D2) a resolution greater than 930 is required. Simulation results demonstrated that this is achievable if hyperbolic profile electrodes are used in conjunction with operation in stability zone 3. A second investigation undertaken as a collaborative project with the Massachusetts Institute of Technology (MIT) investigated the characteristics of a QMF manufactured using Micro-Electro Mechanical Systems (MEMS) technology. The process technology employed is more suited to the manufacture of square electrodes which produce electric fields that are far from optimum. Results show that this limitation in the electric field can be significantly overcome by operating the QMF in zone 3. Some of this data together with information provided by users of QMSs was used to develop a specification for an electronic control unit (BCU) for a QMS. An ECU has now been designed and manufactured. The testing and evaluation of the ECU has now commenced.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral