Development and evaluation of a low homogeneity magnet for Fourier transform ion cyclotron resonance mass spectrometry

The characterization and evaluation of a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer based on a low homogeneity superconducting magnet is presented. Typical features of a conventional FT-ICR magnet include low ppm homogeneity specifications and a wide diameter bore in the design of the magnet solenoid. These attributes contribute to high cost at larger magnetic field strengths. In this dissertation the analytical performance of a high field magnet with much lower field homogeneity and smaller bore size is examined.;Matrix-assisted laser desorption ionization (MALDI) is used to generate ions for FT-ICR detection. This source offers the twin advantages of generating large mass ions which are less susceptible to field inhomogeneity, and the creation of a nominal gas load in the ionization process. It is shown that by limiting the spatial distribution of MALDI-generated ions using quadrupolar excitation, excellent performance is achieved in a magnet with part per thousand homogeneity. The selection of a unique trapped-ion cell is examined for alternative trapping capabilities of laser desorbed ions. The open geometry design with a single trapping electrode allows ions of all kinetic energies to enter the cell, and a much smaller trapping volume for conducting the FTMS experiment. Ion loss processes specific to low homogeneity magnets are also investigated. One specific mechanism of ion loss is a consequence of ion excitation into the radial magnetic field component that exists within the trapped-ion cell. The perpendicular axial force associated with the B...