Method and apparatus for mass spectrometric analysis at ultra-low pressures

A trapped ion cyclotron resonance mass spectrometer comprised of an analyzer cell having upper, lower, side and end electrodes positioned to produce a substantially uniform electric field, a magnet positioned to produce a magnetic field and irradiating wires adjacent to the electrodes for producing an RF alternating field. The upper, lower and side electrodes are in the form of a rectangular hyberbola to produce a homogeneous quadrupolar electrostatic field. Sample ions are produced by reaction with a reagent ion and trapped by the electric and magnetic fields. The magnetic field induces the trapped ions into an orbit at a frequency related to the charge-to-mass ratio. The analyzer cell is then irradiated with an alternating electric field which causes the ions to accelerate until they impinge on the upper and lower electrodes and are collected. An electrometer connected to the upper and lower electrodes senses the collected ions and measures the current produced.