Patent ID: 7211794

Claim:
An ion cyclotron (ICR) mass spectrometer, comprising: an external ion source arrangement to generate ions to be analysed; an ion storage device arranged to receive and trap the generated ions; ion optics arranged between the ion source and the ion storage device to guide the ions as they pass from the source into the storage device; a measurement cell having cell walls within which is defined a cell volume for receiving ions from the ion storage device, the measurement cell being arranged to be maintained at a pressure lower than that of the ion storage device; ion guide means arranged between the ion storage device and the measurement cell to guide and focus the ions from the ion storage device into the measurement cell for mass spectrometric analysis therein; and a magnet assembly, including a superconducting magnet which has a room temperature magnet bore arranged to receive the measurement cell, the magnet bore having a longitudinal axis; wherein the measurement cell extends in the direction of the longitudinal axis of the magnet bore and is generally coaxial therewith, and wherein the superconducting magnet is arranged to generate a magnetic field with field lines that extend in a direction generally parallel with the said longitudinal axis of the magnet bore, and wherein the ratio, R, of the sectional area of the magnet bore to the sectional area of the cell volume, each defined in a plane perpendicular to the said longitudinal axis, is less than 4.25.