US Patent 7309861 Mass spectrometer

A mass spectrometer is disclosed comprising a guide wire ion guide 1 having an outer cylindrical electrode 2 and an inner guide wire electrode 3. AC and DC potential differences are maintained between the outer electrode 2 and the inner electrode 3 so that ions are radially confined within the ion guide 1 in an annular potential well. The outer electrode 2 may be segmented and axial potential wells created along the length of the ion guide 1 may be translated along the length of the ion guide 1 by applying additional transient DC potentials to the segments forming the outer electrode 2.