Patent ID: 8115165

Claim:
A method of operating a mass spectrometer comprising an electrostatic trap, said electrostatic trap comprising an entrance end, an exit end, an entrance end ion mirror and an exit end ion mirror, a central field-free region, and a longitudinal axis, said mass spectrometer further comprising a mass analyzer enabled to receive ions from said exit end, the method comprising: admitting ions into said electrostatic trap via said entrance end; trapping ions in said electrostatic trap, said ions oscillating between said entrance end ion mirror and said exit end ion mirror along said longitudinal axis; waiting for said ions to separate into bunches of ions of different m/z values via said oscillating; exciting a given bunch of ions of a given m/z value along said longitudinal axis until at least a portion of said given bunch overcomes a barrier field at said exit end ion mirror, thereby exiting said electrostatic trap, leaving behind remaining ions in said electrostatic trap; and analyzing at least a portion of said given bunch via said mass analyzer.