Method and apparatus for the accumulation of ions in a trap of an ion cyclotron resonance spectrometer, by transferring the kinetic energy of the motion parallel to the magnetic field into directions perpendicular to the magnetic field

摘要

Method and apparatus for introducing ions into an ion trap of an ion cyclotron resonance spectrometer, the ion trap being arranged in a constant homogeneous magnetic field and comprising walls which are designed as electrodes and extend in parallel and/or perpendicularly to a symmetry axis having the direction of the magnetic field and which are supplied with electric trapping potentials retaining the ions in the ion trap, one of the walls which extend perpendicularly to the magnetic field being provided with a hole, the method including the steps of generating the ions outside the ion trap, forming the ions into an ion beam, directing the ion beam upon the hole in the one wall of the ion trap, in the direction of the magnetic field, and reducing thereafter the velocity component, in the direction of the magnetic field, of the ions which have passed the hole and entered the ion trap, below the value determined by the trapping potentials which is needed by the ions for leaving the ion trap, characterized in that the ions that have entered the ion trap are imparted a second motion component in a direction perpendicular to the magnetic field, such that the magnitude of the vector sum of the two ion velocity components remains the same.