FTICR analysis of the magnetic trapping mode of the electron beam ion trap

An electron beam ion trap is used to produce and confine highly-charged atomic ions in an energetic electron beam (electron trapping mode). After switching off the electron beam the ions remain trapped due to the external magnetic and electric fields. We have investigated the properties of this magnetic trapping mode by use of Fourier transform ion cyclotron resonance mass spectrometry. We found that the number of highly charged ions and the relative species abundance is nearly the same just before and just after turning off the electron beam. The electron trapping mode thus represents an ideal method for filling the trap in situ without the losses associated with transferring the ions from external sources. About 10(5) ions per highly charged species, such as Kr-84(35+), were shown to exist in the trap in the magnetic trapping mode. A lower limit of 1.5 s was placed on the ion confinement time. This length is sufficient for a multitude of experiments which may be carried out in the future and which are impossible in the presence of an electron beam. The magnetic trapping mode thus represents a new opportunity for studying the physics of highly charged ions in regimes that have been previously inaccessible.