A Kingdon trap is a type of ion trap.
In the Kingdon trap there is no potential minimum to store the ions; however, they are stored with a finite angular momentum about the central wire and the applied electric field in the device allows for the stability of the ion trajectories.[1] It consists of a thin central wire, an outer cylindrical electrode and isolated end cap electrodes at both ends. A static applied voltage results in a radial logarithmic potential between the electrodes. In 1981, Knight introduced a modified outer electrode that included an axial quadrupole term that confines the ions on the trap axis.[2] The dynamic Kingdon Trap has an additional AC voltage that uses strong defocusing to permanently store charged particles.[3] The dynamic Kingdon Trap does not require the trapped ions to have angular momentum with respect to the filament. An Orbitrap is a modified Kingdon trap has been used for mass spectrometry. Though the idea has been suggested and computer simulations performed[4] neither the Kingdon nor the Knight configurations were reported to produce mass spectra, as the simulations indicated mass resolving power would be problematic.