[en] The characteristics of stored ions in a Kingdon trap have been investigated. The charge distributions of the stored ions was measured by a time of flight (TOF) mass spectrometer. Storage of Ar^q+ (q 1, 2, 3, 4) produced by electron beam irradiation has been confirmed. The dependence of Ar ion yields on the trapping potential and storage time have been symmetrically studied. Applying a voltage to the end plates is very important for the storage of ions. Remarkable oscillations of the ion yields are found in the decay curves as a function of storage time for Ar⁺, Ar²⁺ and Ar³⁺ indicating periodical motion of each ion group about the central wire. The three dimensional orbits of ions in the trap are analysed by a computer calculation in order to understand the experimental results. (Author)