Patent ID: 8735812

Claim:
A Kingdon ion trap comprising: a housing electrode; and at least n inner electrodes, which are formed and arranged so that when a potential difference is applied between the housing and the inner electrodes, a radial electric potential distribution Ψ rad is created, which is determined by equations for Cassini curves of the order n greater than, or equal to, three, and an overall electric potential distribution Ψ in polar coordinates (r, φ, z) corresponds to the form Ψ( r,φ,z )=Ψ 1 z 2 /l 1 2 −Ψ 1 r 2 ((1 −k )sin 2 φ+k cos 2 φ)/l 1 2 +Ψ 2 ln {( r 2n −2 b n r n cos( n φ)+ b 2n )/ l 2 2n }Ψ 3 with b≠0 and n≧3, n being an integer, where Ψ 1 , Ψ 2 , Ψ 3 , l 1 , l 2 , k, n and b are all constants which are freely selectable within respective limitations.