Variations on the Penning Trap Concept

In this chapter, we briefly have a look at a number of variations on the idea of a Penning trap, i.e. at specific deviations from the combination of a homogeneous magnetostatic field with an aligned quadrupolar electrostatic potential. We discuss only those designs that use magnetic and electric fields, i.e. we are not concerned with Paul traps, Kingdon traps and so forth, which are a huge topic on their own.