Charged particle motion in spatially varying electric and magnetic fields

The motion of charged particles in spatially varying electric and magnetic fields is studied using computational and analytic techniques. The focus of the work is determination of the circumstances for which an adiabatic invariant, defined as the ratio of the energy associated with the particle gyromotion to the local magnetic field strength, is a constant. When it is constant, this quantity is extremely useful in understanding particle motion in a range of applications. This study uses as an example the motion of positrons in spatially varying electric and magnetic fields typical in recent low-energy scattering experiments. The relationship of these considerations to other physical situations is briefly discussed.