The velocities and energies of ions moving in strong electric and arbitrary magnetic crossed fields

The average velocities and energies of ions through a gas in almost perpendicular electric and magnetic fields are calculated. The electric field is taken to be strong enough to give ion energies of a few eV or more, but the magnetic field strength is arbitrary. Symmetric charge exchange is taken to be the most important type of ion collision, and the average initial energy and mean distance moved by the fast neutrals so formed are also briefly discussed. Ion-ion Coulomb collisions and elastic ion-neutral collisions are included as subsidiary types of collision. Symmetric charge exchange produces a large anisotropy in the ion energy which is reduced by the Coulomb and elastic scattering. Expressions are found for the resulting average ion energy parallel to the magnetic field. Examples show that with ion energies of more than a few eV the parallel energy caused by neutral scattering is less than a few percent of the total average energy.