Experimental measurement of neoclassical mobility in an annular malmberg-penning trap

An annular Malmberg-Penning trap confining a non-neutral plasma of electrons has been operated with an azimuthal magnetic field to create drifts orthogonal to the magnetic flux surfaces. An applied electric field and collisions with added helium drive transport by electric mobility. The measured confinement times have the expected neoclassical magnetic-field dependence, are approximately 0.8 of the value based upon the neoclassical mobility, and differ from the classical value by more than a factor of 3 at the highest value of azimuthal field.