  Electron vortex beams have been predicted to enable atomic scale magnetic
information measurement, via transfer of orbital angular momentum. Research so
far has focussed on developing production techniques and applications of these
beams. However, methods to measure the outgoing orbital angular momentum
distribution are also a crucial requirement towards this goal. Here, we use a
method to obtain the orbital angular momentum decomposition of an electron
beam, using a multi-pinhole interferometer. We demonstrate both its ability to
accurately measure orbital angular momentum distribution, and its experimental
limitations when used in a transmission electron microscope.
