  We report the use of an electrostatic MEMS-based device to produce high
quality electron vortex beams with more than 1000 quanta of orbital angular
momentum (OAM). Diffraction and off-axis electron holography experiments are
used to show that the diameter of the vortex in the diffraction plane increases
linearly with OAM, thereby allowing the angular momentum content of the vortex
to be calibrated. The realization of electron vortex beams with even larger
values of OAM is currently limited by the breakdown voltage of the device.
Potential solutions to overcome this problem are discussed.
