A simple, inexpensive, and precise magic angle spinning speed controller.

Certain magic-angle spinning heteronuclear dipolar recoupling experiments using rotor-synchronized pulse trains require very precise control of the sample-spinning rate. An inexpensive spinning speed controller for use in magic-angle solid-state NMR experiments is described which can control the spinning rate to within +/- 0.2 Hz. The apparatus is based on a simple micro-controller and is self-contained. Experimental results are presented that show the importance of good spinning speed control.