  Magnet stability and reproducibility have become increasingly important as
greater precision and beams with smaller dimension are required for research,
medical and other purpose. The observed causes of mechanical and electrical
instability are introduced and the engineering arrangements needed to minimize
these problems discussed; the resulting performance of a state-of-the-art
synchrotron source (Diamond) is then presented. The need for orbit feedback to
obtain best possible beam stability is briefly introduced, but omitting any
details of the necessary technical equipment, which is outside the scope of the
presentation.
