Rapid particle acceleration is possible using a fixed-field alternating-gradient machine — but 'scaling' in its design has been necessary to avoid beam blow-up and loss. The demonstration now of acceleration in such a machine without scaling has positive implications for future particle accelerators. Article p243 COVER IMAGE: ANDREW COLLINS COVER DESIGN: ALLEN BEATTIE
The cover image of the March 2012 issue of Nature Physics should have been credited to Andrew Collins. Corrected in the HTML and PDF versions after print, 12 March 2012.