The theoretically favorable plasma-confinement properties of field-reversed magnetic field configurations have led to many reactor proposals. 1 " 5 Such configurations have been experimentally realized (i) by the injection of relativistic electron beams 6 to form a reversed-field electron ring, 7 (ii) by plasma currents induced by relativistic-electron-beam injection, 8 and (ill) by reversed-field 0 pinches. 9 However, synchrotron-radiation energy losses make a relativistic electron ring unsuitable for a fusion reactor. Indeed, Christofilos amended his original Astron concept 1 by replacing electrons with high-energy protons. Developments in intense-ion-beam 10 " 13 technology make it possible for a reversed-field ion ring to be produced by single-pulse injection. 2 This has led to two experimental programs 12 * 13 aimed at the injection and trapping of an ion ring in a mirror magnetic field.In this Letter, we report experimental results on the production and propagation of a rotating beam of the type required for ion-ring formation.