The author proposes the use of a circular accelerator for gram-size superconducting macroparticles, with the acceleration to the velocities needed for impact fusion performed by a magnetic travelling wave. It is suggested to use the recently discovered high-Tc superconductors both for the macroparticle and for the establishment of the waveguide field. To give the macroparticle a large magnetic moment, it is proposed that it be composed of a densely packed lattice of superconducting grains embedded in a suitable insulator. Since the macroparticle can be kept in a stable orbit by a Braunbeck levitation configuration, the guide field can be static. The macroparticle can then be slowly accelerated along its circular track by a travelling magnetic wave, the field strength of which can be much weaker than the strength of the guide field so that the travelling wave can be generated by ordinary magnetic field coils. In a typical example, the accelerator would have a circumference of about 10 km and, to reach a velocity of about 200 km·s−1 as needed for impact fusion, the projectile would have to make about ten runs with an acceleration length of ∼ 100 km. For a gram-size projectile the kinetic energy would be large enough to ignite a thermonuclear microexplosion.