U+U Collisions near the Coulomb Barrier by Crossing Two Co-Circulating Beams

Experiments with colliding heavy ion beams seem to come into the range of feasibility by means of beam cooling techniques. This note considers, in particular, an alternative to the use of two intersecting storage rings: crossing of two high energy beams co-circulating in one single ring, e.g. in the Experimental Storage Ring ESR [1], on separate closed orbits due to their different magnetic rigidity. Low energy collisions near the Coulomb barrier between two heavy nuclei both highly or even fully ionized or, more generally, systems not accessible to fixed target experiments could be investigated. The study of positron production in the extreme electric field of two colliding, fully stripped uranium ions would be one of the most attractive aims. Estimates for the attainable collision energy, energy resolution and luminosity are given together with a tentative outlook to the experimental arrangement.