Two-Beam Operation in DESIREE

The current status of DESIREE is described, with special emphasis on the setup for collision experiments with ions in both the two electrostatic rings - negative ions in one ring and positive in the other. By measuring the kinetic energy released in mutual neutralization reactions be-tween the two ions at collision energies close to zero eV in 3D, the population of different reaction channels has been obtained. The different steps necessary to set up the beams to get well controlled experimental properties are described as well as the principles behind our automatic optimization routines, which are extensively used with consistent result.