Juelich logoThe Cooler Synchrotron and Storage Ring COSY has a race track design and delivers polarised and unpolarised proton and deuteron beams in the momentum range from 300 MeV/c up to 3.7 GeV/c. Two systems for phase space cooling of the beam are in operation: an electron cooler operating up to 645 MeV/c and a stochastic cooling system working up to the maximum momentum. With the phase space cooling high precision beams with a very low emittance can be prepared.

At internal experiments with the stochastic cooling a momentum resolution of δp/p = 2x10-4 (FWHM) is achieved at a beam intensity of about 5x1010 stored protons at the maximum momentum. The beam cooling and the high beam and target polarisation are essential for the spin-filtering studies in progress for PAX. Via resonance extraction the beam can be extracted to the external target stations. Routinely the extraction with stochastic feeding of the resonance (ultraslow extraction) is used which allows long spills with a nearly constant extraction current. The extraction efficiency is above 80% allowing extraction currents of up to 1010 protons per second. For special applications a fast kicker extraction can be used where the full COSY beam is extracted in one bunch of about 200 ns with up to 109 particles. Detector tests for PANDA and CBM are being performed at the external target stations.

The accelerator is fully computer controlled. All machine parameters can be stored and reloaded allowing a rapid change of momentum setting and beam optics. With this concept also very special operation modes can be performed like measuring during ramping or switching between different momentum settings from spill to spill. The whole machine is designed for high precision beams resulting in a very stable operation.
There is no other accelerator in the world which provides cooled proton beam over the whole energy range of COSY for studies at internal and external targets.

The HadronPhysics3 project is supported by the European Union
under the 7th Framework Capacities Programme in the area of Research Infrastructures (RI).