The HESR Stochastic Cooling System, Design, Construction and Test Experiments in COSY

The construction phase of the stochastic cooling tanks for the HESR has started. Meanwhile two pickups (PU) and one kicker (KI) are fabricated. One PU and one KI are installed into the COSY ring for testing the new stochastic cooling system with real beam at various momenta. Small test-structures were already successfully operated at the Nuclotron in Dubna for longitudinal filter cooling but not for transverse cooling and as small PU in COSY. During the last COSY beam-time in 2017 additional transverse and ToF cooling were achieved. The first two series high power amplifiers were used for cooling and to test the temperature behavior of the combiner-boards at the KI. The system layout includes all components as planned for the HESR like low noise amplifier, switchable delay-lines and optical notch-filter. The HESR needs fast transmission-lines between PU and KI. Beside air-filled coax-lines, optical hollow fiber-lines are very attractive. First results with such a fiber used for the transverse signal path will be presented.