STOCHASTIC COOLING FOR THE HESR AT FAIR

The High-Energy Storage Ring (HESR) of the future International Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt is planned as an anti-proton cooler ring in the momentum range from 1.5 to 15 GeV/c. An important and challenging feature of the new facility is the combination of phase space cooled beams with internal targets. The required beam parameters and intensities are prepared in two operation modes: the high luminosity mode with beam intensities up to 1011 anti-protons, and the high resolution mode with 1010 anti-protons cooled down to a relative momentum spread of only a few 10-5. Consequently, powerful phase space cooling is needed, taking advantage of high-energy electron cooling and high-bandwidth transverse and longitudinal stochastic cooling. A detailed numerical and analytical approach to the Fokker-Planck equation for longitudinal filter cooling including an internal target has been carried out to demonstrate the stochastic cooling capability. The great benefit of the stochastic cooling system is that it can be adjusted in all phase planes independently to achieve the requested beam spot and the high momentum resolution at the internal target within reasonable cooling down times for both HESR modes even in the presence of intra-beam scattering. Experimental stochastic cooling studies with the internal ANKE target to test the model predictions for longitudinal cooling were carried out at the cooler synchrotron COSY. The routinely operating longitudinal stochastic cooling system applies the optical notch filter method in the frequency band I from 1-1.8 GHz