• R. Stassen, F.J. Etzkorn, R. Maier, D. Prasuhn, H. Stockhorst
  FZJ, Jülich
• L. Thorndahl
  CERN, Geneva

The COoler SYnchrotron COSY at the Forschungszentrum Jülich is operating now since 1992. Up to 5*10¹⁰ protons can be delivered over a momentum range of 600 MeV/c to 3.6 GeV/c. The prototype of the HESR barrier bucket cavity was installed into COSY and many measurements have been performed. Especially the co-operation of barrier bucket with stochastic cooling has been studied. During the measurements the internal WASA Pellet target was available which is similar to the PANDA target at the HESR. A 1.2m long cryo-tank has been designed and installed to measure the sensitivities of new pickup structures for the HESR stochastic cooling system. Tank design and structures arrangement correspond to the projected HESR stochastic cooling layout. The recent results will be presented.

• H. Stockhorst, R. Maier, D. Prasuhn, R. Stassen
  FZJ, Jülich
• T. Katayama
  CNS, Saitama
• L. Thorndahl
  CERN, Geneva

The High Energy Storage Ring (HESR) of the future International Facility for Antiproton and Ion Research (FAIR) at the GSI in Darmstadt will be built 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. In addition to electron cooling transverse and longitudinal stochastic cooling are envisaged to accomplish these goals. A detailed numerical analysis of the Fokker-Planck equation for longitudinal filter and time-of-flight cooling including an internal target and intrabeam scattering has been carried out to demonstrate the stochastic cooling capability. Model predictions have been compared to experimental cooling results with internal targets at the COSY facility. Experimental results at COSY to compensate the large mean energy loss induced by an internal Pellet target similar to that being used by the PANDA experiment at the HESR with a barrier bucket cavity (BB) will be presented. Experimental tests of stochastic filter cooling with internal target and BB operation as well as expected cooling properties for the HESR are discussed.

• S.A. Martin, R. Gebel, A. Lehrach, B. Lorentz, M. Nekipelov, D. Prasuhn, F. Rathmann, H.-J. Stein, H. Stockhorst, D.M. Welsch
  FZJ, Jülich
• A. Garishvili, A.N. Nass, E. Steffens
  University of Erlangen-Nürnberg, Physikalisches Institut II, Erlangen
• P. Lenisa, M. Statera
  INFN-Ferrara, Ferrara

The PAX Collaboration is planning experiments using polarized Antiprotons. The only experimentally proven method so far which could lead to the production of polarized antiprotons is the spin-filtering. In particular, spin-filtering has been used to generate polarized protons in an experiment at the Heidelberg TSR*. In order to optimize spin-filtering for the production of polarized antiprotons dedicated experiments are planned at COSY with protons and AD (CERN) with antiprotons. The experimentation at COSY has already started in 2007. A decisive experiment has been performed to settle a long controversy about the role of electrons in the polarization buildup by spin-filtering. Instead of studying the polarization buildup in an initially unpolarized beam, the inverse situation was investigated by observation of depolarization of an initially polarized beam. For the first time the electrons of the electron cooler have been used as a target to study their depolarizing effects on the stored beam. At the same time a series of machine experiments have been performed to study the beam lifetime at different energies.

*F. Rathmann et al., Phys. Rev. Lett. 71, 1993, p.1379