Deceleration of antiprotons from MeV to keV energies

Trapping of antiprotons for high precision measurements at the Low Energy Antiproton Ring (LEAR/CERN) requires the deceleration of the antiproton beam from typically 5.8 MeV energy down to 10 keV for final capture in standard Penning traps. Two methods, the degradation of the beam in thin foils and the deceleration of the beam in an inverse cyclotron are investigated so far. The foil technique was successfully demonstrated with trapping efficiencies up to a few 10-4 and is now routinely used in the high precision measurement of the antiproton-proton mass ratio. The degradation foil method is compared with the deceleration technique using an inverse cyclotron tested also at LEAR. (orig.)