(1) Antiprotons enter the capture trap through an electrode, which serves also as degrader. The electrode on the right is on - 30,000 V (repulsive) potential. (2) The antiprotons below 30 keV kinetic energy are reflected. (3) Before they can leave the trap through the entrance electrode, this electrode is also put on -30,000 V, and the antiprotons are trapped. (4) Initially at several tens of keV energy, the antiproton cloud swings through a cold cloud of trapped electrons in the middle of the trap. Through 'friction' the antiprotons loose their energy to the electrons, which stay cool by emitting synchrotron radiation.