Study of initial stages of antiproton trapping processes

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Antiproton beams of 5.9MeV/u are injected and trapped into a 2m Penning trap of 3.5T,and then electron-cooled down to a few eV.It is found that the lifetime of antiprotons in the trap does not depend very much on the outer vacuum from 10^<-9> Torr to 10^<-8> Torr, which indicates that the trapping cross section of slow antiprotons into atomic orbitals may be different from the so-called Langevin cross section, which is a good sign for experiments with gaseous targets, where powerful differential pumping systems are essential. Then extraction schemes of slow antiprotons from the trap have been studied constructing a track detector to determine the anihilation position of extracted antiprotons. In order to realize a differential pumping which amounts to five orders of difference, a differential pumping stage consisting of two turbo pumps, a sublimaion pump, and an ion pump for ultra high vacuum were prepared. Further, a large scale trajectory simulations including several Einzal lenses under varying magnetic field were performed, which proved that a reasonable transportation is possible with the above configurations. Spot sizes of extracted antiproton beams were observed employing a combination of a quartz disc and a high sensitivity CCD camera, which revealed the diameter of extracted antiprotons are about 3mm.