R.F. Beam Recombination ("Funnelling") at the CERN PSB by Means of an 8 MHz Dipole Magnet

For filling the Antiproton Accumulator ring, the beam in the PS must be concentrated within one quarter of its circumference. A first step is to inject as much beam as possible into two groups of five PS buckets each occupying one quarter of its periphery. For this purpose, beams from the 4-ring injector synchrotron (PSB) are recombined in pairs by means of an RF dipole magnet which permits longitudinal interleaving of successive bunches. Each PSB bunch being slightly under 180° in length, two of them can fit into a (stationary) PS bucket. It is shown that the use of a sinusoidal deflecting field instead of the ideal square wave results in only a modest growth of the transverse emittance of the recombined beams. The increase of longitudinal emittance by a factor of ~ 3, inherent to the scheme is also acceptable for the PS machine. We discuss the beam dynamics aspects, the construction of the 8 MHz, 250 gauss meter deflecting magnet and the experimental results.