Improved Recombination of the 20 PSB Bunches and Merging into 5 Dense Bunches in the CERN Proton Synchrotron

Different combinations of the beams from the 4 CERN Proton Synchrotron Booster (PSB) rings allow several PS injection schemes. Up to now, the 20-bunch-to-bucket transfer which brings sequentially to the PS level the beams from the 4 superposed PSB rings (Fig. 1a) has been used in operation. This transfer mode has recently been adapted to the higher intensity beam delivered by the new Linac. Last year two new modes of combining the 4 PSB beams were achieved to provide a high line density for p¿ production on a cycle-to-cycle change basis: i) beams from two PSB rings are simultaneously ejected and vertically added in the transfer line and similarly for the other two rings leading to the so-called 10 bunch mode (Fig. 1b); ii) a further gain in line density is obtained by the 5 bunch mode (Fig. 1c): each of the two double beam batches is ejected from the PSB at a slightly different energy, trapped in five PS buckets after azimuthal shift and accelerated up to high energy.