Beam Position Measurement for Proton-Antiproton Operation in the SPS

New beam monitors and receivers have been constructed for the position measurements of the colliding pp beams in the SPS. The directional coupler has been chosen as monitor for its accuracy, directivity and simple construction. Due to the directivity of the coupler, the beam position can be measured separately, for p and p beams, even in the zone of interaction. The new superheterodyne 200 MHz receiver and synchronous detector are capable of measuring the beam position of single bunches, shorter than 5 ns at intervals of > 1 μs, as well as continuous beams bunched at 200 MHz CW. The same system can be used both in the transfer lines and in the ring, for single passage or closed orbit measurements of all or individual single bunches. The resolving power of the position measurement amounts to 0.02 mm, as was demonstrated by beam tests. Momentum differences Δp/p ≥ 5.10−5 can be detected between different bunches at injection.