BREAKING NEW GROUND WITH HIGH RESOLUTION TURN-BY-TURN BPMS AT THE ESRF

This High-Resolution, Turn-by-Turn BPM system is a low-cost extension to the existing BPM system, based on the RF-multiplexing concept, used for slow Closed-Orbit measurements. With this extension Beam Position measurements in both planes, at all (224) BPMs in the 844 m ESRF Storage Ring, for up to 2048 Orbit Turns with 1 micrometer resolution are performed. The data acquisition is synchronised to a single, flat 1 uS, transverse deflection kick to the 1µs beamfill in the 2.8µs revolution period. The high quality of this synchronisation, together with the good reproducibility of the deflection kick and the overall stability of the Closed Orbit beam allows to repeat the kick & acquisition in many cycles. The subsequent averaging of the data obtained in these cycles yields the 1um resolution. The latter allows lattice measurements with high precision such as the localisation of very small focussing errors and modulation in Beta values and phase advances. It also finds an unique application to measure, model, and correct the (H to V) Betratron coupling which recently showed successfully the reduction of coupling and vertical emittance below respectively 0.3 % and 12picometer.rad. This method takes full benefit from 64 BPM stations situated around 32 straight-sections (no focussing elements) of 6m length allowing the phase-space measurements in their centers