| |
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 μm resolution are performed.
The data acquisition is synchronised to a single, flat 1 μs, 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 and 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.
|
|