BESSY II launches New Filling Pattern in User Mode

The new filling pattern consists of a Hybrid (or Camshaft) bunch at 4 mA (Chopper) in the center of the 200 ns wide ion clearing gap followed by the so-called PPRE-bunch of variable transverse excitation at 3 mA and 84 ns later. Together with the usual multibunch filling and the 3 slicing bunches on top of the multibunch train, now 302 out of 400 possible buckets in the storage ring are filled and topped up. © HZB

Since July 2015 BESSY II has been providing a new bunch filling pattern in Top-Up mode. It will open new opportunities especially for research teams dealing with time-resolved x-ray experiments. It is of significant importance for us and the community anticipating BESSY VSR.

Apart from ultrafast experiments at the Femtoslicing facility (slicing bunches) and x-ray pump-probe applications with the hybrid (or camshaft) bunch, now also time-of-flight experiments with the ARTOF and other instruments that use the pulse selection of the MHz-Chopper [1]  can be carried out in normal mode.

The new additional bunch in the dark gap arriving 84 ns after the chopper bunch can be transversally excited to support time-resolved Photoelectron- and X-ray spectroscopy based on the PPRE-technique [2]. Having such time-resolved methods at hand in the regular usermode we are even now able to take a glimpse into future operation modes at BESSY VSR.