Operating Modi BESSY II
Multi Bunch Hybrid Mode
In the Multi Bunch Hybrid Mode - our standard operation mode - 350 RF buckets out of 400 available buckets are filled with electrons (up to 0.9 mA per electron bunch). In the gap a single bunch (10 mA) is injected for pump-probe experiments using the fs-slicing facility.
Multi Bunch 3+1 Hybrid Mode
The Multi Bunch 3+1 Hybrid Mode is our standard operation mode for femtosecond slicing operation (-> femtoslicing). This mode is based on the standard hybrid mode, with additional three pulses, separated by 12 ns each. A total of 280 mA is stored in the multi bunch train, the single bunches carry a maximum of 5 mA each.
Single Bunch Operation
In Single Bunch Operation only one bucket is populated with electrons. The photon pulse derived from this bunch returns every 800 ns (exactly 800.5515 ns) according to the ring energy and the circumference. The purity of this single bunch, i.e. the ratio of electrons in the bunch to the number of electrons in other bunches, is > 10^4. Single bunch operation is a unique tool for time-resolved experiments. We offer two weeks of Single bunch operation twice a year with a bunch current of 20 mA.
Low-alpha Multi Bunch Hybrid Mode
In the Low-alpha Multi Bunch Hybrid Mode the momentum compaction factor is modified to smaller values by a special setting of the electron optics of the storage ring. Thus, the lengths of the electron bunches are decreased giving rise to coherent synchrotron radiation in the THz spectral region. Also, the photon pulse lengths are shortened, 1-2 ps compared to 30 ps in normal modes, providing an option for time-resovled studies by using the hybride bunch. Currently, we offer low-alpha operation four times a year for three days with 0.1 mA per bunch for all bunches.
